Si photonics: past, present, and future
Author(s):
Kazumi Wada
Show Abstract
This paper has three sections on computation revolutions in the information age. In the first section key examples of
revolutions in the early history, i.e., how to overcome heat penalty arisen from high power consumption in silicon
electronics will be presented to bring to light in the ever evolving nature of the computation. In the second section the
optical interconnection in terms of silicon photonics will be discussed as the way in which computation have
fundamentally altered the previous trend of power consumption. The final section will focus on a paradigm shift in
computation, i.e., an architecture of logic implementation, binary decision diagram, to replace to current computation
system without fighting transistor logic circuitry.
Micro/nano scale silicon based photonic devices
Author(s):
Zhiping Zhou
Show Abstract
Recent progresses in silicon-based micro/nano photonic devices and optoelectronic integration are summarized, including Si-based light sources, waveguide devices, modulators, detectors and integration attempts. Surface plasmons, photonic crystals and other methods to realize these devices are described. The potential and possibility to realize all-silicon devices and monolithic integration or make the fabrication compatible with standard CMOS process are presented and discussed, and their applications in high density data communications are emphasized.
Ge nanostructures doped silica-on-silicon waveguides
Author(s):
Haiyan Ou;
Troels Peter Rørdam;
Karsten Rottwitt;
Flemming Grumsen;
Andy Horsewell;
Rolf W. Berg;
Peixiong Shi;
Lionel Cervera Gontard;
Rafal E. Dunin-Borkowski
Show Abstract
Ge nanostructures embedded in silica matrix are emerging as a promising material for new generation devices due to the
unique electric and photonic properties. In this paper, Ge nanoclusters and nanocylinders with Ge shell were successfully
formed by the high energy electron irradiation in the PECVD deposited glass. In addition, large area Ge nanoclusters
were also created by heat-treatment of PECVD deposited glass film. These nanostructures were characterized in terms of
size, composition, distribution and crystalline state by using TEM, HRTEM, EDS, SEM, Raman spectroscopy, and
SIMS. Waveguides doped with Ge nanoclusters were fabricated and their absorption has been characterized in a
wavelength range from 500nm to 1700nm.
Photonic buffer memory based on polarization bistability in VCSELs
Author(s):
Hitoshi Kawaguchi
Show Abstract
A novel photonic buffer memory with a shift register function is proposed. The buffer memory consists of a two-dimensional
array of polarization bistable vertical-cavity surface-emitting lasers (VCSELs), in which the bit state of the
optical signal, "0" or "1" is stored as a lasing linear polarization state of 0 or 90°. Input data stored as the polarization
states of the first VCSEL are transferred to the polarization states of the second VCSEL. In our experiment using 980
nm VCSELs, 10 Gbit/s optical buffering, 2-bit optical buffering, and a shift register function have been successfully
demonstrated.
40Gb/s all-optical digital encoder/comparator based on semiconductor optical amplifiers
Author(s):
Yang Wang;
Xinliang Zhang;
Jianji Dong;
Dexiu Huang
Show Abstract
We proposed, experimentally and theoretically demonstrated all-optical two line-four line encoder and two bit-wise
comparator of RZ data streams at 40Gb/s based on cross gain modulation (XGM) and four wave mixing (FWM) in
three parallel SOAs. Five logic functions for digital encoder and comparator between two signals A and B: A¯ B¯,
AB¯, AB¯, AB and A¯⊗¯B¯, were achieved simultaneously. The first three optical logics are realized based on XGM in
SOAs, the fourth is realized with FWM, and the fifth is the mixing result of the first and the fourth. A detuning filter is
employed to improve the output performance. The output extinction ratio (ER) for the XGM operation is above 10dB,
and the ER for FWM operation is around 8 dB. Wide and clear eye patterns for the five logic outputs can be observed.
The all optical digital encoder/comparator we demonstrated has advantages of simple structure, multifunctional optical
logic functions and high speed.
Investigation of ultrafast all-optical AND gate based on cascaded SOAs and optical filters
Author(s):
Jing Xu;
Xinliang Zhang;
Jianji Dong;
Deming Liu;
Dexiu Huang
Show Abstract
We propose an ultrafast all-optical logic AND gate based on two cascaded SOA-OF configurations. Each SOA-OF consists a semiconductor optical amplifier (SOA) followed by an optical filter (OF) which reshapes the spectrum of the modulated probe light. A delayed interferometer (DI) and a tunable band pass filter (TNBPF) are chosen as OFs in the first and second SOA-OF. 40Gbit/s AND operation with 33% duty cycle return-to-zero (RZ) signals has been successfully demonstrated with SOAs whose 10%~90% recovery time are measured much larger than the time duration of one bit period. The quality factor (QF) and the extinction ratio (ER) of the eye diagram of the derived AND results were 6.3 and 8.8dB respectively. Numerical analysis and experimental demonstration with 40Gbit/s nonreturn-to-zero (NRZ) signals is also presented and shows that in order to achieve good AND result at the second stage, the differential time delay of the DI must be shorter than the single bit period of the input signals. The proposed AND gate takes the advantage of high speed WC realized by SOA-OF which displays flexibility to various data rates, pulse width as well as data formats.
Analysis of femtosecond self-polarization modulation in semiconductor optical amplifier
Author(s):
Mao-tong Liu;
Ai-ying Yang;
Yu-nan Sun
Show Abstract
Based on a three-band model, a new theoretical model is derived to describe the self-polarization modulation (SPolM)
effect in semiconductor optical amplifier (SOA) on femtosecond time-scale. In the case of SPolM, the phase difference
between the TE and the TM modes is created by the signal itself and results in changes of polarization states of the signal.
Numerical experiments are carried out to analyze the gain and the signal induced phase shift when an ultrashort optical
pulse injected into a tensile strained SOA. The higher injected power can induce a larger phase shift. The
polarization-dependent effect has much more influences on strong optical pulses.
1.55 μm extremely efficient and polarization insensitive tunable Mach-Zehnder wavelength duplexer based on an InGaAsP/InP ridge waveguide structure
Author(s):
L. Xu;
X. J. M. Leijtens;
M. J. H. Sander-Jochem;
T. de Vries;
Y. S. Oei;
P. J. van Veldhoven;
R. Nötzel;
Meint K. Smit
Show Abstract
A tunable Mach-Zehnder wavelength duplexer has been realized based on P-i-n-N InGaAsP/InP. It has been
made polarization insensitive by proper wafer layer stack and proper waveguide geometry. The layer stack for
the duplexer was tested first with a waveguide phase shifter, which resulted in up to 36°/(V•mm) phase shifting
efficiency for TE polarization, which is slightly more efficient than the most efficient phase shifter reported to
date in bulk InP at 1.55 μm, and with much lower transmission loss[1]. The transmission loss was measured to
be 4 dB/cm (5 dB/cm) for TE (TM) polarized light, for 2 μm wide shallowly etched waveguides, which is rather
low compared to other reported high efficiency phase shifters for this material system. With this layerstack, we
designed a Mach-Zehnder (MZ) duplexer with narrow, 1.5 μm wide, deeply etched phase shifters that meet the
polarization insensitivity requirement. The measurement results showed that the phase shifting efficiency of this
narrow and deeply etched duplexer is up to 34°/(V•mm) for both TE and TM polarization, and the transmission
loss of this 1.5 μm wide waveguide is about 10 dB/cm for both TE and TM polarization. This is also the first
reported deeply etched narrow phase shifter with high phase shifting efficiency and relatively low loss.
Ultrafast multifunctional all-optical logic gates based on single semiconductor optical amplifier
Author(s):
Jianji Dong;
Xinliang Zhang;
Songnian Fu;
Yang Wang;
Dexiu Huang
Show Abstract
We propose and demonstrate 40Gb/s multifunctional all-optical logic gates based on single semiconductor optical
amplifier (SOA) and a blue shifted optical bandpass filter (OBF), suitable for both return-to-zero (RZ) and nonreturn-to-zero
(NRZ) format. The logic functions NOT, NOR and OR of RZ format are realized at the OBF detuning of -0.15nm, -
0.22nm, and -0.44nm, respectively. The logic functions NOT and NOR of NRZ format are realized at the OBF detuning
of -0.24nm. The measured ER is around 7dB and Q factor is over 6. Our scheme has the potential advantages of multilogic
functions, simple structure, and high tolerance to input pulsewidth.
Electrooptic properties of InGaAsP-based asymmetric double quantum well electroabsorption modulators
Author(s):
Dong Kwon Kim;
D. S. Citrin
Show Abstract
Theoretical calculations of the optical properties of InGaAsP quantum well (QW) electroabsorption modulators (EAM's)
operating at c-band (~1550 nm wavelength) is presented. Absorption coefficients of QW's are obtained from the linear
optical susceptibility. Excitons are calculated in momentum space, which includes valence-band mixing, mixing of
excitons originating in different subband pairs, and exciton spin-related optical selection rules. Various line-broadening
mechanisms relevant to InGaAsP-QW's are also included. Investigations on asymmetric double QW's (ADQW's) show
that the small-signal modulation efficiency, which is an important figure of merit for analog application, can be
enhanced significantly at substantially reduced operating bias voltage. Simple optimization of ADQW band structure
results in a maximum slope efficiency ~3.8 times larger than that of SQW EAM's at a reduced operating bias field of 34
kV/cm compared with ~70 kV/cm for comparable SQW's.
The spectral feature analysis of semiconductor thin disk laser
Author(s):
Chun-feng He;
Li Qin;
Jun Li;
Li-wen Cheng;
Xue-mei Liang;
Yong-qiang Ning II;
Li-jun Wang
Show Abstract
The semiconductor thin disk laser is a new type of semiconductor laser. This work gives the basic operation function
of semiconductor disk laser, and analyses the heat effect by the experimentally measured photoluminescence spectrum of
the laser chip at different pump power and different temperature. We can see that: with increasing pump power, the
thermal effects of the gain material becomes seriously and causes the saturation of carrier lifetime, so the electron-hole
pair created in the absorbtion layer have no enough time to rate to one of the wells, and the non-radiative recombination
happens in the barrier. When the thermal effects becomes stronger, the chip will not lasing. This phenomenon is from the
smaller energy offset between barrier and quantum well. We optimize the original structure design and experimental
technology. A non-absorbing AlGaAs layer who is transparent to the pumping and laser wavelength is added to confine
the carriers in the quantum wells. At the same time a DBR with double reflecting band is induced to improve the
absorbing efficiency of the pumping light. The single QW is replaced by the three narrow QWs, This three QWs
structure can add the quantum state of QW, increase the recombination probability of carriers in the QWs and reduce the
heat effect. The chemical etch equipment is also improved to control the surface unevenness to be within 50 nm.
Variable wavelength conversion based on fan-out grating in QPM-LN
Author(s):
Yiju Wang;
Yuanqing Huang;
Zihua Weng;
Huangping Yan;
Ruifang Ye;
Jiangong Zhu
Show Abstract
In this paper, we demonstrated for the first time variable 1.5μm wavelength conversion through cascaded second order
nonlinear processes "SHG+DFG" by fan-out grating in lithium niobate waveguide. We fabricated the waveguide by
annealed proton exchange in periodically poled LiNbO3 (PPLN). The device used in this experiment is 4 cm long, has a
QPM period from 14.8μm to 15.2μm, waveguide width of 12μm, proton exchange depth of 0.7μm, and was annealed for
32h at 350°C. After proton exchange in pure benzoic acid using a SiO2 mask, the substrate was annealed in an oxygen
atmosphere. The wavelength of signal light was set at 1551.3 nm. The wavelengths of tunable pump lights we used in
experiment were 1543.2 and 1556.2 nm, and the corresponding grating periods were 14.87 μm and 15.03 μm,
respectively. The temperature was set at 100.5°C to avoid photo refractive damage and to match the QPM peaks to the
pump wavelengths. The conversion efficiency was about 10dB to be expected with the pump power 175mW in a similar
device with a slightly different QPM period and operated at 125°C.
Design and fabrication of a novel monothically integrated dual-wavelength tunable photodetector
Author(s):
Jihe Lv;
Hui Huang;
Yongqing Huang;
Xiaomin Ren;
Ang Miao;
Yiqun Li;
Hongwei Du;
Qi Wang
Show Abstract
The design and fabrication of a Monothically integrated dual-wavelength tunable photodetector are reported.
The dual-wavelength character is realized by introducing a taper substrate. The photodetector operating on
long wavelength is Monothically integrated by using heteroepitaxy growth of InP-In0.53Ga0.47As-InP p-i-n
structure on GaAs based GaAs/AlAs Fabry-Perot filter structure, which can be tuned by thermal-optic effect.
High quality heteroepitaxy was realized by employing a thin low-temperature buffer layer. The integrated
device with a dual-peak distance of 7nm (1530nm,1537nm) , a wavelength tuning range of 5.0 nm, and a
3-dB bandwidth of 5.9 GHz was demonstrated, according with the theoretical simulation.
Multiplication characteristics of InP/InGaAs avalanche photodiodes with thick multiplication and charge layers
Author(s):
Yanli Zhao
Show Abstract
In this report, the multiplication characteristics of InP/InGaAs avalanche
photodiode (APD) with thick multiplication and charge layer have been studied
theoretically and experimentally, considering the electric field distribution, carrier
concentration, and different multiplication layer thickness. We find that ionization in
the charge layer is very sensitive to avalanche multiplication (M) and breakdown
voltage (Vbr). Partial ionization in the charge layer has been suggested, which gives a
good description of experimental results.
On the performance analysis and design of a novel shared-layer integrated device using RCE-p-i-n-PD/SHBT
Author(s):
Shou-li Zhou;
De-ping Xiong;
Ya-li Qin;
Hai-lin Cui;
Yin-zhe Chong;
Miao Ang;
Ji-he Lv;
Jun-hua Gao
Show Abstract
Abstract: We have explored the shared-layer integration fabrication of an resonant-cavity-enhanced
p-i-n photodector (RCE- p-i-n-PD) and a single heterojunction bipolar transistor (SHBT) with the
same epitaxy grown layer structure. MOCVD growth of the different layer structure for the GaAs
based RCE- p-i-n-PD/SHBT require compromises to obtain the best performance of the integrated
devices. The SHBT is proposed with super-lattice in the collector, and the structure of the base
and the collector of the SHBT is used for the RCE. Up to now, the DC characteristics of the
integrated device have been obtained.
InP-based optoelectronic components for all optical communication
Author(s):
Y. Baek;
D. K. Oh
Show Abstract
All optical communication era is finally about to start. Penetration of optical communications into the residential area is
under progress worldwide and the rate will be increased due to the bandwidth demanding services emerging consistently.
To accommodate all the rapid increases of optical network expansion, vast of optoelectronic components are necessary.
Costs and volume productions are key elements. One of the solutions is photonic integration which can reduce the cost of
labors and have the potential of large volume productivity. In this paper, several photonic integrated devices which are
currently under development in our lab are discussed.
InP-based long wavelength VCSELs: their characteristics and applications
Author(s):
N. Nishiyama;
C. Caneau;
M. Sauer;
A. Kobyakov;
C. E. Zah
Show Abstract
InP-based vertical cavity surface emitting lasers (VCSELs) with AlGaInAs QWs and AlGaInAs/InP DBR have been
demonstrated. Over 3 mW and ~1 mW powers at both 1.3 μm and 1.55 μm have been achieved at 20 °C and 85 °C,
respectively. Tests for various applications have been performed with our 1.3 and 1.55 μm VCSELs. Error free
transmission over 10 km under 10 Gbit/s, 85°C has been demonstrated with both 1.3 and 1.55 μm VCSELs. The effect of
electrical dispersion compensation (EDC) with 1.55 μm VCSELs has been confirmed for transmission of medium range
data transmission. Radio signal transmission with low error vector magnitude by 1.3 μm VCSELs has been achieved at 2.4
and 5 GHz-band radio frequency.
Moving from ultrafast VECSELs to MIXSELs: a new class of ultrafast semiconductor lasers
Author(s):
T. Südmeyer;
D. J. H. C. Maas;
A.-R. Bellancourt;
B. Rudin;
M. Golling;
H. J. Unold;
U. Keller
Show Abstract
We demonstrate wafer-scale integration of a saturable absorber in a surface emitting semiconductor laser. Vertical
external cavity surface-emitting lasers (VECSELs) have high quality circular output beams, 2D-array scalability, and
high average power. To date, ultrafast VECSELs required a folded cavity with a separate saturable absorber device for
passive modelocking. In the result presented here, we integrate the saturable absorber into the same semiconductor
wafer, optimize its performance for integration with quantum dots and demonstrate stable passive modelocking in a
simple straight external cavity which allows for a fully monolithically wafer-integrated structure to reduce cost and
improve ease of mass production. We refer to this class of devices as the modelocked integrated external-cavity surface emitting laser (MIXSEL). Such devices would be ideally suited for many applications where the current ultrafast laser technology is considered to be too bulky and expensive.
High power VCSEL device with periodic gain active region
Author(s):
Y. Q. Ning II;
L. Qin;
Y. F. Sun;
T. Li;
J. J. Cui;
B. Peng;
G. Y. Liu;
Y. Zhang;
Y. Liu;
L. J. Wang;
D. F. Cui;
Z. Y. Xu
Show Abstract
High power vertical cavity surface emitting lasers with large aperture have been fabricated through improving
passivation, lateral oxidation and heat dissipation techniques. Different from conventional three quantum well structure,
a periodic gain active region with nine quantum wells was incorporated into the VCSEL structure, with which high
efficiency and high power operation were expected. The nine quantum wells were divided into three groups with each of
them located at the antinodes of the cavity to enhance the coupling between the optical field and the gain region. Large
aperture and bottom-emitting configuration was used to improve the beam quality and the heat dissipation. A maximum
output power of 1.4W was demonstrated at CW operation for a 400μm-diameter device. The lasing wavelength shifted to
995.5nm with a FWHM of 2nm at a current of 4.8A due to the internal heating and the absence of active water cooling.
A ring-shape farfield pattern was induced by the non-homogeneous lateral current distribution in large diameter device.
The light intensity at the center of the ring increased with increasing current. A symmetric round light spot at the center
and single transverse mode operation with a divergence angle of 16° were observed with current beyond 4.8A.
Loss-reduced semiconductor ring lasers based on active vertical coupler structure and two-section rectangular cavity
Author(s):
R. Zhang;
O. Ansell;
Z. Ren;
S. Yu
Show Abstract
InGaAsP/InP rectangular ring lasers based on active vertical coupler structure are demonstrated in terms of loss-reduction.
Varied thresholds for different configuration devices with different coupling current have been
measured. The smallest threshold current of 75mA has been achieved in the device with the coupler length of
300μm and coupling current of 30mA. Such variation has also been calculated assuming different fabrication
loss. Their loss mechanisms have been investigated based on threshold analysis, which should benefit to further
optimize loss-reduced semiconductor polygon ring lasers based on active vertical coupler structure.
Optical gain in 407nm and 470nm InGaN/GaN heterostructures: signature of quantum-dot states
Author(s):
B. Witzigmann;
S. Steiger;
M. Tomamichel;
R. Veprek;
U. T. Schwarz
Show Abstract
In this contribution, a detailed analysis of optical gain in InGaN/GaN quantum structures with Indium content of 10%
and 20% is presented. Experimental data are obtained from
Hakki-Paoli characterization of edge-emitting Fabry-Perot
lasers. A gain model that includes many-particle effects on a microscopic level, as well as combined quantum-well and
quantum-dot density of states, is used to explain the experimental findings. Inhomogeneous broadening arising from
local Indium clusters is included via a statistical fluctuation of the electronic density of states. Excellent agreement is
obtained for the characteristic gain spectra from structures emitting at 405nm (10% In content) and 470nm (20% In
content), and a systematic analysis of the microscopic physics shows signature of quantum-dot states.
Applications of swept light sources in imaging, sensor, and tests
Author(s):
Tongning Li;
Yibing Tang;
Wenchao Xu;
Qinian Qi;
David Eu
Show Abstract
A swept light source is a type of light source whose wavelength can be quickly tuned . Typically, a swept light source is
composed of a high optical gain-medium such as a semiconductor optical amplifier (SOA) or optical gain module and a
wavelength selective component. Inphenix has developed swept light sources that cover from 800nm to 1550nm
wavelengths and are cost effective, highly linear and ideal for medical imaging and industrial measurement applications.
Applications of swept light sources have been widely investigated in real time optical imaging, optical fiber sensor
interrogator and optical component testing.
Design and fabrication of high-performance InGaAsP/InP electroabsorption modulator
Author(s):
Hua Yang;
Mee Koy Chin;
Desmond C.S. Lim;
Jingtao Zhou;
Shuhying Lee;
Yuanbing Cheng;
HongLiang Zhu;
Weixi Chen
Show Abstract
Electroabsorption modulator has been widely used in modern optical fiber communication system and analog RF link system. In this paper, the design of a high-performance EAM with low coupling loss, high saturation power and high speed was demonstrated, which include the waveguide, active core and electrodes. A novel EAM with large optical cavity (LOC) waveguide structure, intrastep quantum well (IQW) active core and traveling wave electrodes was presented and fabricated successfully. Our results show that the LOC waveguide effectively improved the optical profile of EAM and reduced the coupling loss. The obtained traveling wave EAM achieved 21dBm saturation power and 23GHz 3-dB bandwidth.
Nano-structured special quantum well for high-performance optical modulators
Author(s):
Taro Arakawa;
Kunio Tada
Show Abstract
A five-layer asymmetric coupled quantum well (FACQW) is a novel potential-tailored quantum well that is expected to
exhibit giant electrorefractive (ER) index change in a transparency wavelength region. We studied the GaAs/AlGaAs
and InGaAs/InAlAs FACQW theoretically and experimentally. A GaAs/AlGaAs FACQW was grown by molecular
beam epitaxy (MBE). Giant ER sensitivity |dn/dF| as large as 1.7 × 10-4 cm/kV was observed in the FACQW phase
modulator. A Mach-Zehnder (MZ) FACQW modulator was fabricated and the operation voltage was successfully
decreased. For 1.55 μm wavelength region, an InGaAs/InAlAs FACQWs was also proposed and studied. We found that
the InGaAs/InAlAs FACQW is also expected to produce a giant ER sensitivity |dn/dF|. The InGaAs/InAlAs multiple
FACQW was successfully grown by MBE and the results of its photoabsorption current measurements are consistent
with the theory. We proposed an MZ modulator and a 2 × 2 switch with the multi-FACQWs in the core. Driving voltages
of the FACQW modulator and the switch with 1mm-long phase shifters can be decreased as low as 0.1~0.2 V.
Design and performance of monolithic integrated electro-absorption modulated distributed feedback laser
Author(s):
YuanBing Cheng;
JiaoQing Pan;
Fan Zhou;
BaoJun Wang;
Hongliang Zhu;
Lingjuan Zhao;
Wei Wang
Show Abstract
High performance InGaAsP/InGaAsP strained compensated multiple-quantum-well (MQW) electroabsorption
modulators (EAM) monolithically integrated with a DFB laser diode have been designed and realized by ultra low
metal-organic vapor phase epitaxy (MOVPE) based on a novel butt-joint scheme. The optimization thickness of upper
SCH layer for DFB and EAM was obtained of the proposed MQW structure of the EAM through numerical simulation
and experiment. The device containing 250μm DFB and 170μm EAM shows good material quality and exhibits a
threshold current of 17mA, an extinction ratio of higher than 30 dB and a very high modulation efficiency (12dB/V)
from 0V to 1V. By adopting a high-mesa ridge waveguide and buried polyimide, the capacitance of the modulator is
reduced to about 0.30 pF corresponding to a 3dB bandwidth more than 20GHz.
Silicon based ultra-compact modulator with photonic crystal
Author(s):
Ran Hao;
An Mao;
Junbo Feng;
DingShan Gao;
Zhiping Zhou;
David S. Citrin
Show Abstract
We describe two Si based optical-electric modulators based on photonic crystals (PC), which are capable of monolithically integrated with Si photonic integrated circuits. One is a modulator based on Mach-Zehnder interferometer (MZI), the other is a modulator based on photonic band gap. These devices may enable the deployment of ultra-compact (-200 μm) devices with high extinction ration and low insertion loss.
Negative refraction and birefringence in a two-dimensional flat perfect photonic crystal
Author(s):
Zhuo Li;
Binming Liang;
Hanming Guo;
Jiabi Chen;
Songlin Zhuang
Show Abstract
A new kind of birefringence is found in a two-dimensional (2D) flat perfect photonic crystal (PhC). It is different from
the one in the normal biaxial crystal, but qualitative, and comes from the positive and negative refraction in the 2D flat
perfect PhC. The quantitative relationship between the refractive index and the incident angle are plotted, by the analysis
of the equal-frequent surface (EFS) of the perfect PhC. The plot is consisted of three branches---the main across 0° to
45.53° of the incident angle, the upper across 33.3° to 38.53° and the lower across 38.53° to 45.53°. The upper reveals the
positive refraction; the lower and the main reveal the negative ones. The finite-difference time-domain (FDTD)
simulations are performed, and the relevantly quantitative measurement validates the quantitative relationship by the
analysis of the EFS, but a 2.67° shift to the bigger incident angle.
A novel beam guiding is observed, which is resulted not from the guiding in a defect photonic crystal (PhC) but from the
negative refraction in a two-dimensional (2D) flat perfect PhC slab.
Broad-band local field enhancement of a 2D nano-cavity
Author(s):
Xiao-xing Su;
Feng Liu;
Juan Liu;
Shui-sheng Jian
Show Abstract
We investigate the local field enhancement properties of a 2D nano-cavity by using finite-difference
time-domain (FDTD) method. The 2D nano-cavity is built by two pieces of silver slabs with periodical
subwavelength corrugations on their inner boundaries. Numerical simulation result shows that the 2D
nano-cavity can confine and enhance light field within the region smaller than the diffraction limit in a relatively
broad range of wavelength. The result is useful for the research and development of new kinds of broadband
optical sources used in WDM optical communication networks or micro-optical sensor system.
Wide-band transmission of slow light in one-dimensional photonic crystal coupled resonator optical waveguide
Author(s):
Changhong Li;
Huiping Tian;
Bin Liu;
Yuefeng Ji
Show Abstract
Transmission properties of slow light in one dimensional photonic crystal coupled resonator waveguide have been
investigated. By inserting multiple half-wavelength cavities discretely to forming CROW, the slow light band in
photonic crystal bandgap can be broadened effectively. Otherwise cavities distance and refractive difference can flatten
the rough pass band. By modulating these parameters, an optimized broadened flat pass band with 20.99nm has been
obtained. Within the band, the group velocity is in the range of 0.0142c to 0.02148c. The propagation mechanism has
been investigated via analysis of the field distribution in CROW.
Continuous-wave optical fiber based supercontinuum light source
Author(s):
Z. G. Lu;
Y. Song;
J. R. Liu;
X. P. Zhang
Show Abstract
We have demonstrated a continuum-wave (CW) supercontinuum (SC) fiber light source with over 1000 nm bandwidth
based on a low-cost erbium/ytterbium co-doped double-cladding fiber ring cavity laser. Based on the observation to the
SC evolvement, we have experimentally analyzed the detailed contributions of several nonlinear effects within highly
nonlinear dispersion-shifted fiber (HNLF). Our experimental results have clearly indicated that four-wave mixing (FWM)
and stimulated Raman scattering (SRS) play key roles in CW-pumped SC generation. At the same time, self-phase
modulation (SPM) mainly contributes to generate new frequency components near the peaks that appear in the form of
the spectra broadening while cross-phase modulation (XPM) enhances the broadening of peaks.
Hybrid mode-locking based on nonlinear polarization rotation in a SOA fiber ring laser
Author(s):
Fei Wang;
Xin-Liang Zhang;
Zheng-Mao Wu;
Guang-Qiong Xia
Show Abstract
A hybrid actively and passively mode-locking semiconductor optical amplifier fiber ring laser based on nonlinear
polarization rotation was presented, where intensity modulator not only acted as modulator but also polarizer. Under the
hybrid mode-locking mechanism, output pulse is with some new characters. So, a theoretical model that describes the
SOA fiber ring laser was developed and system parameters effects on mode-locking pulse are discussed.
Liquid crystal photonic bandgap fiber components
Author(s):
L. Scolari;
T. T. Alkeskjold;
D. Noordegraaf;
G. Tartarini;
P. Bassi;
A. Bjarklev
Show Abstract
Liquid crystal photonic bandgap fibers represent a promising platform for the design of all-in-fiber optical devices,
which show a high degree of tunability and exhibit novel optical properties for the manipulation of guided light. In this
review paper we present tunable fiber devices for spectral filtering, such as Gaussian filters and notch filters, and devices
for polarization control and analysis, such as birefringence control devices and switchable and rotatable polarizers.
Field trial of 160 Gb/s all-optical packet switching
Author(s):
Y. Liu;
J. Herrera;
O. Raz;
E. Tangdiongga;
J. Marti;
F. Ramos;
G. Maxwell;
A. Poustie;
H. C. H. Mulvad;
M. T. Hill;
H de Waardt;
G. D. Khoe;
A. M. J. Koonen;
H. J. S. Dorren
Show Abstract
We present the results of a transmission experiment, over 110 km of field installed fiber, for an all-optical 160 Gb/s
packet switching system. The system uses in-band optical labels which are processed entirely in the optical domain
using a narrow-band all-optical filter. The label decision information is stored by an optical flip-flop, which output
controls a high-speed wavelength converter based on ultra-fast cross-phase modulation in a single semiconductor optical
amplifier. The packet switched node is located in between two different fiber sections, each having a length of 54.3-km.
The field installed fibers are located around the city of Eindhoven in the Netherlands. The results show how the all-optical
switch can effectively route the packets based on the optical information and that such packets may be
transmitted across the fiber with an acceptable penalty level.
Theoretical analysis of nonlinear polarization rotation influence on optical sampling in semiconductor optical amplifier
Author(s):
Mao-tong Liu;
Ai-ying Yang;
Yu-nan Sun
Show Abstract
Based on a three-band model, a polarization-dependent pulsed
four-wave mixing (FWM) model which can be used to
analyze the optical sampling process in semiconductor optical amplifier (SOA) is presented. The polarization-dependent
characteristics and cross-polarization modulation (XPolM) of pump, probe and conjugate pulses are investigated in detail.
The maximum sampling efficiency occurs, when pump and probe pulses are linearly co-polarized and parallel to the TE
axis. When the pump, probe pulses with initial linear polarization states interacting in an SOA, their polarization states
do not just rotate and the conjugate pulse is not just linearly polarized but with complicated polarization states during the
propagation along the length of SOA.
Design of all-optical UWB monocycle generation for UWB-over-fibre communications
Author(s):
Jianji Dong;
Xinliang Zhang;
Jing Xu;
Dexiu Huang
Show Abstract
We propose and demonstrate a novel approach generating ultrawideband (UWB) monocycle pulses using cross phase
modulation (XPM) of the semiconductor optical amplifier (SOA). A pair of polarity-reversed UWB monocycle pulses is
achieved by locating the probe carrier at the positive and negative linear slopes of the filter. We achieve different UWB
spectrum width by 25ps- and 50ps-width Gauss pulse injection. The generated monocycle pulses can be controlled by
either optical Gauss pulse or both injections, which function as logic OR-monocycle. It has potential applications in
UWB-over-fiber communications.
A simple approach of high-purity millimeter-wave signal photonic generation
Author(s):
Tianliang Wang;
Minghua Chen;
Hongwei Chen;
Shizhong Xie
Show Abstract
A simple method of optical generation millimeter-wave signal employing optical phase modulator and band-elimination
filter is proposed. This simple approach is capable generate millimeter wave signal of quadrupled or sextuple microwave
source frequency with extremely high spectral purity. Millimeter-wave signal 26GHz (quadrupled fundamental
frequency) or 39 GHz (sextuple fundamental frequency) is obtained respectively using different system chromatic
dispersion when the microwave driver signal is at 6.5GHz.
Widely tunable lasers based on mode-hop-free semiconductor laser array
Author(s):
T. Kurobe;
T. Kimoto;
K. Muranushi;
T. Mukaihara;
M. Ariga;
T. Kagimoto;
N. Kagi;
N. Matsuo;
A. Kasukawa
Show Abstract
Integration of mode-hop-free tunable laser array and a semiconductor optical amplifier is most reliable approach to
realize widely tunable lasers. We have developed two types of tunable lasers, one is a thermally tunable DFB laser array
for DWDM tunable transponders, which has shown high power and wide tunability covering Cband or L-band, housing
in compact butterfly packages with robust wavelength locker. Another is a short-cavity DBR laser array for optical burst
switching, whose lasing frequency can be monotonously tuned and locked on the ITU grid within 5 microseconds. Both
lasers have demonstrated superior performances in system experiments.
Automated chip-on-carrier screening of a SOA integrated full band tunable laser (DSDBR)
Author(s):
Chao Wang;
George Dimitropoulos;
Andrew J. Ward;
Guoyuan Yang;
Xuming Wu
Show Abstract
Chip-on-carrier (CoC) sub-assemblies of Digital Ssupermode DBR (DSDBR) lasers are produced in high volume within
Bookham manufacturing plants. These lasers can cover more than 100 ITU channels with a 50GHz channel range across
the C or L band with a minimum 13dBm output power and 40dB side mode suppression ratio (SMSR). To guarantee a
high quality and ensure a good yield, an automated screening process has been put in place at the CoC level to eliminate
poor devices. Typical tuning maps and key performance features of the device are shown in this paper. We describe the
general features of the tuning map, and indicate how a suitable operating point can be determined. The use of automated
test kit is also described in this article. Finally, the performance of our device is presented in detail.
Static properties of widely tunable external cavity semiconductor laser with sampled fiber grating
Author(s):
Xiaoying He;
Yonglin Yu;
Dexiu Huang;
D. N. Wang
Show Abstract
Widely tunable external cavity semiconductor lasers with sampled fiber gratings are investigated. Their static properties,
such as threshold gain, tuning characteristic, emitting light spectrum, and side mode suppression ratio, have been
simulated and discussed by a combined theoretical model, which is developed to match experimental results. Up to
thirteen tunable channels can be obtained in this laser with high side-mode suppression ratios by tuning the injection
current of the passive phase control section. With the decrease of AR-coating reflectivity, the narrow line-widths, wide
tuning range, and high threshold gain in those tunable external cavity semiconductor lasers have been presented.
Theoretical model and simulation of the extremely short external cavity semiconductor laser
Author(s):
Guangqiong Xia;
Zhengmao Wu;
Jiagui Wu;
Zhaoyun Li;
Qi Yang;
Bingxing Yang
Show Abstract
Based on the ray tracing method, the implicit expression of the output spectrum of the extremely short external cavity
semiconductor Laser (ESECSL) is derived, and the output spectrum and P-I characteristic of the ESECSL are
investigated. The results show that: when the length of external cavity is changed at the order of wavelength, the P-I
characteristics of the ESECSL will undergo significant changes; with the variation of the external cavity length, the
lasing wavelength of ESECSL will behave cyclical jump in the range of 10nm. Especially, for the external cavity length
changed within the range of 40μm-70μm, the jump range of the lasing wavelength will reach the maximum. The
simulations well agree with the experimental results reported.
Trend and applications of tunable semiconductor lasers
Author(s):
San-Liang Lee;
Yen-Ting Pan;
Yung-Jr Hung;
Chiu-Lin Yao;
Chun-Hung Cheng;
Shuen-Te Ji
Show Abstract
Tunable semiconductor lasers have been under intense research interests for the past decades due to their vast
applications in optical networks, optical characterization, and optical sensing. The required device characteristics can be
very different for applying the tunable lasers to various areas. We classify the tunable lasers in terms of their tuning
characteristics and switching speed. Four kinds of tunable lasers are described in this paper to manifest the
application-dependent device structures and performance. The applications include the use of sampled grating based
lasers to form multi-wavelength laser arrays, cascaded distributed-feedback lasers for multi-gas sensors,
wavelength-selectable laser arrays for fast wavelength switching sources, and short cavity lasers for fault monitoring in
passive optical networks.
Advanced component technologies for colourless access networks
Author(s):
Christophe Kazmierski;
Philippe Chanclou;
Jose A. Lazaro
Show Abstract
In this paper we review our recent works on low cost lasers and remote modulators for Optical Network Unit in access
network. Our work is carried out in the context of an FTTH PON migration scenario towards 10Gbit/s base rate as well
as towards more capacity and flexibility using WDM technology. All components are based on the attractive thermal,
gain and absorption properties of AlGaInAs/InP material system. As a first step to the speed increase we propose a new
uncooled 10Gb/s laser based on a self thermal compensation principle. As a next step, new WDM PON architectures will
require wavelength agnostic component for ONU. For this purpose, we demonstrate new colorless concepts on 10Gb/s
remote amplified electro-absorption modulators. We show low-cost FTTH components may also be attractive for
emerging access-metro WDM technology introducing colorless principle in reconfigurable add and drop multiplexers
Cost-effective telecom/datacom semiconductor lasers
Author(s):
Nong Chen;
Dick T. R. Chen;
Wei Hsin;
Steven Bo Chen;
Frank Xiong;
Hernan Erlig;
Paul Chen;
Xian-li Yeh;
David C. Scott;
Axel Sherer
Show Abstract
The recent development of semiconductor laser technologies for
cost-effective telecom/datacom applications is reviewed
in details in this paper. This includes the laser design, laser chip technology, laser packaging technology and other low
cost lasers (chip + packaging). Some design and simulation examples in Archcom laser production are described first. A
latest trend in the wafer scale testing/characterization/screening technology for low cost semiconductor laser mass
production is discussed then. An advanced long wavelength high power single mode surface emitting laser with wafer
scale characterization using our unique mask free focused ion beam (FIB) etching technology is also demonstrated.
Detailed descriptions on our wide temperature range (-50 °C to +105 °C) G-PON distributed feedback (DFB)
semiconductor lasers with high performance and low cost wafer design are included. Cost reduction innovations in laser
package with our beam profile improved laser and optical feedback insensitive (OFBI) laser are also addressed.
980 nm pump laser module with 750 mW output power
Author(s):
Bing (Bruce) Guo;
Jinbo Lin;
Qin (Dylan) He;
Simon Loten;
Jeffery Greatrex;
Hans-Ulrich Pfeiffer;
Stefan Mohrdiek;
Tomas Pliska
Show Abstract
A new generation 980 nm pump laser module with a fiber output power more than 750 mW is
presented. The module uses our generation-08 (G08) pump laser chip, which is designed for high
output power and high reliability. The pump laser is stabilized by a fiber Bragg grating (FBG). A
special thermo-electric cooler (TEC) is built into the package in order to enable operation of the device
at high laser output powers.
Design of taper coupler for effective laser and single mode fiber coupling with large tolerance
Author(s):
Jing Zhang;
V. Ramana Pamidighantam;
John Hon-Shing Lau;
Qingxin Zhang;
Chandrappan Jayakrishnan;
Chee Wei Tan;
Ming Chinq Jong;
Teo Wei Liang Calvin;
Dim Lee Kwong
Show Abstract
A new method of coupling the light from a laser diode to a Single Mode Fiber (SMF) with large alignment tolerances
and without using coupling lenses is presented. A pseudo vertical tapered coupler is designed for light coupling between
laser diode and single mode fiber. It has a large input aperture which is about 100 times the size of the laser waveguide
cross-section. The tapered coupler provides single mode output and matches the mode size with the single mode fiber.
The tapered coupler is fabricated on a silicon optical bench and is located between the laser and the fiber through the
silicon micrfabrication process. The misalignment between the fiber and taper coupler can be very small since this is
controlled by high precision silicon optical bench patterning processes. The coupler relaxes the laser diode placement
accuracies and eliminates the need for a coupling lens. Design Studies showed that the tolerance between the laser diode
and taper coupler can be more than +/-5μm misalignment at x-y, and +/-0.5degree tilting angle tolerance and the
fabricated assembly results are encouraging with good placement tolerances and coupling efficiency. The laser to single
mode fiber coupling tolerances is greatly improved and passive alignment for laser and single mode fiber is realized. The
technology can be useful for multi channel optical assembly where significant device and process cost saving can be
achieved and is suitable for functional integration for silicon photonics.
Photonics studies on dilute nitrides at long wavelength for telecommunication
Author(s):
C. S. Peng;
M. Pessa
Show Abstract
By adding a little nitrogen in InGaAs / GaAs quantum well (QW), a strong bandgap-bowing in the QW is
caused. However, the incorporation of nitrogen results in lower photonuminescence intensity and wider line
width as a result of increased non-radiative centers. In order to increase the efficiency of radiative
recombination and hence reduce the laser threshold, a post-growth heat treatment has to be applied. Such kind
of heat treatment results in a big blue shift due to interdiffusion and other effects. During growth, in order to
incorporate nitrogen into InGaAs, the growth temperature is much lower than normal InGaAs growth. Large
number of point defects is induced under such low temperature. This is the main cause of the interdiffusion at
the interfaces of InGaAsN / GaAs QW. There are some other facts to cause the blue shift during heat
treatment, such as local neighbourhood redistribution called short range ordered. In our study, different blue
shift behaviors were clearly observed due to different blue shift mechanism. Post-growth heat treatment also
affects the laser performance dramatically. Lower temperature treatment mainly decreases the absorption loss
and higher temperature treatment improves the conductivity of the cladding layers. Different heat treatment
also results in very different burn-in behavior. An optimized heat treatment will be concluded after the
annealing discussion on laser devices. In order to assure longer emission wavelength well as higher
emission efficiency, many efforts have been tried and will be discussed in this paper.
Intersubband photonic devices by group-III nitrides
Author(s):
P. Holmström;
X. Y. Liu;
H. Uchida;
T. Aggerstam;
A. Kikuchi;
K. Kishino;
S. Lourdudoss;
T. G. Andersson;
L. Thylén
Show Abstract
The characteristics of intersubband transitions in III-nitride quantum wells are promising for detectors and all-optical
switches through a high intrinsic speed (~1 THz), and can also provide a high optical saturation power and a desired
small negative chirp parameter in electroabsorption modulators. The high LO-phonon energy allows to improve the
operating temperature of THz emitters. Recent achievements and prospects for intersubband III-nitride photonic devices,
mainly for λ=1.55 μm, are briefly reviewed. Further, means to enhance material quality by achieving crack-free growth
of GaN/AlN multiple-quantum-well (MQW) structures, and by employing intersubband transitions in multiple-quantum-disk
(MQD) structures incorporated into dislocation free GaN nanocolumns are discussed. We investigate the occurrence
of cracks in MBE-grown GaN/AlN MQWs on GaN MOVPE templates with respect to the buffer layer, the number of
QWs and the temperature reduction rate after growth. Intersubband absorption in GaN/AlN MQDs in the wavelength
range 1.38-1.72 μm is demonstrated in three samples grown on Si(111).
Design of a novel high-speed magneto-optic modulator
Author(s):
Jin Wan;
Yuanqing Huang;
Zihua Weng;
Huangping Yan;
Yiju Wang;
Zhaoxi Wu;
Ruifang Ye
Show Abstract
A novel high-speed magneto-optic (MO) modulator which consists of an integrated wire grid polarizer (WGP), Bi-YIG
waveguide with cladding layer and conducting micro-strip line is proposed. With the integrated WGP, this MO
modulator is faster, more accurate and more stable because it is not only completely driven by electric signals but also
has no mechanically moving parts. Moreover, it is compact-structured and low-cost. Large Faraday rotation is obtained
with specific arrangement of the directions of the bias magnetic field and the modulation RF magnetic field. Optical
route and optic-electrical detect circuit are also designed and analyzed.
Birefringent hollow core fibers
Author(s):
P. J. Roberts
Show Abstract
Hollow core photonic crystal fiber (HC-PCF), fabricated according to a nominally non-birefringent design, shows a
degree of un-controlled birefringence or polarization mode dispersion far in excess of conventional non polarization
maintaining fibers. This can degrade the output pulse in many applications, and places emphasis on the development of
polarization maintaining (PM) HC-PCF. The polarization
cross-coupling characteristics of PM HC-PCF are very
different from those of conventional PM fibers. The former fibers have the advantage of suffering far less from stressfield
fluctuations, but the disadvantage of a higher loss figure and the presence of interface roughness induced modecoupling
which increases in strength as birefringence reduces. Close to mode anti-crossing events of one polarization
mode, the PM HC-PCF is characterized by high birefringence, a high polarization dependent loss and an increased
overlap between the polarization modes at the glass interfaces. The interplay between these effects leads to a wavelength
for optimum polarization maintenance, λPM, which is detuned from the wavelength of highest birefringence. By a
suitable fiber design involving antiresonance of the core-surround geometry, λPM may coincide with a low-loss
wavelength for the signal carrying polarization mode.
Experimental demonstration of PPLN-based double ring fiber laser and its application to 40 Gb/s wavelength conversion
Author(s):
Jian Wang;
Junqiang Sun;
Qizhen Sun
Show Abstract
We report a novel double ring fiber laser incorporating a periodically poled LiNbO3 (PPLN) waveguide. The double ring
fiber laser is formed by placing two parallel-arranged tunable filters (TFs) followed by two variable optical attenuators
(VOAs) inside the PPLN-based fiber ring cavity. Two continuous-wave (CW) lasing lights can be obtained from the
double ring fiber laser with their wavelengths determined by two tunable filters. Using cascaded second-harmonic
generation and difference-frequency generation (SHG+DFG), as one of the lasing waves is tuned at the quasi-phase
matching (QPM) wavelength of PPLN, the third idler wave is generated. It is easy to perform tunable operation simply
by changing the other lasing wavelength. Based on cascaded sum- and difference-frequency generation (SFG+DFG), it is
also possible to realize tunable wavelength conversion. Both input signal and converted idler can be tuned by
appropriately adjusting two lasing waves. With PPLN-based double ring fiber laser, we first demonstrate stable dual-wavelength
generation with minimum wavelength spacing of 0.32 nm. Then we observe SHG+DFG-based tunable
triple-wavelength generation. Finally, tunable wavelength conversion at 40 Gb/s based on SFG+DFG is successfully
demonstrated in the experiment. No external CW optical waves are needed, which effectively reduces the complexity
and cost of the wavelength converter.
Light waveguide electro-optical printed circuit board
Author(s):
Fengguang Luo;
Mingcui Cao;
Xinjun Zhou;
Jun Xu;
Zhixiang Luo;
Jing Yuan;
Liangjia Zong;
Conghuei Zhang
Show Abstract
The configuration of polymer light waveguide electro-optical printed circuit board(EOPCB) is proposed in this paper. An
additional optical layer with light waveguide structure is used in conventional PCB to construct EOPCB. Light
waveguide core layer mould is made with SU-8 photolithograph. Polymer light waveguide layer which is embedded
between multiplayer PCB is made in experiment by Doctor-blading technology for large size application. Vertical cavity
surface emitting laser (VCSEL) array is used as optical transmitter array. PIN photodiode array is used as optical
receiver array. A MT-compatible direct coupling method is presented to couple light beam between optical
transmitter/receiver with light waveguide layer. The optical signals from a processor element chip on the PCB can
transmit to another processor element chip on the same PCB board through light waveguide interconnection in EOPCB.
So optical interconnection between chip to chip for parallel multiprocessor system can be reailzed by EOPCB.
Carbon-nanotube-based photonic devices
Author(s):
Shinji Yamashita
Show Abstract
We recently proposed and demonstrated a saturable absorber (SA) incorporating carbon nanotube (CNT). CNT-based
SA offers several key advantages such as: ultra-fast recovery time, polarization insensitivity, high optical damage
threshold, mechanical and environmental robustness, chemical stability, and the ability to operate at wide range of
wavelength bands. Using the CNT-based SA, we have realized femtosecond fiber pulsed lasers at various wavelengths,
as well as the very short-cavity fiber laser having high repetition rate. Besides the saturable absorption, CNT has been
shown to have high third-order nonlinearity, which is also attractive for realization of compact and integrated functional
photonic devices, such as all-optical switches and wavelength converters. In this paper, we first present photonic
properties of CNTs, and review our studies on CNT-based mode-locked fiber lasers. We also refer to fabrication
methods of CNT-based photonic devices. We show our recent research progresses on novel photonic devices using
evanescent coupling between optical field and CNT.
InAs/InP based quantum dot mode-locked semiconductor lasers at 1.5 um
Author(s):
Guang-Hua Duan;
F. Lelarge;
B. Dagens;
R. Brenot;
A. Accard;
A. Shen;
F. van Dijk;
D. Make;
O. Le Gouezigou;
L. Le Gouezigou;
J.-G. Provost;
F. Poingt;
J. Landreau;
O. Drisse;
E. Derouin;
B. Rousseau;
F. Pommereau
Show Abstract
This paper summarizes recent advances on InAs/InP mode-locked quantum dashes (QD) lasers, and their applications for
all-optical clock recovery, short pulse generation and millimeter wave generation. We demonstrate that QD FP lasers,
owing to the small confinement factor and the 3D quantification of electronic energy levels, exhibit a beating linewidth
as narrow as 15 kHz. Such an extremely narrow linewidth, compared to their QW or bulk counterparts, leads to the
excellent phase noise and time jitter characteristics when QD lasers are actively mode-locked. We report also on an
actively mode-locking tunnel injection quantum dash Fabry-Perot laser diode at 42.7GHz, generating nearly Fourier
transform limited pulses with a pulse width of 2ps over 16nm.
Influence of flux on the growth of InAs quantum dots on GaAs patterned substrate
Author(s):
Yuxin Song;
Zhongyuan Yu;
Yumin Liu
Show Abstract
Kinetic Monte Carlo simulations are applied on the investigation of the epitaxial growth of self-assembled InAs quantum
dots on GaAs substrate with periodic strain-relief patterns. The study is focused on the initial stage when the first
sub-monolayer is forming on top of the wetting layer. The flux is one of the most important growth parameters, which
are studied in detail. It is demonstrated that uniformly sized and regularly ordered island arrays can be obtained by
controlling flux, by means of analyzing the surface morphology, average island size, island size distribution and the
standard deviation of island size distribution. If interruption is introduced, the influence of flux will significant different.
The uniformity and order of islands will greatly affect the locating of quantum dots in sequent 3-D growth.
The strain energy density distribution of the capping layer surface for InAs/GaAs quantum dot along different growth directions
Author(s):
Zhongyuan Yu;
Yumin Liu
Show Abstract
In this paper, we calculated the strain distribution of low dimension structure using the elastic continuum model. The
strain energy density distribution on the different thickness of capping layer surface for the self-organized InAs/GaAs
quantum dots system is investigated by the numerical finite element method. The influence of the different growth
directions on the strain energy density distributions can be found from the calculated results. The results can explain
some experiment results, such as the ordering array of the quantum dots supper-lattices. So the growth direction and
spacing thickness can be regarded as another control parameters for strain engineering self-organized semiconductor
quantum materials. As a comparison, the strain distributions of other low-dimension self-organized materials are also
calculated.
Quantum-dot semiconductor waveguide devices
Author(s):
Z. G. Lu;
J. R. Liu;
S. Raymond;
P. J. Poole;
P. J. Barrios;
S. Haffouz;
D. Poitras;
G. Pakulski;
S. Taebi;
Y. Song;
X. P. Zhang;
T. Hall
Show Abstract
We have designed, fabricated and characterized self-assembled InAs/InGaAsP QD-waveguide devices around 1.55 μm.
In order to obtain optimal performance, we have investigated several QD-based semiconductor optical amplifiers
(SOAs) / lasers with different core geometry and doped profiles. To make the fair comparison between QD-SOA and
QW-SOA, InAs/InGaAsP QW-SOAs with the same structure and the doped profiles have been designed and
characterized. The experimental results indicate the QD-SOA is much better than QW-SOA in term of optical spectral
bandwidth, temperature sensitivity and output power stability. The
3-dB and 10-dB bandwidths of the amplified
spontaneous emission (ASE) spectra of the QD-SOA are 150 nm and 300 nm around 1520 nm. By using CW pump and
probe signals we have demonstrated a non-degenerated four-wave mixing (ND-FWM) process and the experimental
results indicate that the asymmetry of the FWM conversion efficiencies is eliminated by using the QD-SOA. To make
use of the inhomogeneous broadening which is one of the specific properties of QD waveguide devices, we have
designed and investigated the QD-based multi-wavelength semiconductor laser. A stable multi-wavelength laser output
with a 93-channel multi-wavelength laser with maximum channel intensity non-uniformity of 3-dB were demonstrated
on the basis of a single InAs/InGaAsP QD F-P cavity chip. All channels were ultra-stable because of the inhomogeneous
gain broadening due to statistically distributed sizes and geometries of self-assembled QDs.
The couple electronic state of the stack quantum dots by axial symmetrical finite element analysis
Author(s):
Yumin Liu;
Zhongyuan Yu;
Xiaomin Ren
Show Abstract
Semiconductor quantum dots have been of major interest in recent years. This has largely been simulated by progress
in quantum dot growth technology, whereby self-organized quantum dots array can be fabricated by MBE and MOCVD
facilities using Stranski Krastanow growth mode. Quantum does material has achieved broad applications in
optoelectronic devices and quantum information fields because of the unique 3D electron confinement. However, a good
understanding about the electronic, excitonic and optoelectronics properties of the quantum materials are very important
in fabrication nanostructure devices based on quantum dots. Based on the 1-band effective-mass theory, a finite element
numerical technique is developed to calculate the electronic structure of truncated conical shaped InAs GaAs vertical
aligned quantum dot molecular, including the wetting layer. Using the axis-symmetry model, the 3D effective-mass
Schrödinger equation with step potential barrier can be reduced to a 2D problem by separating variable technique, which
greatly reduced the calculation cost. Form the calculated results, we found that the coupling effects is obviously when the
separation distance is in the range of the less than 10nm. The wave functions will exhibits large probability in the region
between the quantum dots. In order to consider the effect of the distance between the two layers of quantum dots on the
electronic state coupling, we calculated the results when the distance is 6nm, 11nm, 14nm and 17nm. The ground state,
the second excited and the highest excited state will lower its energy with decreasing the distance between the quantum
dots, but the second excited state will increase its energy. With increasing the distance between the two quantum dots,
the coupling effect will become weaker, and for the ground state, the wave function distribution will tend to localized
only in one of the quantum dot, the energy become something degenerate. The calculated results show that the ground
state and the first excited state are degenerate. With decreasing of the distance, the degenerate states are broken, and the
energy levels are separated. In our simulations, the strain effects are ignored. In the future woks, strain should be taken in
to account as an easy way. The calculated results can help us to examine optoelectronic properties of the semiconductor
nanostructure based on multi sheet of quantum dots with wetting layers.
Determination on wave function of quantum structures using finite-difference time domain
Author(s):
Boyong Jia;
Zhongyuan Yu;
Yumin Liu
Show Abstract
With the interest in quantum structures, there is a need to have a flexible method that can help us to determine
eigenfunctions for these structures. In this article, we present a method that accomplishes this by using the simulation of
the Schrödinger equation based on finite-difference time-domain (FDTD). We choose one-and two-dimensional finite
square well potential, and one-and two-dimensional harmonic oscillator potential as examples. Giving the initial
condition, we determine the eigenfrequencies through a Fourier transform of the time domain data collected at the center
point in the problem space. Another simulation implements a discrete Fourier transform at the eigenfrequencies at every
point in the problem space, hence, the eigenfunctions can be constructed.
Resonant-cavity based monolithic white light-emitting diode
Author(s):
Lirong Huang;
Dexiu Huang;
Feng Wen
Show Abstract
We propose a new scheme of resonant-cavity (RC) based monolithic white LED, it relaxes the hard requirement of
high internal quantum efficiency of yellow multi-quantum (MQW) and offers an easy way to obtain high luminous
efficacy white light emission. In the proposed white LED, the blue MQW and yellow MQW active layer are embedded in
a resonant-cavity defined by the bottom distributed Bragg reflector(DBR) and top DBR. For a optimal design of
RC-based white LED, the extraction efficiency for yellow light is enhanced, while that for blue light is suppressed, thus
intensity ratio of yellow light in the emitting light is increased, which not only helps to obtain white emission in spite of
the low internal quantum efficiency of yellow light, but also doubles luminous efficacy. The color coordinates and
luminous flux of the emitting light from RC-based white LED are calculated and the performance dependence on
directionality is investigated.
High power vertical cavity surface-emitting laser with high reliability
Author(s):
Changling Yan;
Guoguang Lu;
Chunfeng He;
Li Qin
Show Abstract
High-power vertical-cavity surface-emitting lasers with InGaAs/GaAs quantum well active gain region
are investigated. By using AlAs oxidation technology, the devices have been fabricated in experiment, and the
characteristics of the device are carried out at room temperature. The 300μm-diameter VCSELs have the maximum
room temperature continuous wave (CW) optical output power of about 1.1W, and the threshold current of the device is
about 0.46A. The life test of the device is carried out in constant current mode. The life test of 300-μm diameter lasers
shows that the average lifetime is about 1800h at 80°C. The device degradation mechanism is also discussed in detail.
Characterization of white OLEDs
Author(s):
Wenbin Chen;
Lili Lu
Show Abstract
White OLEDs (WOLEDs) have attracted much attention for several applications, such as backlights in LCD, full-color
OLED display using on-chip color filters, and low cost illumination sources. OLEDs have typically very broad emissions,
which makes them uniquely suitable for light source applications. In this paper, some fundamentals of the CIE
colorimetry system including the color-rendering index are described. Given the spectral power distribution of WOLED,
the parameters of a light source (chromaticity coordinate, CCT, CRI, and the luminous efficacy) can be calculated. A
MATLAB program for this purpose is developed in this paper.
WOLEDs utilizing two primary-color emitters are fabricated. NPB doped with 2% Rubrene is used as the red-emitting
layer and anthracene derivative as the blue-emitting layer. With a structure of ITO/2TNATA(20nm)/NPB(20 nm)/
NPB:rubrene(2%)(10nm)/ anthracene (30 nm)/Alq3(20nm)LiF(1nm)/Al(100nm), a white light with CIE coordinates of
(0.34, 0.37) is generated. The color properties are presented in this paper. The results show that the white color can be
created from numerous combinations of different spectra. Based upon this, the characterization of the WOLED is
simulated and the design of WOLED for illumination is discussed.
In contrary to light source applications where illumination quality white is the most important, all colors are equally
important for display applications. The white spectrum of the two-emitter WOLED is transmitted through the typical red,
blue and green color filters. The performance of this color display is simulated and the WOLED design for display
application is discussed.
Parameter optimization of nonlinear SOA in an SOA-MZI packet-level self-synchronization scheme
Author(s):
Libo Cai;
Min Zhang;
Huining Han;
Wei Yang;
Peida Ye
Show Abstract
Introduced in this paper is an experimental system of packet-level self-synchronization using semiconductor optical
amplifier based Mach-Zehnder interferometer (SOA-MZI). The function of SOA-MZI in the system is analyzed, as well
as the relationship among key parameters of various components. A tunable optical delay line is used for the adjustment
of phase difference. It reveals that SOA-MZI is an effective way to extract self-synchronization clock in both
experiments and practical applications.
Fine-tuning of the spectral efficiency based on tunneling splitting in multiple quantum well system
Author(s):
Chongqing Huang;
Junqiang Sun;
Jing Liu;
Wenjing Hu
Show Abstract
Transmission studies for quantum well (QW) structures composed by two-dimension photonic crystals are presented. The results indicate that, with the multiple QW structure, each resonant peak which appears in the single QW structure would split, and the splitting times increases in step with the increasing number of the wells. It is also found that the frequency spacing between adjacent splitting spectra can be finely tuned by adjusting the barrier widths properly, leading to great improvement of spectral efficiency. The physical explanation of the origin of the spectral splitting are provided. These results provide the prospects in super dense wavelength division multiplexing for optical communication and precise optical measurement for the purpose of maximization of channel density.
Large aperture low threshold current 980nm VCSELs fabricated with pulsed anodic oxidation
Author(s):
Jinjiang Cui;
Yongqiang Ning;
Te Li;
Guangyu Liu;
Yan Zhang;
Biao Peng;
Yanfang Sun;
Lijun Wang
Show Abstract
Pulsed anodic oxidation technique, a new way of forming current blocking layers, was successfully used in
ridge-waveguide QW laser fabrication. We apply this method in 980nm VCSELs fabrication to form a high-quality
native oxide current blocking layer, which simplify the device process. A significant reduction of threshold current and a
distinguished device performance are achieved. The 500μm-diameter device has a current threshold as low as 0.48W.
The maximum CW operation output power at room temperature is 1.48W. The lateral divergence angle θparalleland vertical divergence angle θperpendicular are as low as 15.3° and 13.8° without side-lobes at a current of 6A.
Buffer optimization for high-quality InP-on-GaAs(001) quasi-substrates
Author(s):
Jing Zhou;
Xiaomin Ren;
Deping Xiong;
Jihe Lv;
Qi Wang;
Yongqing Huang;
Hui Huang;
Shiwei Cai
Show Abstract
In this work, we reported the buffers optimum of high-quality InP epilayer grown on GaAs substrate for fabrication of InP-related devices. First, LT-GaAs (450°C, 15nm)/LT-InP((450°C, 15nm) double LT buffers were deposited on the substrate as the initial layers. The effects of double LT buffers were studied compared with the results of single LT-InP buffer scheme. It was demonstrated that: (i) with a proper LT-GaAs buffer thickness, the double
LT-buffer became more "compliant" for strain accommodation than single LT-InP buffer; (ii) there existed an optimal thickness of
LT-GaAs buffer for a given thickness of LT-InP layer at which the crystal quality reached the best, just like the conventional buffer optimum process. Second, in order to block the "escaped" dislocations from the buffer/substrate interface, InxGa1-xP/InP (x≈0.2) strained superlattices (SLS) were introduced as defect filtering layers before the growth of the final InP layer. We investigated the effects of the periods and inserting position of the SLS on the stress relaxation and the crystal quality of InP top layer. It was suggested that when the total thickness of the epilayer was fixed, both the thickness and the periods and the distance from the interface should be carefully designed to reduce the stress and improve the crystal quality of the epilayer simultaneously. Finally, a 2-μm-thick InP epilayer was grown on GaAs substrate using (450°C, 15nm)/LT-InP(450°C, 15nm) double LT buffers combined with inserting 15-period (4nm/6nm) In0.8Ga0.2P/InP SLS into epilayer. Then X-ray diffraction measurements showed the best result of the full width at half maximum (FWHM) was 203 arcsec with estimated dislocation density of 2.8×107 cm-2.
Novel scheme to increase the operation speed of a SOA for all-optical wavelength conversion
Author(s):
Zhaoxi Wu;
Yuanqing Huang;
Zihua Weng;
Huangping Yan;
Yiju Wang;
Jin Wan;
Ruifang Ye
Show Abstract
All-optical wavelength converters (AOWCs) are considered to be important components in future wavelength-division-multiplexed
(WDM) networks. Cross gain modulation schemes in semiconductor optical amplifiers (SOA) are promising
candidates for an all-optical wavelength conversion application due to the simple implementation and effective
conversion. However, the slow gain recovery time of SOA limits the maximum operation speed and causes unwanted
pattern effects. This paper provides a novel scheme for wavelength conversion enables ultra-fast conversion speed. On
the one hand, we utilize a three-wavelength-device (TWD) to reduce the recovery time of the SOA. On the other hand,
we use an optical band pass filter (OBF) which central wavelength is blue shifted with respect to the central wavelength
of the probe beam to increase the frequency response. The combination of a reduction of the SOA recovery time and an
increase of the frequency response enables conversion speed potentially to achieve 160 Gb/s or even faster.
Novel optical modulator of silicon photonic crystals
Author(s):
Jiu-sheng Li;
Jian-rui Li
Show Abstract
We proposed a novel compact and integrated optical modulator, which consists of p-i-n silicon photonic crystals with
triangular lattice and a line defect waveguide. The device operation is based on a dynamic shift of the photonic band gap
(PBG), which is induced change in the silicon refractive index by the free carrier injection. We have numerically
analyzed and investigated its light modulation performance by using the finite-difference time-domain method. Being a
small size and high performance, the designed optical modulator can be used in photonic integrated circuits.
Structural and optical properties of InGaN/GaN multiple quantum wells structure for ultraviolet emission
Author(s):
Baozhu Wang;
Xiaoliang Wang;
Huanming Wen;
Ruihong Wu;
Guoxin Hu;
Junxue Ran;
Hongling Xiao
Show Abstract
InGaN/GaN multiple quantum wells (MQWs) structure for ultraviolet emission has been grown on sapphire by
metalorganic chemical vapor deposition (MOCVD). The High resolution x-ray diffraction (HRXRD), atomic-force
microscopy (AFM) and photoluminescence (PL) are used to characterize the structural and optical prosperities of
MQWs, respectively. HRXRD shows multiple satellite peaks to 3rd order indicates the high quality of InGaN/GaN layer
interface. AFM measurement shows that there are some spiral growth hillocks and 3D nanostructures on the MQWs
surface. They are related with the surface kinetics or thermodynamics of InGaN growth. Temperature-dependent PL
results show that there exists a clear excition-localization effect in the InGaN/GaN MQWs. The fitted σvalue of
InGaN/GaN MQWs is around 8meV. The emission peak was almost unchanged with the increase PL excitation power.
Those results indicate there is almost none piezoelectric field-induced quantum-confined stark effect in the InGaN/GaN
MQWs due to the low In content and thin quantum well thickness.
Theory study of AlInGaN quantum well with different barriers
Author(s):
Feng Wen;
Deming Liu;
Lirong Huang
Show Abstract
We investigate the optical gain properties of InGaN quantum well with different symmetry barriers and asymmetry
barriers based on a self-consistent calculation which solves the Schrodinger equations and Poisson equations
simultaneously. It is found that the AlxInyGa1-x-yN barriers which can eliminate the internal polarized field by adjusting
the component x and y can improve the emission intensity in a large extent compared with other barriers. The internal
polarized field is an important but not the only one factor to affect the emission power, the barrier confinement, the
energy band are all have to be taken into considered. Otherwise, a quantum well which has proper asymmetry barriers
also can obtain better emission efficiency than the well with symmetry barriers.
Picosecond pulse Raman amplification and controlled time delay in silicon-on-insulator waveguides
Author(s):
Jianwei Wu;
Fengguang Luo;
Mingcui Cao;
Qingtang Zhang;
Yongjung Huang
Show Abstract
The stimulated Raman amplification of picosecond Stokes pulse is numerically investigated in ultra-small
silicon-on-insulator optical waveguide. Numerical results show that we obtain the gain of up to 30-dB for weak Stokes
pulse in the co-propagation configuration for 10-mm-longth waveguide using high intensity pump optical pulse. The
peak gain, pulse width, rise time, and fall time of Stokes pulse will experience the variation course of decaying then
increasing with increasing waveguide length. The time delay of output Stokes pulse is controlled by adjusting the initial
time delay of both pump and Stokes pulses.
Research of photodetector and its array in standard CMOS technology
Author(s):
Jiantao Bian;
Xiang Cheng;
Chao Chen
Show Abstract
Silicon photodetector is easy to be integrated with all kinds of Silicon IC to get monolithically OEIC. And the
photodetector array is also widely applied. A kind of
CMOS-process-compatible N+/N-Well/P-Sub photodetector and its
array are analyzed in this paper. Depended on the basic
time-dependent equations of photodetctor and analyzed by
Laplace transform method, the intrinsic frequency response characteristic is numerically calculated. The effect of reverse
bias voltage on spectral responsivity is also discussed. The photodetector is fabricated in 0.5μm CMOS process. At
780nm wavelength incident light, the measured and calculated responsivity are 0.253A/W and 0.251A/W, respectively.
The variety of measured responsivity with bias voltage is about 1.8mA/(W•V). At a reverse voltage of 5V, the maximum
dark current is 0.148nA. And the junction capacitance and -3dB frequency are also measured. The crosstalk factor of
photodetector with PN junction isolation and 5μm isolated space in CMOS technology is less than 5%.
Single-SOA-based all-optical XNOR and AND gates
Author(s):
Pei-li Li;
De-xiu Huang;
Xin-liang Zhang;
Guang-xi Zhu
Show Abstract
Semiconductor optical amplifier (SOA)-based all-optical XNOR and AND gates using four-wave mixing (FWM) and
cross-gain modulation (XGM) with improved dynamics are simultaneously realized. The effects of the input optical
wave powers and injection current on the critical factors of the logic gate performances, such as the ON-OFF contrast
ratio, the output power level of the logic "1", and the output power difference of the logic "1", are theoretically
investigated in detail. In addition, the effect of the
counter-propagating CW pump on the gain recovery is analyzed.
Luminescence properties of Cu and Cu,Al doped ZnS quantum dots
Author(s):
Xiaosong Zhang;
Lan Li;
Xiaoyi Dong;
Guiyun Kai;
Dongqing Dong;
Yanfang Zhang;
Jiangyong Li
Show Abstract
Free-standing ZnS:Cu and ZnS:Cu,Al quantum dots were prepared in the aqueous medium from readily available
precursors. The construction, morphology and luminescence properties of the ZnS:Cu and ZnS:Cu,Al quantum dots were
evaluated by XRD,TEM and photoluminescence spectra. The average particle size was calculated using the Scherrer
formula to be 5nm, which is also observed from HRTEM image. In PL spectra, 0.7% Cu and 0.4% Cu -doped ZnS:Cu
quantum dots have emission peak around 470 nm and 500 nm, which attributed to the transition from the shallow donor
level (sulfur vacancy) to the e level and t2 level of Cu2+ respectively. And PL spectra of ZnS:Cu,Al quantum dots is
similar with the PL of ZnS:Cu quantum dots, but the luminescence intensity of quantum dots ZnS:Cu,Al increase, which
arise from that Al 3+ ions as co-activated enhance donor level.
NIR luminescence properties of ZnS:Er,Yb quantum dots
Author(s):
Xiaosong Zhang;
Xiaoyi Dong;
Lan Li;
Zhi Wang;
Yange Liu;
Dongqing Dong;
Yanfang Zhang;
Guiyun Kai
Show Abstract
Free-standing ZnS:Er and ZnS:Er,Yb quantum dots were prepared in the aqueous medium from readily available
precursors. The construction, morphology and luminescence properties of the ZnS:Er and ZnS:Er,Yb quantum dots were
evaluated by XRD,TEM and photoluminescence spectra. The average particle size was calculated using the Scherrer
formula to be 4nm, which is also observed from HRTEM image. The spectra of ZnS:Er and ZnS:Er,Yb quantum dots
have broad emission between 1450 nm and 1650 nm centered at 1575 nm with the excitation wavelength 980 nm, which
can be attributed to the 4I13/2→4I15/2 transition. But the intensity of ZnS:Er,Yb quantum dots significantly increases with
the addition of Yb as a sensitizing ion into ZnS:Er quantum dots. Because that Yb3+ absorbed the energy and transfer
energy from the 5F5/2 level of the 4I11/2 level (Er3+ ) and improve population accumulation on the 4I11/2 level.
Two-dimensional photonic crystal polarizer modulated by silicon resin
Author(s):
Chunhua Tan;
Xuguang Huang
Show Abstract
Photonic crystals(PCs)have many potential applications because of their ability to control light-wave propagation. In
this paper, we theoretically investigate the tunability of light propagation in photonic crystal waveguides in
two-dimensional photonic crystals with square lattices composed of heat-resistant silicon resin. Waveguides can be
obtained by the infiltration of silicon resin into air regions in two-dimensional photonic crystals composed of air holes
with square lattices of dielectric cylinders. The refractive index of silicon resin can be changed by manipulating the
temperature of the sample. Numerical simulation by solving Maxwell's equations using the plane wave expansion(PWE)
method shows that the band gaps can be continuously tuned by silicon resin, accordingly the light propagation in
photonic crystal waveguides can be controlled. The band gap is analyzed in the temperature range of 20°C-120°C. In our
work, the gap map for a square lattice of dielectric cylinders is also simulated. The method can separate TM- and
TE-polarized modes in the waveguide. Such a mechanism of band gap adjustment should open up a new application for
designing field-sensitive polarizer in photonic integrated circuits.
Simulation and analysis of gain-transparent SOA used as optical phase-modulator in DPSK applications
Author(s):
Wei Hong;
Dexiu Huang;
Xinliang Zhang;
Guangxi Zhu
Show Abstract
Gain-transparent semiconductor optical amplifier (GT-SOA) can be used as optical phase-modulators in
Mach-zehnder interferometer configuration for 2R or 3R regeneration, wavelength conversion of differential phase
modulated signals and all-optical format conversion from on-off keying (OOK) to binary phase shift keying (BPSK).
Numerical simulation of the phase modulation effect of GT-SOA is performed using a wideband dynamic model and the
performance is evaluated using the differential-phase-Q factor. Performance improvement by holding light injection is
analyzed and non-return-to-zero (NRZ) and return-to-zero (RZ) modulation formats of the OOK signal are considered.
Finite element method analysis of LiNbO3 fiber type modulator
Author(s):
Jiu-sheng Li;
Jian-rui Li
Show Abstract
A novel fiber type traveling-wave modulator is developed. The finite element method (FEM) has been used to analyze
the performance of the proposed modulator with coplanar waveguide (CPW) electrode structures. The optimized
structures of the traveling-wave modulator are obtained. The results show that the novel modulator has a 3dB optical
bandwidth of 112GHz, a half driving voltage of 2.7V, and characteristic impedance of 51.2Ω at 1.55μm wavelength.
Noise-reduction of experimental optical chaos and its attributes
Author(s):
Zhiwei Zhu;
Yichao Meng;
Nian Fang;
Zhaoming Huang
Show Abstract
A time series of experimental optical chaos signal with dynamic equation unknown and low SNR is obtained. The
wavelet multi-resolution decomposition algorithm is applied here to reduce the noise mixed in the experimental optical
chaos signal. The performance of the algorithm is verified by Lorenz chaos signal mixed with noise, which shows that
the SNR is increased by 10dB or so. Some parameters of the optical chaos attributes are calculated before and after
noise-reduction. It shows that the noise-reduction algorithm can improve the precision of the Lyapunov exponent
calculated with small data method, and a completely opposite wrong result can be avoided by the noise-reduction process
when computing the minimum embedding dimension with Cao method. The small data sets method is improved by Cao
method (minimum embedding dimension) and mutual information method (delay time). As the result is shown, the error
of the largest Lyapunov exponent is reduced by nearly 30%, and the largest Lyapunov exponent of the optical chaos
signal is 0.3896 obtained with this method.
Modeling of dynamics of DBR tunable lasers based on transfer matrix method
Author(s):
Shi Kai;
Yonglin Yu
Show Abstract
The static Transfer Matrix Method (TMM) and Multi-mode Rate Equations (MMRE) are combined together to simulate
dynamic characteristics of three section DBR lasers. Dynamic Side Mode Suppression (SMSR) is introduced to study
wavelength switching transients for the first time, along with the lasing spectrum characteristics.
The spectrum of chaos signal based on Wigner distribution
Author(s):
Xiaodan Guo;
Nian Fang;
Zhaoming Huang
Show Abstract
An improved method of distinguishing chaotic signal based on Wigner distribution (WD) is presented. Except for the
width of spectrum, the peak values speciality of time-frequency in 3-dimensional figure is employed to distinguish
chaotic signal. The method is verified by Lorenz system. The Wigner distribution of the chaotic signal is compared with
that of the gauss noise, and the result dedicated that the spectrums of them can be distinguished. The Wigner distribution
is used to dispose the chaotic signal of the fiber ring laser base on Semiconductor Optical Amplifier (SOA) too, and the
result is consistent with that of Lorenz system. In the conclusion, 3-dimensional WD distribution could more accurately
show chaos spectrum characteristic and could be an effective method for distinguishing the chaos and other signals.
Activation experiments and quantum efficiency theory on gradient-doping NEA GaAs photocathodes
Author(s):
Jijun Zou;
Zhi Yang;
Jianliang Qiao;
Pin Gao;
Benkang Chang
Show Abstract
Two gradient-doping GaAs photocathodes were designed and activated, the achieved highest integral sensitivity for the
gradient-doping cathode is 2178μA/lm, which is much higher than that of uniform-doping cathode. The increase in the
integral sensitivity is attributed to the electric field induced in the active layer of gradient-doping cathode. We analyze
the transported mechanism of gradient-doping cathodes and solve the quantum efficiency equations of exponential-doping
cathode, which is a special gradient-doping cathode with a constant induced electric field, from the one-dimensional
continuity equations. According to these equations, we calculate the theoretical quantum yield of the
exponential-doping cathodes, and compare the performance of exponential-doping cathodes with that of uniform-doping
cathodes. The theoretical results show that the exponential-doping structure can increase the quantum yield of
photocathodes evidently, for the transmission-mode cathodes the increase is even more pronounced.
Design of high performance DBR lasers for WDM fiber optic communications
Author(s):
H. H. Yee;
C. L. Xiao;
C K. Liao;
H. Y. Tung;
H. H. Lu
Show Abstract
Four-section sampled-grating DBR (SGDBR) lasers, including two sampled grating DBRs, gain and phase tuning
sections, were designed by a InGaAlAs / InP strained multiple quantum well microstructure. The lengths of gain and
phase sections are 280 μm and 150 μm, respectively. One SGDBR, accommodating 10 sample periods with a total length
of 270 μm, is situated adjacent to the gain, and another SGDBR, containing 11 sample periods with a total length of 330
μm, is to the right of phase section.
The estimated threshold current and characteristic temperature, T0 , were 10 mA and 166 °K respectively. High
T0 reflects excellent electron confinement of the MQW structure. The optical coupling strength and the cavity-mode
spacing of DBR lasers were carefully chosen. With appropriate tuning mechanisms, the tunable SGDBR lasers produced
172 transmission channels, each with side-mode suppression ratios higher than 40 dB. Under 100 mA current driving, the
lasers could be operated with a bandwidth of 20 GHz and the channel switching could be completed within 1 nS.
Moreover, from the observations on the relative intensity noises as well as on the eye diagram, the lasers do exhibit
excellent dynamic characteristics.
Simulation of integrated DFB lasers in serial in a convenient model with transfer matrices method
Author(s):
Hongyun Xie;
Yang Wang;
Wei Zhang;
Lijian He;
Yongping Sha;
Wangrong Zhang
Show Abstract
For device analysis and optimization, a model based on Transfer Matrices Method was built to simulation the
performance of a new integrated device. This novel DFB laser was composed of two serial sections to provide selectable
wavelengths. The periods of two Bragg gratings were different and were chosen to achieve a spacing of 20nm between
the two corresponding Bragg wavelengths. The model is more simple and convenient to simulate optical integrated
device than other direct simulation methods used before. The simulation results prove that this novel waveguide structure
of the serial DFB lasers is feasible. The integrated optical device was fabricated and two wavelengths of 1.51um and
1.53um were realized under different work conditions.
Design of preamplifier for PIN/ HBT OEIC optical receiver
Author(s):
Qiang Wu;
Yong-Qing Huang;
Hui Huang;
Hai Lin Cui;
Yi Qun Li;
Ang Miao;
Xiao-Min Ren
Show Abstract
Optical receiver of high speed and high sensitivity is indispensable for long distance fiber-optic communication systems
of transmitting rate up to Gb/s. In recent years, OEIC (Optoelectronic Integrated Circuits) optical receiver has attracted
more and more attention for its advantages over conventional optical receiver such as minimized parasitics, lower cost,
higher reliability and compact size. In this paper, design of preamplifier for InP-based PIN/HBT OEIC optical receiver
with share layer structure was presented. As a basis for design of preamplifier, HBT large signal model (GP model)
was investigated and model parameters were extracted and optimized. The extracted GP model shows a good agreement
with measured characteristics of HBT fabricated. Based on this GP model, the preamplifier was designed and fabricated
which exhibits good high-frequency characteristics of −3dB bandwidth is up to 2.0 GHz.
Tunable ultraviolet laser source from a frequency doubled Alexandrite laser
Author(s):
Shuhang Liu;
Jingjiao Liu;
Lijun Wang
Show Abstract
A tunable ultraviolet laser source in the spectrum range of 0.36-0.388 μm was obtained as second harmonics from a
frequency doubled Alexandrite laser whose output covers the wave range over 0.72-0.78 μm. A LBO crystal was used as
frequency doubling crystal. The phase mateching angle in the wide spectrum range of the crystal was calculated, and the
crystal was cut in the way that the normal incidence at the center wavelength of the fundamental wave at the crystal. The
output spectrum line was measured and the highest second harmonics conversion efficiency reached 1.2% from long
pulse fundamental wave at the center wavelength.
The role of dispersive magnetic permeability in ultrashort electromagnetic pulse propagation in nonlinear metamaterials
Author(s):
Shuangchun Wen;
Qiang Lv;
Xi Cheng;
Leyong Jiang;
Wenhua Su
Show Abstract
Compared to the non-magnetic ordinary dielectrics, the
negative-index metamaterials have not only a dispersive electric
permittivity but also a dispersive magnetic permeability. The purpose of this paper is to identify the role of dispersive
magnetic permeability in nonlinear propagation of ultrashort electromagnetic pulses in metamaterials. Firstly, we derived
a generalized system of coupled three-dimensional nonlinear Schroedinger equations suitable for few-cycle pulse
propagation in the metamaterial with both nonlinear electric polarization and nonlinear magnetization, which clearly
demonstrates the role of dispersive permeability in nonlinear pulse propagation: In the linear propagation aspect, its
contribution is buried in the ordinary dispersive terms; while in the nonlinear propagation aspect, the dispersive
permeability manifests itself as a nonlinear polarization dispersion, although it is a linear parameter. Secondly, by
exemplificatively using the coupled nonlinear Schroedinger equations in the Drude dispersive model, we quantitatively
discussed the influence of dispersive permeability on pulse propagation in metamaterials.
All-optical ultrawideband monocycle and doublet generation using cascaded PPLN waveguides
Author(s):
Jian Wang;
Junqiang Sun;
Qizhen Sun
Show Abstract
Ultrawideband (UWB) is an attractive technology for short-range
high-capacity wireless communication systems. A
novel all-optical method for generating UWB pulses is proposed and theoretically analyzed using cascaded periodically
poled LiNbO3 (PPLN) waveguides. The operation principle relies on the sum-frequency generation (SFG) in the first
PPLN and the cascaded second-harmonic generation and difference-frequency generation (SHG+DFG) in the second
PPLN. We simulate the proposed PPLN-based UWB pulses generation using the well-known coupled-mode equations
describing the SFG and SHG+DFG processes. A pair of
polarity-reversed UWB monocycle pulses is generated with a
central frequency of 5 GHz and a 10 dB bandwidth of 8.75 GHz. Thus the fractional bandwidth is 175%. Moreover, a
pair of polarity-reversed UWB doublet pulses is also obtained. One has a central frequency of 5 GHz, a 10 dB bandwidth
of 7.5 GHz, and a fractional bandwidth of 150%, and the other has a central frequency of 5 GHz, a 10 dB bandwidth of
3.75 GHz, and a fractional bandwidth of 75%. It is found that all generated pairs of polarity-reversed UWB monocycle
and doublet pulses match well with the UWB definition of Federal Communications Commission (FCC).
Analysis and measurement of thermal-electrical performance of microbolometer detector
Author(s):
Lianjun Sun;
Benkang Chang;
Junju Zhang;
Yafeng Qiu;
Yunsheng Qian;
Si Tian
Show Abstract
Microbolometer detector is very competent as uncooled infrared detector for a wide range of thermal imaging
applications, since it has been found to be more sensitive and has the advantage of using standard Si micro-fabrication
process compared with pyroelectric or ferroelectric technology. The heart of microbolometer detector is a two
dimensional array of thermal sensitive thin-film layers, which can change their temperatures and resistivities depending
on the radiation absorbed. During the entire thermal imaging process, the microbolometer detector's substrate
temperature, calibration temperature and ambient temperature are the key parameters which determine the thermal-electrical
performance and the ultimate imaging quality of the microbolometer detector. In this work, based on the
analysis of the characteristics of these parameters, the experiment has been conducted with the uncooled infrared thermal
imaging system based on 320×240 amorphous silicon microbolometer detector working at different substrate
temperatures, adopting different calibration temperatures for different ambient temperatures. The corresponding
measurement results of the system's NETD, residual nonuniformity and power consumption, as well as the system's
imaging results are presented, which all have a great agreement of the theory analysis above.
Structural and photoluminescence properties of porous silicon with r.f.-sputtered thin films
Author(s):
Yujuan Zhang;
Zhenhong Jia
Show Abstract
Thin Sn films in the thickness range 0.3-2nm are deposited by
r.f.-sputtering on porous silicon (PS) anodized
on p-type silicon. Microstructural features of the samples before and after r.f.-tin-sputtered are investigated with scanning
electron microscopy (SEM). The photoluminescence (PL) studies showed that a broad luminescence peak of PS near the
621nm region gets a reduction in intensity, and a new peak at 441nm was produced at first and then disappeared. The
FTIR spectra on the PS/Sn structure revealed no major change of the native PS peaks.
The cavity enhancing effect of F-P cavity mode on the non-degenerated four-wave mixing in distributed-feedback semiconductor laser diodes
Author(s):
Jiagui Wu;
Guangqiong Xia;
Xinhong Jia;
Xiaojuan Yan;
Jun Li;
Xiaofa Wang;
Zhengmao Wu
Show Abstract
All-optical wavelength conversion based on four-wave mixing (FWM) is one of the key techniques for building
dynamic optical networks. In this paper, the cavity enhancing effect of the residual F-P cavity mode on the
non-degenerated four-wave mixing (NDFWM) in a distributed-feedback semiconductor laser diode (DFB-LD) have
been investigated both experimentally and theoretically. The conversion efficiency of NDFWM is obtained at small or
large frequency detuning range. The results show that the NDFWM can be enhanced obviously when the probe
wavelength matches one of the F-P cavity modes, and the high conversion efficiency can be achieved even if the
frequency detuning between the injection probe frequency and free-running frequency of the DFB-LD is up to THz.
Linear frequency modulation with electronic-optics modulator
Author(s):
Changqing Cao;
Xiaodong Zeng;
Yili Zheng;
Huanhuan Liu;
Xiaoyan Zhao
Show Abstract
The spatial resolution of a space communication system is constrained by the diffraction limit of the telescope aperture.
In a frequency-modulated continuous wave (FMCW), the frequency of the laser is ramped, and the frequency difference
between the reflected wave and a local-oscillator wave is monitored. For maximum performance the frequency ramping
should be linear. Linear frequency modulation (LFM) of the laser emission is a commonly used method for improving
the detection sensitivity. Because of the available technology, techniques that use relatively low modulation frequencies
were implemented first. In the early 1980's, an elegant measurement method based on frequency modulation opened up
new applications for spectroscopy with spectrally modulated laser light. In this paper we analyzed systematically the
principles of saw tooth-wave optical FMCW. For optical FMCW, because all the practical optical waves are from single-mode
lasers, and because the laser beam from a single-mode laser is coherent in space due to the nature of stimulated
emission, the spatial coherence is always satisfied, and therefore only temporal coherence need be considered. The chip
signal, experimental system, and results are analyzed and discussed.
Study on the collimation of laser diode beams
Author(s):
Yili Zheng;
Xiaodong Zeng;
Changqing Cao;
Zhejun Feng
Show Abstract
Laser Diodes (LDs) are becoming increasingly attractive as small and reliable laser-beam sources,
with applications that include pumping of solid-state lasers, materials processing, and medicine. However,
because of the poor beam quality of its output beam, which affects its direct applications, thus people pay
much attention on how to shape the beam of the high power laser diode bar effectively. In this paper some
typical beam shaping methods, shaping principles, key techniques and shaping effects are discussed. Based on
geometric optical analysis, the collimation properties of the off-axis light wave through a cylindrical lens and
elliptical cylindrical lens are separately analyzed in detail by rays tracing formulas, the collimation effects of
them are also made a comparison.
Focused light from a metallic nanostructure composed by a nanoparticle and a nanoslit
Author(s):
Guo-ting Zhang;
Juan Liu;
Chuan-fei Hu;
Fang Sun;
Xiao-xing Su
Show Abstract
We investigate the focused light from a metallic nanostructure by the coupling of a metallic nanoparticle and a metallic
nanoslit flanked with periodic sinusoidal grating on one surface. We employ the boundary element method (BEM) to
simulate the optical field distribution and the transmission resonant spectrum. The numerical results show that focused
light are formed from the metallic nanoslit system. Such device can be used for miniature optical antennas in the optical
regime, which can transmit or receive light along a specific direction for a given wavelength. Potential applications
include that the coupling light in or out of fibers and the achieving the miniature optical source.
Numerical investigation of differential phase noise and its power penalty for optical amplification using semiconductor optical amplifiers in DPSK applications
Author(s):
Wei Hong;
Dexiu Huang;
Xinliang Zhang;
Guangxi Zhu
Show Abstract
A thorough simulation and evaluation of phase noise for optical amplification using semiconductor optical
amplifier (SOA) is very important for predicting its performance in differential phase shift keyed (DPSK) applications.
In this paper, standard deviation and probability distribution of differential phase noise are obtained from the statistics of
simulated differential phase noise. By using a full-wave model of SOA, the noise performance in the entire operation
range can be investigated. It is shown that nonlinear phase noise substantially contributes to the total phase noise in case
of a noisy signal amplified by a saturated SOA and the nonlinear contribution is larger with shorter SOA carrier lifetime.
Power penalty due to differential phase noise is evaluated using a semi-analytical probability density function (PDF) of
receiver noise. Obvious increase of power penalty at high signal input powers can be found for low input OSNR, which
is due to both the large nonlinear differential phase noise and the dependence of BER vs. receiving power curvature on differential phase noise standard deviation.
On-line measurement system of GaAs photocathodes and its applications
Author(s):
Jijun Zou;
Lin Feng;
Gangyong Lin;
Yuntao Rao;
Zhi Yang;
Yunsheng Qian;
Benkang Chang
Show Abstract
The preparation process of GaAs photocathodes is very complicated, in order to prepare the high performance cathodes,
it is crucial to obtain information enough to evaluate the preparation process in real time. Based on a particular transfer
light setup and a flexible communication network, we develop an
on-line measurement system for GaAs cathode
preparation, which is used to measure the pressure of activation chamber, sample temperature, photocurrent, spectral
response curves, and currents heating Cs and oxygen dispensers during the heat-cleaning or activation processes of
cathodes. According to these signals, we present some simple and real-time evaluation techniques for cathode
preparation. Several peaks of pressure are observed in the pressure variations measured during heat cleaning. These
peaks corresponding to the desorption of AsO, As2O3, Ga2O and Ga2O3 from the sample surface at different
temperatures, respectively, are used to evaluate the effect of heat cleaning very well, while the signals measured during
activation can be used to analyze and optimize the activation technique. Based on a revised quantum efficiency equation,
many performance parameters of cathodes are obtained from the fitting of spectral response curves. According to these
parameters, the performance of cathode material and the effect of activation can be evaluated.