Optoelectronic devices toward monolithic integration
Author(s):
V. Ghergia
Show Abstract
Starting from the present state of tl art of discrete devices up to the on going realization of monolithic semicorxtuctor integrated prototypes an overview ofoptoelectronic devices for telecom applications is given inchiding a short classification of the different kind of integrated devices. On the future perspective of IBCN distribution network some economica of hybrid and monolithic forms of integration are attempted. lnaflyashoitpresentationoftheactivitiesperformedintbefieldofmonolithic integration by EEC ESPR1T and RACE projects is reported. 1.
Mesoscopic structure for optoelectronics
Author(s):
Tatsuya Kimura;
Hiroaki Ando
Show Abstract
Recent advances in semiconductor crystal growth and process techniques have made it possible to produce semiconductor wire and box structures on a mesoscopic scale (''''1Onm). The interference of electron waves in the mesoecopic structures bring about various phenomena which are interesting from the view points of solid-state physics as well M device application. This paper addresses the recent progress in research on the semiconductor rnesoscopic structures that is fabrication processes characterization and application to optical devices. The unique optical features of the mesoscopic structures are discussed in relation to the quantum coithnenient effects in one-dimensional quantum wires and zero-dimensional quantum boxes. The carrier confinement effects in the low-dimensional systems lead to new concepts for device physics which utilize nonlinear birefringence and coherent nonlinearity. The current status and the problems associated with the fabrication of these semiconductor low-dimensional structures are also discussed. I.
Electric field effect in GaInAs/InP quantum wire and quantum box structures and application to intersectional optical switch
Author(s):
K. G. Ravikumar;
Takuya Aizawa;
Masahiro Asada;
Yasuharu Suematsu
Show Abstract
Large electric field induced refractive index variation and large index variation absorption loss variation ratio in low fundamental absorption region are theoretically reported in a GaInAs/InP quantum box (QB) structure. This effect is shown to be applicable to low loss intersectional type optical switch. Moreover the Q B size dependence as well as fluctuations in QB size on QB-intersectional type optical switch was also discussed. As a first step towards the realization of such high-dimensional structure we have fabricated and measured the index variation in a GaInAs/InP multi-layered ( 3layers) quantum wire structure. The measured index variation was around 4 at an applied reverse bias voltage of 3V. I.
Polarization selective electro-optic effect in coupled quantum-wire arrays
Author(s):
David S. Citrin;
Yia-Chung Chang
Show Abstract
We investigate the electro-optic effect in quantumwire (QWR) arrays and discuss possible applications for self-electro-optic-effect devices. By application of a static electric field normal to the growth planes the interband optical selection rules are modulated between one and two dimensional due to heavy-holelight-hole mixing. I.
Noise considerations in the design of long haul lightwave communication systems
Author(s):
Renuka P. Jindal
Show Abstract
Magnitude of the signal relative to noise determines the ultimate quality of all information transmission. In a lightwave system there are several fundamental and nonfundamental noise mechanisms that govern the system ormance. In this paper concepts related to these issues will be developed and a review of the current status of this rapidly evolvmg field will be given. 1.
Component video signal-to-noise ratio analysis of optical fiber video transmission systems
Author(s):
B. Selvan;
Roger J. Green
Show Abstract
The objective of this paper is to investigate the theoretical aspects of colorimetric noise analysis of component video signals for an optical fibre video transmission systems. The design of a low noise optical fibre colour video transmission system requires information regarding the degradation of various hues or at least the colours to which the eye is more sensitive in the presence of system noise. An expression for objective component video signal-to-noise ratio called the Display Signal-to-Noise Ratio (DSNR) is derived for both subcarrier frequency and amplitude modulated systems for the first time. The DSNR expression take into account the effects television receiver decoding and the nonlinearity of the display tube. A fundamental relationship between the input composite video SNR and the DSNR is established. Using this analysis impairments in various hues at different saturations and at different luminances are examined. The effect of the input noise spectrum on displayed primary colours is also analysed. The analysis discussed here is shown to be useful not only for present but also for future video systems and for dynamic noise reduction applications. 337 L
Temperature invariance of quantum well modulators using a feedback circuit based on quantum confined stark effect
Author(s):
Dipankar Biswas;
Pallab Bhattacharya;
Jasprit Singh
Show Abstract
The design and performance of a novel circuit working with a Gallium Arsenide multiquantum well p-i-n modulator is reported. The circuit can rapidly compensate for the temperature dependent shift of the excitonic energy position of quantum confined stark effect modulators. The energy position remains invariant over a temperature of 10K. The circuit is simple and can be operated with a single device or an array of modulators. I .
Generation of sub-Poisson distribution of light
Author(s):
P. S. Ramanujam;
N. Gronbech-Jensen
Show Abstract
We describe a modification of a nonlinear
Mach-Zehnder interferorneter to produce
a sub-Poissonian photon distribution and
an experimental set-up to realize it.
It is shown that it is possible to achieve
a substantial reduction in the photon
number uncertainty with a high power
efficiency.
Acoustic-optic techniques for phased-array antenna processing
Author(s):
Nabeel Agha Riza
Show Abstract
An acousto-optic phased array antenna beamformer with independent phase and carrier control capability is experimentally demonstrated using single-sideband signals driving two acousto-optic devices. A dynamic range of 66. 6 dB +2 MHz and carrier-to-noise of 126. 9 dBIHz +2 MHz is measured. This beamformer has wide antenna tunable bandwidth and intrapulse beamforming capabilities. L
Growth and characterization of high quality strained GaAs Epitaxial Layers
Author(s):
S. Dhar;
Kanad Mallik
Show Abstract
Iritum arxi antincny-dcped strain layers
of GaAs grcn by liquid phase epitaxy are
st3.ted hy phcal, electrical and cçtical
techniques . Doping ranges to obtain lci
dislocaticri dsity GaAs are assessed. Nz
deep levels associat1 with irx1izn arx
antinony dopants are identified by
photocurrent technique, and their possible
origins are discussed.
Nanocomposite sol-gel route to low K ceramic substrates
Author(s):
Sridhar Komarneni;
Lalba Rani
Show Abstract
Aluminosilicate gels of different alumina and silica ratios and cordierite MgAkSi5O1 gels were made by the nanocomposite sol-gel route and sintered to obtain highly dense materials. Measurements of the dielectric constant K and dissipation (loss) as a function of temperature and frequency showed that low dielectric constants of 5. 6 and 5. 4 at 1 and 4 MHz respectively for cordierite and of 6. 9 and 6. 7 at 1 and 4 MHz respectively for mullite at 25C were achieved. Aluminosilicate materials prepared with 10 wt A12O and 90 wt SiO showed the lowest dielectric constants of 4. 27 and 4. 20 at 1 and 4 MHz respectively.
Semiconductor laser amplifier and its optoelectronic properties for application in lightwave communication systems
Author(s):
V. V. Luc;
Petr Georgievich Eliseev;
M. A. Man'ko;
M. V. Tsotsoriya
Show Abstract
Output power and fiber-to-fiber gain along with infernal gain of the active element and optoelectronic signal curves at different values of input power versus pumping current are measured for the amplifier modules on the base of AR-coated InGaAsP/InP BH diodes. It is shown that diagnostics of the amplifier module oper''ation regime may be performed by voltage measurements and the optoelectronic signal can be used to monitor optical information passage in the regenerator device or for the distributed access the data transmitted in the lightwave comrnunicat ion systems. I.
Photoluminescence on InP: effect of surfaces and interfaces
Author(s):
T. K. Paul;
D. N. Bose
Show Abstract
It has been shown that improved surface properties of InP could be achieved through HF and sulfide NaS. 9HO) treatments. The photoluminescence (PL) intensity was found to increase due to reduction in interface state density after chemical treatments. X-ray photo-electron spectroscopy (XPS) studies revealed that the formation of IflF3 and P2S3 after HF and sulfide treatment respectively are responsible for better interfacial behaviour. I.
LPE growth of InP and InGaAs and applications in fibre optics
Author(s):
D. N. Bose;
Arvind Kumar
Show Abstract
Liquid phase epitaxy (LPE)
is a very suitable growth technique for
InGaAs detectors. The growth of high
purity epitaxial layez wth low
electron concentrationl0 cm however
requires prolonged baking to reduce
background impurity concentrations. This
work reports the use of novel rare earth
(RE) gettering technique to reduce
background carrier concentration with
nominal baking tirne.
At a RE
concentration of 8xlO atomic fraction
the highest mobility was obtained.
Beyond this while the carrier
concentration and etch pit density
decreased inonotonically , the mobility
also decreased. SIMS and
photoluininescence (PL) studies showed
that the gettering effect was due to
removal of silicon . For InGaAs similar
results were obtained except that the
layer showed type conversion at high RE
concentrt5ion.Otimised layers with n =
2.4 x 10 cm ?ave been characterized
through resistivity, Hall effect, PL and
DXRD measurements. The narrow linewidths
showed the exellent quality of the
layers and interface.The present status
of fiber-optic detectors grown by LPE as
well as MOVPE will be compared as
regards sensitivity, frequency response
and data rate. The performwice of
integrated fiber-optic receivers with
GaAs FET preamplifier will also be
discused.
Silicon ULSI systems: a new communications challenge for optoelectronics
Author(s):
Stuart K. Tewksbury
Show Abstract
Electronic system U3iflfl ULSI wi11 be based on ultrasmall features for ULSI monolithic circuits and on small f eatures for advanced packaging such as multi-chip modules (MCMs). These reduced interconnection cross sections are needed to achieve very high density circuits but may conflict with achieving very high data rates across thos e interconnections. Optical interconnections may provide both very high density interconnections and very high speed data rates. Most comparisons of optical with electrical inter. onnection emphasize the high speed bipolar circuits rather than the high density CMOS circuits. However within VLSI/ULSI systems CMOS interconnections are quite different from and offer several advantages (particularly lower power dissipation at the system level) over bipolar LSI interconnections. The role of optical interconnects is viewed here from the perspective of the CMOS interconnection environment. L
Placing highways in Manhattan street network
Author(s):
R. K. Sanghi;
Ashok Jhunjhunwala
Show Abstract
Several of the high speed optical fibre Metropolitan Area Networks proposed in recent years are slotted networks using deflection muting [1]. Manhattan Street Network is amongst the simplest of these with an underlying Manhattan graph. We propose to place highways in the Manhattan street network. This significantly reduces the delay in the case where packets have to travel long distances. With the reduced delay the network can better support multiple services like packetised voice in addition to data communication. I.
Binary electro-optic node for self-routed photonic packet switching
Author(s):
V. Bharadwaj;
Subrat Kar;
Ananth Selvarajan
Show Abstract
Optical sIf-rt*tsg scheme. inK*iCh packet switched net eo integrated optic direCtiO*aI copIers a*d an all optical scheme employing FmbryPerot de tce have ken ptvpuseL Both the methods make se ofCDMA sequences in their headers msking the process of address recognition simple mechanim. These aeqitences eliminate the seed for atorqe demeists for header processing. 1
Microprocessor based implementation of discrete walsh transform in an optical computing architecture
Author(s):
Asit K. Datta;
Sunit K. Sen;
Anish Deb
Show Abstract
The paper suggests a method of computation of Discrete Walsh Transform (DWT) by matrix vector multiplication which is easier to perform in 2D optical system where processing can be done parallely in 2D. The computation of DWT in such an optical computing architecture is much easier to perform and requires less processing time. A methodology is also proposed where a microprocessor is utilized to sequentially process matrixvector operations on digitized data. The result is stored in the memory for display and/or read out. I.
Ferroelectric thin films for optical waveguides
Author(s):
H. Tiwary;
G. K. Tiwari
Show Abstract
Present work reports successful pre paration of thin transparent homogeous films of ferroelectric TGS and PVF2 by a spin technique and their characterization for application in 10 waveguides. The characterization were done by observing modelines through a spectrometer for the measurement of mode angles. The other important parameter that is required to characterize are refractive index and light propagation loss which have also been evaluated. I
Cr(VI) and Fe(III) doped polymer systems as real-time holographic recording materials
Author(s):
Gurusamy Manivannan;
Rupak Changkakoti;
Roger A. Lessard
Show Abstract
IL EXPERIMENTAL Cr(VI) [as (4)2271 and Fe(ffl) [as FeC1] doped Polyvinyl alcohol and Polyacrylic acid systems have been employed'' as real-time holographic recording materials. Holograms have been recorded in Dicbmmated Polyvinyl alcohol (DCPVA) Dichromated Polyacrylic acid (DCPAA) and Ferric chloride Polyvinyl alcohol (FePVA) films. Various chemical and physical parameters influencing the holographic performance have been optimized. L
Ultrafast optics and microwave technology
Author(s):
Chi Hsiang Lee
Show Abstract
Applications of ultrafast optics to microwave technology are reviewed. A time domain broad band sparameter measurement technique has been demonstrated. On-wafer phase locking of a free running microwave source to the optical pulses is also reported. Some of its applications are discus''sed. I.
Optically controlled characteristics of HEMT
Author(s):
B. B. Pal;
H. Mitra;
Dharmendra P. Singh;
S. N. Chattopadhyay
Show Abstract
The effect of optical radiation on the electrical characteristics of a HENT device has been carried out. Both photovoltaic effect in the metalsemiconductor junction and photogeneration of carriers in the space charge layer of n-A1GaAs HENT device have been taken into account. Offset voltage is found to decrease with flux density and active layer concentration. The drain current is observed to increase with the increase in radiation flux density photogeneration of electronhole pairs. The photovoltaic effect develops a forward voltage across the metalsemiconductor junction. In a A1GaAs/GaAs system the electrons and holes generated in nAlGaAs layer are separated out from each other by the field across the'' metalsemiconductor junction and heterointerface. Thus due to the additional charge carriers the charge density in 2DEG at the heterointerface of the HENT structure will be modified. The theory is given in the next section. Theory The optical HENT structure is shown in Fig. 1 . The region between the Schottky gate and the heterojunction interface is assumed to be totally depleted and the electrostatic potential v2 at the end of the semiconductor (x d2) is obtained by solving Poisson''s eqn. 2 - '' [N2(x) + n(x)(1) dx2 alongwith appropriate boundary condition N2(x) and 2 are the doping concentration and permittivity of n-A1GaAs layer. n(x) is the Photonic devices find a lot of applications in optical communication integrated optics and optical computer. High speed devices
Design and performance of corrugated waveguide structures based on slab waveguide principles
Author(s):
Raj Ayekavadi;
C. S. Yeh;
Jerome K. Butler;
Gary A. Evans;
Paul J. Stabile;
A Rosen
Show Abstract
A simple design is developed for corrugated waveguides for operation in the millimeterwave range of frequencies. The method determines both the corrugation period and the depth. The design is based on slab waveguide principles and uses solutions of the (scalar) boundary value problem of the slab waveguide to determine the corrugation depth and the corrugation spacing. The design tecimique compares well with other techniques developed for the purpose. Reflections at 90 at certain specific wavelengths are measured in the far field to obtain the radiation patterns. The patterns show good agreement with theoretical predictions confirming the effectiveness of design principles used. Measurements range in the frequencies from 90 GHz to 100 GHz. 1.
Antiresonant decoupling of parallel dielectric waveguides
Author(s):
Carlo Gian Someda
Show Abstract
Two open waveguides separated by a finite spacing can be decoupled if the index between them is a suitable function of the transverse coordinates. The proof of this statement relies on vector properties of e. m. waves. On the contrary decoupling is impossible for scalar waves. Therefore it is incompatible with the weakly-guiding approximation. However numerical results and other ones based on perturbation theory show that it can be ohtamed with index differences which are still small enough to be practical. Decoupling can be interpreted physically as an antiresonance of the region between the guides. Examples are presented and potential practical applications are outlined. I.
Three-dimensional analysis of a tapered waveguide structure by a doubled-grid finite-differences method
Author(s):
M. Kunz;
Lubomir Sumichrast;
Walter E. Heinlein
Show Abstract
In this work 3D techniques based on finite
difference (FD) schemes will be introduced to efficiently
simulate the wave propagation in both longitudinally variant and invariant InP based devices. For a
longitudinally invariant medium whose refractive index
does not vary along propagation direction, we have chosen
a step-index channel waveguide and determined the
intensity distribution of the fundamental mode. As a
longitudinally variant integrated optic structure, a tapered
waveguide is selected which is commonly used as a beam
transformer for butt-joint coupling of the above mentioned
rectangular waveguide to a fibre. According to both
structures two different FD techniques are chosen to permit
a numerically more effective investigation as against the
split-operator fast- Fourier transform (FFT) method, also
known as the Beam-Propagation-Method (BPM). This
paper consists of three sections. In the first chapter the FD
method will be investigated in comparison with the BPM
and its capability for solving a variety of integrated-optics
problems will be emphasized. The second chapter
describes the analytical background of the propagation
algorithms used in this paper. Numerical results obtained
by the application of the developed algorithms to the above
mentioned two devices will be given in the last chapter.
investigation of perhaps most complex integrated optics
structures in order to finally determine the optimized
design of the optical device before going into production.
Since none of the existing methods is universal, one must
choose a simulation method according to the given problem
or think of developing something new. In this work we
show that for two different structures two different FD
methods are capable to tackle the given simulation
problem. Each method has its advantages and
disadvantages.
Modal analysis of discontinuities in diffused optical waveguides
Author(s):
Andreas Weisshaar;
Vijai K. Tripathi
Show Abstract
The modal solutions of an arbitrary graded-index
dielectric slab waveguide have been derived by applying the
generalized telegraphist's equations to the equivalent inhomogeneous
parallel-plate waveguide model with electric or
magnetic walls. These solutions have been employed in a
mode-matching procedure to calculate the transmission
properties of step discontinuities in diffused optical waveguides
having exponential, Gaussian and complementary
error-function index profiles. For slab waveguides contaming
an abrupt offset, the radiated power is found to
increase smoothly with increasing displacement. Power
loss calculations for an abrupt change in the diffusion depth
show a sharp transition from almost zero loss to nearly total
radiation loss in the vicinity of the cutoff wavelength
associated with the dominant mode.
Application of electron beam lithography to produce corrugated surface for DFB lasers
Author(s):
P. R. Deshmukh;
Mulayam Singh;
Kamal Jit Rangra;
W. S. Khokle;
B. B. Pal
Show Abstract
For long wavelength single node
DFB type laser devices it Is required to
rrugate the surface of InP substrate in the
form of lines (Grating) with spatial period In
sub-half micron ng. Electron beam
lithography (E2L) can be used to make such high
resolutlon lines first in the resist and then
these lines can be transferred to the substrate
by suitable dry or wet etching process. In
delineating such closely spaced lines In the
resist which Is coated on a relatively high
average atctnic number substrate ( At.No.32),
the well known proximity exposure (PE) effect
associated with EBL requires cxrrection • The
paper discusses arid gives the simulation
results which depict the effect of PE on the
width and spacing of lines. A comparison Is
made between the lines on the lower At.No.
substrate Si, and high At.No. InP substrate. A
proximity exposure compensation (PEC) scheme
based on dose variation technique is found to
provide just adequate correction to PE effect.
The experimental results on the delineation of
lines before and after correction show good
agreement with the simulated results within
experimental limitations.
Rapid thermally annealed ohmic contacts to high temperature Zn implanted InP
Author(s):
C. S. Sundararaman;
John F. Currie
Show Abstract
Silicon close contact rapid thermal annealing (RTA) behavior of heated Zn implants in lnP at low doses 5E11-1E12 ions/cm2 has been studied in the temperature range 800- 900C. Annealing at 800C for 1 0 seconds results in 90+ activation with acceptable profiles. At temperatures above 800C the implant profiles are considerably broadened and exhibit anomalous diffusion tails. The shape of the dopant profile and the position of the peak ion concentration are influenced by phosphorus out diffusion from the sample surface and bulk impurity redistribution du ring the activation process. RTA annealed Au/Zn/Au alloyed contacts were formed on the activated regions in the temperature range 350-450C and the contact resistivity was measured by the Transmission Line Method (TLM). A minimum contact resistivity of 24 xlO-3 a-cm was obtained for the sample annealed at 400C for 5 minutes. X- ray Photoelectro n Spectroscopy (XPS) depth profiles show significant Zn and Au in-diffusion into the substrate at 400C. I.
Recording materials based on vinyl polymers for holography and nonlinear optics
Author(s):
Roger A. Lessard;
Christian Malouin;
Rupak Changkakoti;
Gurusamy Manivannan
Show Abstract
Photopolymers offer excellent pmperties such as ease of handling low cost and real-time recording for the application of holography and non-linear optics. A Vinyl Polymer viz. Polyvinyl Alcohol has been employed for holography and non-linear optics. In this paper results of our experimental investigations on dye/polymer systems for real-time holographic recording and non-linear optics are reported.
Unified approach to nonlinear pulse propagation in optical fibers and self-focusing
Author(s):
Ajit Kumar
Show Abstract
Nonlinear pulse propagation in optical fibers and stationary self-focusing of laser beams in nonlinear media are
investigated using the invariant of motion method. It is shown that this method is not only effective for the solution of
problems related to nonlinear propagation in quasi-optics but also algebraically simple and yields results faster.
In the first case it enables one to follow the dynamical interplay between dispersion and nonlinearity in detaiLthe
knowledge of which is essential for applications to soliton based communication system. In the second case,unlike paraxial
ray theory ,it takes into account the spatial characteristics of the whole beam and shows that the real critical power for
self- focusing should be at least four times the critical power given by paraxial ray theory.
Optical phase conjugation studies in metal substituted tetraphenyl porphines
Author(s):
B. R. Prasad;
Sangeneni Mohan;
C. K. Subramanian;
P. S. Narayanan
Show Abstract
Optical Phase Conjugation studies have been carried out on five different metal substituted Tetraphenyl Porphines. The dependence of conjugate efficiency on perturbation of u-electron cloud of porphine ring by different substituted metals solute concentration solvent parameters intensities and quantum efficiencies have been investigated. I. Intrrxiuctiort: Tetraphenyl Porphines form the basis of many biological molecules including hae moglobin and chlorophyll. However their ability to absorb visible radiation strongly and their conjugated double bond structure allows us to keep them within the general classification of dye molecules. The structural formula of the free base tetraphenyl porphine (H2TPP) is given in fig. 1. Other porphines can be formed by substituting the two centre hydrogens with a metal. The presence of this metal perturbs the yr-electron cloud in the porphine ring and this perturlxition is dependent on the substituted metal. Porphines therefore appear to be an excellent model system in which one can investigate the effects of perturbing a u-electron system by DFWM. Porphines exhibit the phenomenon of reverse saturable absorption i. e. a decrease in transmission with increasing intensity of incident radiation. This occurs if the absorption 257 cross-section from the excited state up to a higher excited state is larger than the absorption from the ground state to the excited state. In this paper we present the details of phase conjugation studies on five metal substituted te traphenyl porphines: (1)Al TPP (2)Co TPP
Optical feedback induced asymmetries in semiconductor laser characteristic curves
Author(s):
Marziale Milani;
S. Mazzoleni;
Franca Brivio;
Guido Chiaretti
Show Abstract
An analysis of the asymmetric response from the device facets is performed. Attention is devoted to the mechanisms that make the feedback adversely affect differential quantum efficiency in a single-mode laser. A key is obtained to the description and control of the non-linear P-I relationship in the region just above threshold (kink).
Tunable UV-VIS-NIR laser
Author(s):
Gopal C. Bhar;
S. Das;
P. Datta
Show Abstract
U1travio1t radiation down to 47nm and infrared radiation upto 3. 4 has been qenerated by second harmonic generation surn+requency mixing and di++rence-- +rquency mixing in a Barium Borate cryutal . The bai c pump 1 aser used I s 1064nm Nd:YAG laser. The other tunable pump source is derived from dye laser. The generation is made by nonco). linear i nteract 1 on. 1.
Polarization characteristics of quantum well lasers
Author(s):
Amit Bandyopadhyay;
Atul Kumar Srivastava;
Sudeep Banerjee;
B. M. Arora
Show Abstract
The existing model of Fermi sea shake
up to explain the excess transverse magnetic
component in optical emission from quantum well
lasers is inadequate beyond the lasing threshold
condition. In this paper we propose that when
lasing occurs the heavy hole wave-function loses
directionality and has equal projections in x,
y and z directions.
Advanced optoelectronic systems for satellite configuration
Author(s):
T. K. Alex
Show Abstract
Configuration. of artificial satellites for communication remote sensing and scientific investigations at present is based requirements of payload or experiment within the constraints of weight volume and power available and utilizes existing proven technologies. The advances in opto electronic components and systems have opened up a new dimension in designing satellites of the future incorporating new technologies. This paper deals with general ideas on configuring satellites based on advanced opto electronic systems wherever applicable. 1.
Advances in quantum well lasers
Author(s):
Niloy K. Dutta
Show Abstract
The fabrication and performance characteristics of InGaASP/InP and strained JnGaAS/GaAS InGaAS/IIIP quantum well lasers are described. Recent results on low threshold high power low absorption loss low chirp and low linewidth which results in new system applications are presented. I. SUMMARY Quantum well (QW) lasers fabricated using the AlGaAs/GaAs material system has been extensively studied and these devices show improved performance characteristics than regular double heterostructure lasers. The fabrication of quantum well lasers require very high perfection of materials growth and interfaces. Such high perfection has been achieved using MOCVD (metal organic chemical vapor deposition) growth technique for In_p based materials. As a result it has been possible to fabricate high performance unstrained and strained InGaAsP/lnP quantum well lasers and examine the performance improvement for system applications. For GaAs based materials QW lasers can be fabricated using both molecular beam epitaxy (MBE) and MOCVD growth technique. The principal advantages of QW lasers over regular double heterostructure (1)11) lasers are (i) lower threshold current density (ii) lower optical loss which can result in low threshold current and higher power and (iii) lower dynamic linewidth under modulation which results in longer repeater spacing for optical fiber transmission ms The parameters for optimization of a quantum well laser structure are the well and barrier widths barrier composition and grading for a graded index separate confinement heterostructure (GRIN-SCH) design. The 137 schematic of QW laser
Wavelength and polarization selectivity in external cavity diode laserswith frequency selective feedback
Author(s):
George Guekos;
Dimitris Syvridis
Show Abstract
The paper reviews recent results obtained with diode lasers used in external hybrid cavities with frequency selective feedback. Very wide discreet tunable ranges are achieved. They can be made to oscillate in a tunable mode having the desired polarization state TE or TM. High-speed polarization switching in the GHz range is possible by inserting passive or active polarization selecting elements in the cavity. Hybrid external cavities are attractive for applications in optical metrology spectroscopy and optical communications.
Characteristics of erbium doped fiber lasers
Author(s):
P. Gopalakris Nair;
Mridula Joshi;
B. M. Sivaram;
J. P. Raina
Show Abstract
This paper presents the study of an Erbiua
ioped multicomponent glass fibre laser pumped
Dy ar Rrgui ion laser. Frequercy tunabiIity
is achieved through shift of laser spectra with
pump power and fibre Iength.The linewidth of
the output and its variation with pump power
'ere Iso studied.
Integrated optoelectronics for optical interconnections and optical signal processing
Author(s):
Osamu Wada
Show Abstract
Integrated optoelectronics using 111-V compound semiconductor technology is expected to offer new techniques of interconnection and signal processing within electronic digital systems solving the wiring limit in data communication and processing using the advantages of optical technique such as high data transmission rate and high parallelism. Optical interconnection devices are the key to this and the development is being carried out not only to multiplex a vast amount of data but also to provide flexible interconnection functions. This paper summarizes the role and current status of integrated optoelectronics technology for optical interconnections and signal processing systems. 1.
Fabrication of a 2-D integrated optic array illuminator
Author(s):
Ashok N. Kaul;
D. Mohan;
Prakash C. Mehta
Show Abstract
Array illuminators find wide applications not only as optical distributors for an array of optical devices but also as key elements for optical interconnects . We have evolved a simple and a straight - forward method to fabricate a two - dimensional integrated optic array illuminator that is capable of generating multiple twodimensional beamlets . Two identical plane holographic gratings orthogonal to each other were multiplexed on a photosensitive emulsion coated glass waveguide . On coupling a laser beam from the side opposite to the emulsion multiple parallel beams travelling normal to the surface are generated . Experimental details and results are reported.
Effect of controlled vacancy injection by ion implantation on the intermixing of InGa/GaAs quantum wells
Author(s):
William P. Gillin;
Kevin P. Homewood;
Brian J. Sealy
Show Abstract
- The diffusion coefficient of interdiffusion in InGaAs/GaAs strained quantum wells has been determined as a function of time following implantation with gallium arsenic and krypton ions. All implants were shown to produce some collisional mixing. Gallium implantation produced no enhancement of the intermixing over unimplanted samples whilst krypton implantation produced a factor oftwo increase in the interdiffusion. Arsenic implantation produced a two step diffusion mechanism with a fast initialdiffusion(20 times unimplanted)and a steady state region similar to that observed with krypton implants. I.
Interface structure of CoSi2 and HoSi2 epitaxies on silicon
Author(s):
Sharath Dakshinamurthy;
Krishna Rajan
Show Abstract
The occurrence of the defect structures in heteroepita. xies can be attributed to some low energy configuration of atoms at the interface which also result in specific orientation relationships between the epilayer and the substrate. Here we apply a generalized model to characterize the interfaces of CoSi2 and MoSi2 with silicon and compare the predictions of the models with TEM observations of the defect structure.
Negative resistance characteristic in optoelectronic composite device
Author(s):
M. Satyam;
Krishnaswamy Ramkumar;
M. Anadan
Show Abstract
This paper describes the nagative resistance characteristic exhibited by a composite optoelectronic device consisting of a liquid crystal display and a phtoconductor. This characteristic is suitable for memory devices optical pattern generators and special oscillator circuits. Devices like SCR UJT Tunnel diode are known to exhibit negative resistance characteristics and hence electrical bistability (1) A liquid crystal display (LCD) (2) in series with a photoconductor (PC) is known to exhibit optical bistability (3 4). The electrical characteristics of this or any other combination of these devices has to our knowledge not been reported so far. It is found that a parallel combination of these devices exhibits a negative resistance characteristic which is described below. Fig. I Structure of the LCD-LDR optoelectronic device. 274 transparent LCD is connected to a PC in parallel and placed such that the light passing through the LCD falls directly on the PC. The transmmission characteriastic of the LCD is given graphically as shown in Fig. 2. To a first approximation the transmittance T of the LCD can be expressed as T Tmax when A V VB T Tmax - K(V - VB) when VB I '''' T Tmin when VC V VD where I Initially the transmittance of the LCD is Tmax and hence the resistance of the PC is Rein which may be approximately written as Fig. 2 : Transmission composite characteristics of the
High contrast optical switching in electrochromic Prussian blue films for display/window applications
Author(s):
V. Vinni;
L. K. Rao;
N. Munichandraiah
Show Abstract
A novel but simple high contrast optical switching suitable for display! window applications is demonstrated. The technique is based on electrochromic effect in electrochemically prepared prussian blue (PB) film. The switching action is observed through a colour change from dark blue to total trans prency by simultaneous insertion of K ions and electrons into prussian blue lattice. The device performance and its improvement over the presently known state of the art technology using prussian blue films are also briefly discussed. 1.
Defect mapping system for optoelectronic materials
Author(s):
K. S .R. K. Rao;
K. R. Ramakrishnan;
Vikram Kumar
Show Abstract
The defect mapping system is built on the principle of Scanning Optical Microscope (SOM). It''s essentially an optical probe with an xY translational stage and a Data Acquisition System (DAS). The SOM can be used in three different modes namely Reflection Transmission and Light Beam Induced Current (LBIC). In this paper the instrumentation and it''s capability as SOM and in LBIC mode has been demonstrated. I
Fabrication of singlemode waveguide devices by inverse ion-exchange in glass
Author(s):
Prafulla J. Masalkar;
Rajpal S. Sirohi;
Vuyyuru Venkateswara Rao
Show Abstract
The inverse ion-exchange process in glass is
studied with the aim of fabricating single mode
waveguide devices. Single mode channel
waveguides arc fabricated by ion-exchange. The
process is modeled using finite difference technique
and the effects of various experimental
parameters on the refractive index profile of the
waveguide are studied.
Preparation of low-dislocation density and semi-insulating InP using LEC technique
Author(s):
V. Jagadeesh Kumar;
P. Ramasamy;
R. Fornari
Show Abstract
Indium Phosphide is a
semiconductor which is very useful for
applications in the field of micro and
optoelectronics. Growth of InP bulk
sin9le crystals by Liquid
Encapsulation Czochralski (LEC) is
stil a major problem of scientific and
technological importance. The lack of
a suitable dopant to reduce the EPD
without enhancing the number of free
carrier concentration has been
eliminated by the addition of codopants,
namely Cadmium and Sulpihur.
In the present work, it will be shown
that it is possible to obtain LEC
boules having n-type conductivity over
the entire crystal length with a
distribution of carriers more
homogeneous than in crystals doped,
for instance with sulphur alone. The
doping procedure adopted leads to a
good evaluation of the segregation
coefficient of Cadmium in InP. The
coefficients reported in the
literature are so scattered that it is
difficult to set accurately the amount
of dopant to be added for obtdining
the desired doping level. A variety
of dopants have been made use of to
understand the nature of dopants and
their role in the structural and
electrical characteristics of the
crystal.
Time domain simulation and modeling of Si-GaAs MSM photodetectors
Author(s):
R. T. Kollipara;
Thomas K. Plant;
Vijai K. Tripathi
Show Abstract
The two-dimensional modeling of the
semi-insulating gallium arsenide (SI-GaAs) interdigitated
photodetectors is presented. The model considers full bipolar
transport, effects of nonuniform carrier generation, field
dependent mobilities, carrier diffusion, recombination and
includes the effects of the external circuit elements. Dynamic
simulation is performed after applying an ideal optical
impulse and the simulated response is compared with the
experimentally observed response.
Monolithic MSM photodetector/amplifier optical receiver on GaAs substrate
Author(s):
D. C. Dumka;
Mousumi Mazumdar;
M. S. Yadav;
Babu Ram Singh
Show Abstract
A monoli thi c opti cal rcei vex' consisting
of an MSM-PD and MESFET anp1ifiez' for
near 850nrn wavelength applications has
been designed and fabricated on GaAs
substrate. The parameters avaluated on
fabricated test structures such as 1pm
MESFET and MSM-PD were used as the model
parameters for receiver circuit simula
tion. The mesa epitaxial 1pm MESFET. technology
was used for receiver fabrication.
The receiver module characterized for
output response showed values close to the
simulated values of 3dB upper cut-off
frequency of 370MHz with a flat trazis impedance of 3.5KQ.
Wideband high-gain optical preamplifier
Author(s):
F. Giannini;
C. Paoloni;
G. Orengo
Show Abstract
The increased use of high data rate in optical systems brings to stress the receiver performance both in sensitivity and in bandwidth. Among the others the monolithic GaAs technology (MMIC) seems to be extremely suitable for this kind of applications. In order to achieve the best results from this new approach a series of design guidelines are given for Gigabit rate DC coupled transimpedance amplifier used as optical front-end. Two solutions are also presented and experimental results are displayed to confirm the reliability of the theoretical simulation. 1.
FIR generation by optical down conversion
Author(s):
Rakesh Kumar Tyagi;
V. V. Rampal
Show Abstract
Techniques for the generation of far infrared (FIR) radiation through optical mixing process have been discussed. Methods for estimating the phase matching angle angular width of phase matching and power output of the FIR source have been given. Experimental results obtained through optical difference mixing of two orthogonally polarized dye laser frequencies have been quantif ied. 2.
Computer simulation of FPN limited NETD in MCT FPAs
Author(s):
Vikram Dhar;
Vishnu Gopal;
K. C. Chhabra
Show Abstract
The NETD is calculated in FPN limited
MCT FPAs, on the basis of a model in
which two-point compensation is used
and the readout contribution to FPN is
not considered. It is shown that the
lowest NETD is obtained when x is
about 0.235 in MCT.
High-gain GaAs MSM photodetector
Author(s):
V. T. Karulkar;
S. C. Purandare;
Atul Kumar Srivastava;
B. M. Arora
Show Abstract
Photodetectors with metal-semiconductor
-metal (MSM) structures having very high quan
turn efficiency are investigated to identify the
gain mechanism. From the temperature dependence
studies impact ionisation of carriers in a region
under the edge of the cathode is shown to be the
predominant gain mechanism.
Metal-Semiconductors-Metal (MSM) structure
has recently emerged" 2 as an attractive device
for photodetection due to its simple planar tech
nology which can be easily adapted to optoelec
tronic integration. The other features of MSM
photodetector are their high sensitivity, low
capacitance, low dark current and high speed.
Substatial amount of work has been done on GaAs
MSM photodiodes which are useful in near infrared
wavelength regime. Devices with very low dark
current (lOOpA at 1OV for 200x200pm geometry) and
low rise and fall times (23 and 55 ps respecti
vely) have been recently fabricated on semi-insu
lating (SI) GaAs substrates1. The other interest
ing feature of MSM structure is that it has in
ternal gain. Despite intensive study of these
devices there is still confusion about the physi
cal origin of the gain in these devices. Ito
et a13 attribute the gain to hole injection at
the forward biased anode contact. Measurements
of Zirngibl et al however, point to avalanche
mechanism of gain in these devices. In this
paper we report the results of experimental in
vestigation of gain mechanism in GaAs MSM struc
tures which have extremely high gain (100).
Design and development of a 4x4 photonic switch
Author(s):
Bagula V. Sankrithyan;
G H Sarma;
Arati Prabhakar;
Srinivasan R. Natarajan;
Ananth Selvarajan
Show Abstract
The design of a 4x4 switch module of blocking architecture based on Ti:LiNbO3 has been developed and attempts have been made to fabricate the device. The design methodoogy and fabrication details are described. 1.
Recent developments in the optical measurement of surface fields on silicon photoconductive power switches
Author(s):
Harshad P. Sardesai;
William C. Nunnally;
Paul Frazer Williams
Show Abstract
We report further investigations of the surface electric fields present between the contacts ofan optically controlled silicon switch. The Kerr electro-optic effect and a phase sensitive interferometric analyzer is used to measure the surface fields when a pulsed high voltage is applied across the contacts. The experimental arrangement has a temporal resolution of 100 nanoseconds and a spatial resolution of 50 microns. The experimental results show preferential field enhancement near the anode and the surface electric fields are nonuniform in space and time. The temporal non-uniformity is more pronounced at higher electric fields.
Circuit modeling of multimode semiconductor lasers and the effect of fiber dispersion on the intensity modulation
Author(s):
K. K. Kamath;
P. R. Vaya
Show Abstract
A c irclAl: L mode 1 for Laser diodes based ort nu I C z. mode ra t e eqtiat tons i. s presert t ed hre. be I ay 1 i ries are cornec t ed aL the outpt nodes iduch provide de Lays corresponding to reLative propaation de 1 ays D7i for L aser Lorii LILdZ. ia I modes L!. . ) . n w optical fiber. Th(s modeL s(iruLat. d lASCfl3 th* c(reut s(nwLa LLOTt pacha6e SPICE2. The results were compared with those resuLts by the dtrect rtv soLution of th muLti mode rate equations.
Photo induced refractive index changes in two-mode elliptical core fibers: Applications
Author(s):
Ashish M. Vengsarkar;
Jonathan A. Greene;
Kent A. Murphy
Show Abstract
Photoinduced refractive-index gratings are shown to affect the differential phase modulation between the LP and LP11 modes copropagating within the core of a germanium-doped (Ge-doped) two-mode elliptical-core (e-core) fiber. The beat length of fibers containing such gratings is shown to vary as a function of strain applied to the fiber leading to a new type of weighted optical fiber sensor whose sensitivity varies as a function of length along the structure to which it is attached or embedded. This novel type of spatially-weighted distributed fiber sensor is shown experimentally to function as an efficient vibration mode filter by enhancing either the first or second mode of a thin cantilever beam. These results support future applications of spatially-weighted/distributed optical fiber sensors for the evaluation and control of vibrating structures. I.
Three waveguide polarization splitter based on resonant tunneling
Author(s):
K. Thyagarajan;
S. Pilver
Show Abstract
We propose the design of a novel and highly efficient all dielectric three waveguide polarization splitter based on the phenoRenon of resonant tunneling. By consideriang a glass waveguide structure with an intersediate high index guiding layer (such as a i 1 icon) we show that one can obtain extinction ratios better than -30 dB in both the outer waveguides at a particular thickness of the high index layer. The proposed configuration should be of interest in the design of inline fiber optic polarization splitters and in integrated optics. I.
Multilayer waveguide with metal or absorbing layers: an exact numerical procedure
Author(s):
Enakshi Khular Sharma;
Mukesh P. Singh;
V. L. Gupta
Show Abstract
We present here an exact numerical procedure to obtain the propagation constants of multilayer lossy waveguides in which the complex eigenvalue problem is solved in real domain and hence it is most suitable for Personal Computers. We also report a first order technique in which once the real eigenvalue problem is solved the ohmic loss due to a small imaginary part is obtained analytically. 1
Numerical analysis of back scattered signal in infrared optical fibers
Author(s):
Mandavilli Mukunda Rao;
Chenniappan Ravichandran;
P. Mythili
Show Abstract
M. MukUndaraO Indian Institute of Technology Madras-600 036 V. C. RaVihaiidran and P. Mythill Anna University Madras-600 025 With the increasing use of fluoride fibres tor communication in the infrared region OTDR technique (1) has been extended conceptually for fluoride fibres in the wave length range 1. 5urn - 4urn. OH is found to be the rnajQr contributing factor whose possibility to be monitored by means of an OTDR- are discussed. I NTRODUCT I ON The most exciting prospect for optical fibres made from fluoride glasses is the possibility of prvoldlng long distance optical communication systems without the need for repeaters and amplifiers. ZrF4 baed glasses are pi''ominent in particu I ar 2 rF4-BaF2-LaF3-A I F3-NaF (2BLAN) offer good properties. Considering the various loss mechanisms the outcome is that fluoride based optical fibre exhibits a low loss window at 2. 53 urn with a theoritical minimum loss approaching 0. 04 dB/KM. Fluoride fibres can transmit both infrared and visibie light. They have many applications outside the field of telecommunications including opticai fibres sensors in remote infrared Spectroscopy'' iaser s''rgerv and ribre 119 lasers. Fluoride glass fibres have high transition temperature and refractive indices conpared to silica glass fibres. the of fluorides is that they have a high rate of crystallization which complicates the fibre fabrication process. The reported minimum loss has remained unchanged iP the 2. 5 pm windiw region
Analysis of Cerenkov second harmonic generation in optical waveguides
Author(s):
R. Balasubramanian;
Talabuttala Srinivas;
Ananth Selvarajan
Show Abstract
We pre8enI i c. spled mode analysis on Cerenku Second Hatrmonic Ceneration(SHG) 1. find osl nsmer ledly the harmonic power planar wave side. B. lh TE and TM modee are considered. The ci. fed of variatien 0/ use g*idc parameters on the cnivcru. n efficiency sa prcacnled. Nmerica1 reaI1a are preP 8enIeifor prolen e:changeililhi*m niohaie(FE:LiNIO6) vdvegvides. Improved cospling c. efficienta are used. Estension of the present s1dy te optical flere ie of lined. I
Determination of the refractive index profile of integrated optical waveguides from near-field measurements
Author(s):
M. Halfmann;
Lubomir Sumichrast;
Walter E. Heinlein
Show Abstract
The refractive-index profile of optical
waveguides can be obtained from transmitted near-field
intensity measurements by the method of transverse offset
scanning. As the calculation of the refractive-index profile
from the scalar wave equation requires the second
derivative of the field distribution, we developed a
modified measurement setup, the modulated transverse
offset scanning method.
Performance analysis of optical FSK heterodyne receiver employing discriminator detection
Author(s):
Debasish Datta;
Debashis Goswami;
Shri A.N. Srivastava
Show Abstract
The present work deals with the performance analysis of an optical FSI( heterodyne receiver einpioying limiter-discriminator detection ( LDD). The analysis is carried out with due considerations to laser phase noise and FM clicks at discriminator output. The receiver performance is assessed from the plots of bit error probability (BEP) versus IF SNR for various combinations of IF bandwidth frequency deviation az laser Jinewidth. The results indicate that an optical heterodyne FSK receiver employing LDD can achieve a BEP floor for suttable combinations of IF banawidth arid frequency deviations with moderate laser linewidths ( 5/. ). This suggests an easier implementation of NCFSK heterodyne optical receivers with a reasonaDie tolerance to the laser phase noise. I.
Coherent communication system
Author(s):
Shirshu Varma;
M. L. Rampal
Show Abstract
The prospects of using Coherent Communication techniques is -to increase the inlorniation Capacity of an optical link, which has been widely appreciated for more than 20.years. Earlier, in optical fiber communication systems, ono±'1 intensity modulation and direct photo detection were most commonly ado— pted. In these systems, the receiver sensitivity is limited by the detector and amplifier noi8es. Indeed optical communication systems which use heterodyne or homo—dyne detection are common— ly referred as "Coherent Communication Systems" .
Interrelation among optical fiber parameters - dispersion, rise time and bandwidth - in high-speed communication systems
Author(s):
K. R. Subramanian
Show Abstract
Dispersion in optical fibers and rise time in electro-optic components are very important parameters in the design of high speed optical communication systems. Dispersion parameter is used to determine the bandwidth capability of the optical fiber. Rise time parameter is used to estimate the bandwidth capacity of the overall transmission system comprising transmitter fiber and receiver. Both dispersion and rise time parameters are treated in isolation in technical literature. An approximate relation between these two parameters in conjunction with the bandwidth estimation has been derived and presented in the paper.
Modeling of fiber optic transmission systems
Author(s):
V. K. Dubey;
M. Kameshwar Rao
Show Abstract
This paper describes a model suitable for simulation of optical fiber communication system for transmission of digital data. The model is based on the idea of defining the spectral function for each of the sub-system like transmitter fiber and receiver. To evaluate the system performance an overall spectral function is computed and used as a model for computer simulation. A PC based software is developed using this model. To estimate the validity of the simulation program a set of results were generated using the system parameters obtained from previously published work. The simulation results and the experimental results are found to be very close. The simulation program is also capable of generating eye diagrams for a given set of system parameters.
Optical processing of images from a military environment
Author(s):
Emile J. Schweicher;
Frank Dubois
Show Abstract
Several pure optical processing methods have been investigated in order to improve the quality of images from a military environment. Two methods proved unsuitable from the military viewpoint: the well know Vander Lugt matched filter and the classical spatial filtering by a 4f system with coherent illumination. On the other hand two other methods gave encouraging results : pseudocolour encoding of spatial frequencies and cryptography by means of a double aberrating medium. I.
Coherence length measurement by phase conjugation: a novel technique
Author(s):
Chander Bhan;
Kondragunta Syam Sunda Rao;
Prakash C. Mehta
Show Abstract
The present paper reports a simple method for measurement of temporal coherence of a laser using holographically generated phase conjugate wavefront employing an iron doped LiNbO3 (0 . 1 ) crystal . In this method one has to see only the presence of a laser point on the screen rather than to observe interference fringes as in Michelson method. 1 .
Fiber optic sensor based on evanescent wave absorption
Author(s):
Periasamy Radhakrishnan;
V. P. N. Nampoori;
C. P. G. Vallabhan
Show Abstract
The design and performance of a fiber optic sensor working on the principle of evanescent wave absorption are described. Using this sensor the rate of a standard chemical reaction is determined. The measured value is compared with that obtained using a spectrophotometer. I.
Optical implementation of trinary combinational logic incorporating Fredkin gates
Author(s):
Amitabha Basuray;
Mina Ray;
B. Ray
Show Abstract
In the present report several implementation of trinary logic functions using three logical values 1 0 and 1 will be presented. Fredkin gate having three input and three output lines has been suggested as a basic building block of an optical computer. In this paper a binary coded trinary (BCT) method has been used to represent each trinary number and several similar logic functions in blocks using Fredkin gates are proposed. I.
Simulation of optical front-end AGC amplifier for gain adding/current dividing configurations
Author(s):
Tatipamula Mallikarjun;
J. P. Raina
Show Abstract
In this paper design simulation and optimization of AGC amplifier for the frontend receiver of the high speed optical transmission system have been done. Characterization of Gain Adding Current Dividing and Modified Current Dividing type AGC amplifiers using spread of the transistor parameters as well i. e. frequency response dynamic range and dependence of the output DC level fluctuations on gain variation are investigated and compared. I.
Optical MSD symbolic substitution system based on a higher ordered rule
Author(s):
A. K. Reddy;
Tatipamula Mallikarjun;
J. P. Raina
Show Abstract
The advantages provided by Photonic
Computing has been well documented. An
Optical arithmetic processor has to take full
advantage of the massive parallelism in
optical signals. Such a processor, using the
Modified - Signed - Digit (MSD) number
. (i) representation, has been presented here based
(2) on the symbolic substitution 1ogi. The
higher order symbolic substitution rules are
formulated for the addition operation, which is
carried out in just two steps. Based on the
addition operation, the other arithmetic
operations - subtraction, multiplication and
division - are implemented. Finally, the
usefulness of this MSD system is studied.
Analysis of a single mode curved-fiber optical coupler
Author(s):
Banmali S. Rawat;
R. Shukla;
Ram Prakash Shukla
Show Abstract
The analysis of an efficient, low-loss curved
single mode optical fiber coupler has been presented.
Numerical results for coupling coefficients, effective
interactive length and normalized power as a function of
minimum spacing, wavelength and offset have been obtained. The coupling effects due to vertkal offset of the
fibers have also been determined. This provides an
additional design flexibility for the coupler.
Ultraweak light emission from living material
Author(s):
Devaraj Balasigamani;
Harumi Ito;
Paul Roschger;
Ronald Q. Scott;
Masashi Usa;
Masaki Kobayashi;
Yoshio Taguchi;
Humio Inaba
Show Abstract
Intrinsic ultraweak light emission from cellular nuclei and 2-dimensional photon images obtained on injury to germinating seedlings and mouse are reported and discussed. I.
Semiempirical self consistent calculations of GaAs[III] surface reconstructions
Author(s):
Shashikala Das;
D. L. Dorsey
Show Abstract
Self-consistent semiempirical Molecular Orbital Programs MOPAC and MOSOL
are used for studying the surface restructuring and energetics of gallium arsenide
substrates. The total energy calculations of different cluster sizes to determine the
binding energy of surface layer arsenic atoms indicate that proper bulk termination of
the surface and inclusion of second nearest neighbors is very important. The
comparison of our results with ab initio results is encouraging and indicates the
potential of this approach for studying surface restructuring in semiconductors.
Optically tuned characteristics of an ion-implanted GaAs OPFET
Author(s):
B. B. Pal
Show Abstract
Optically tuned GaAs OPFET Is a potential device for integrated Optics Optical Communication and Computing. The transient analysis of an ion implanted GaAs OPFET shows that the carriers generated in the gate depletion region due to absorption of photons attains the steady state value after 40 ps. The D. C. analysis indicates that a analysis normally ON device becomes OFF at a higher negative gate voltage compared to the dark condition and a normally OFF device is opened even at zero gate bias. The drainsource current and the transconductance are significantly enhanced due to optical radiation. In the a. c. analysis the optical radiation is modulated by the signal and hence the number of electronhole pairs generated below the gate is also modulated. So the device properties are greatly influenced by the modulated frequency.
Photonic Networks
Author(s):
Hari M. Gupta
Show Abstract
This paper discusses photonic network architectures. The low medium and high bit rate implementations have been described. These include Fiber Distributed Data Interface Distributed Queue Dual Bus and Wavelength Division Multiplexed Networks. iL
An automatic angular positioning of mask with wafer using modified moire technique
Author(s):
Brahm Pal Singh;
Dr. Kowsalya;
Rina Sharma;
Ram Narain;
Alok K. Kanjilal;
Ramesh P. Singh;
Vijay Trimbak Chitnis;
Yoshihisa Uchida
Show Abstract
An automatic and accurate technique
for angular positioning of mask with
respect to wafer is reported.. Alignment
marks are in the form of gratings and the
moire signal is obtained by the relative
displacement between the gratings. The
higher slope region of the moire signal
is used to obtain higher sensitivity and
better position control accuracy. The
experiments are performed with 25 micrometer pitch gratings and Piezo-
Electric Transducer is used for the
angular displacement. The angular
-7
accuracy of the order of 2 x 10 radian is
reported with a time constant of 0.2 sec.
In the recent years, use of moire
interference technique for mask to wafer
alignment has attracted much attention
especially in VLSI fabrication technology
where a highly accurate linear and
angular positioning is involved. In this
technique the alignment marks are in the
form of gratings.
A laser beam is passed normally
through a mask grating and reflected from
the wafer grating. Intensity variation in
the reflection mode due to relative
angular rotation is detected by a
photodetector and converted into the
electrical signal, known as moire signal.
Stable second-order optical non-linearity in novel photocrosslinkable polymers
Author(s):
Lian Li;
X Zhu;
Y. M. Chen;
Jayant Kumar;
Sukant K. Tripathy
Show Abstract
Optical characterization of novel photocrosslinkable second-order nonlinear optical (NLO) polymers are presented. These polymer systems have been designed with nonlinear optical moieties in the polymer main chain. When poled and sufficiently photocrosslinked these polymers exhibit relatively stable second-order optical nonlinearity at room temperature. The linear optical and second-order NLO properties of these recently synthesized polymers have been investigated. Second harmonic generation (SHG) was utilized to monitor the temporal stability of the nonlinearity. The linear electro-optic coefficients were measured with a modified Michelson interferometer. 1.
Photosensitive Phenomenon in optical fibres
Author(s):
Raman Kashyap
Show Abstract
The phenomenon of photosensitivIty in optical fibres covering both Bragg- grating formation and second-harmonic generation is reviewed with emphasis on recent work. Although much is understood more research is necessary to elucidate the mechanisms and unfold the microscopic effects responsible for both observations. This exciting field has grown substantially in past years from fundamental investigations into this curious phenomenon to the applications arena impacting on fibre and semiconductor lasers sensors memory and supervisory application in telecommunications fibre taps and in novel filter applications. Cheap optical fibre frequency converters are a possibility in the future. 1
Opto-elecronics/photonics activities at C-DOT
Author(s):
Anand Srivastava
Show Abstract
This paper briefly describes the opto electronics activities at C-DOT. Some of the ongoing activities
which are described in this paper are design and development of Synchronous Multiplex Optical
Line terminating equipments and regenerators for 'Synchronous Optical Network', low capacity
opti cal fibre systems and optical interconnects for varying data rates.
A modification of the beam propagation algorithm
Author(s):
Shiva Kumar;
Srinivas Talabattula;
Ananth Selvarajan
Show Abstract
A modification of the Beam PropagationMethod (BFM) is suggested so that only one integral has to be evaluated instead of two for every two iteration. This will reduce computational time as well as errors. Also for a medium whose refractive index does not vary along propagation direction we have suggested a matrix method which takes very less computer time as agaiflst the conventional BPM. The method is applied to the combinar tion of microlens and taper. I
Optical detectors and millimeter-wave amplifiers: structures for integration and their performance
Author(s):
Mukunda B. Das
Show Abstract
The modulation-doped field-ffect transistors (MODFETs) based on 111-V materials have demonstrated low-noise and high power gain performance at millimeter-wave frequencies beyond 100 GHz. Use of these devices for high speed optoelectronic receivers will depend heavily on integrated circuits (OEICs) built with optical detector and transistor amplifier structures. This overview paper examines the limitations of compatible MSM detector diode and a transimpedance amplifying MODFET circuit and projects the performance of a receiver based on them with 23 Gb/s response. I.