Carrier depletion based silicon optical modulators
Author(s):
Delphine Marris-Morini;
Gilles Rasigade;
Laurent Vivien;
David J. Thomson;
Frédéric Y. Gardes;
Graham T. Reed;
Jean-Marc Fédéli;
Paul Crozat;
Eric Cassan
Show Abstract
Silicon optical modulators have generated an increasing interest in the recent years, as their
performances are crucial to achieve high speed optical links. Among possibilities to achieve
optical modulation in silicon-based materials, index variation by free carrier concentration
variation has demonstrated good potentiality. High speed and low loss silicon modulators can
be obtained by carrier depletion inside lateral PN or PIPIN diodes. When the diode is reverse
biased, refractive index variations are obtained and then phase modulation of the guided wave
is obtained. Mach-Zehnder interferometers are used to convert phase modulation into
intensity modulation. Experimental results are presented for both PN and PIPIN diodes.
Nonlinear silicon photonics
Author(s):
Kevin K. Tsia;
Bahram Jalali
Show Abstract
An intriguing optical property of silicon is that it exhibits a large third-order optical nonlinearity, with orders-ofmagnitude
larger than that of silica glass in the telecommunication band. This allows efficient nonlinear optical
interaction at relatively low power levels in a small footprint. Indeed, we have witnessed a stunning progress in
harnessing the Raman and Kerr effects in silicon as the mechanisms for enabling chip-scale optical amplification, lasing,
and wavelength conversion - functions that until recently were perceived to be beyond the reach of silicon. With all the
continuous efforts developing novel techniques, nonlinear silicon photonics is expected to be able to reach even beyond
the prior achievements. Instead of providing a comprehensive overview of this field, this manuscript highlights a number
of new branches of nonlinear silicon photonics, which have not been fully recognized in the past. In particular, they are
two-photon photovoltaic effect, mid-wave infrared (MWIR) silicon photonics, broadband Raman effects, inverse Raman
scattering, and periodically-poled silicon (PePSi). These novel effects and techniques could create a new paradigm for
silicon photonics and extend its utility beyond the traditionally anticipated applications.
HELIOS: photonics electronics functional integration on CMOS
Author(s):
Jean-Marc Fédéli;
Laurent Fulbert;
Dries Van Thourhout;
Pierre Viktorovitch;
Ian O'Connor;
Guang-Hua Duan;
Graham Reed;
Francesco Della Corte;
Laurent Vivien;
Francisco Lopez Royo;
Lorenzo Pavesi;
Blas Garrido;
Emmanuel Grard;
Bernd Tillack;
Lars Zimmermann;
Stéphane Formont;
Andreas Hakansson;
Ewald Wachmann;
Horst Zimmermann;
Arjen Bakker;
Henri Porte
Show Abstract
Silicon photonics have generated an increasing interest in the recent year, mainly for optical
telecommunications or for optical interconnects in microelectronic circuits. The rationale of silicon photonics
is the reduction of the cost of photonic systems through the integration of photonic components and an IC on a common chip, or in the longer term, the enhancement of IC performance with the introduction of optics inside
a high performance chip.
In order to build a Opto-Electronic Integrated circuit (OEIC), a large European project HELIOS has been
launched two years ago. The objective is to combine a photonic layer with a CMOS circuit by different
innovative means, using microelectronics fabrication processes. High performance generic building blocks
that can be used for a broad range of applications are developed such as WDM sources by III-V/Si
heterogeneous integration, fast Si modulators and Ge or InGaAs detectors, Si passive circuits and specific
packaging. Different scenari for integrating photonic with an electronic chip and the recent advances on the
building blocks of the Helios project are presented.
Overview of the EU FP7-project HISTORIC
Author(s):
G. Morthier;
R Kumar;
F. Raineri;
R. Raj;
Jens Hofrichter;
Nikolaos Chrysos;
B. J. Offrein;
R. Zhang;
J. van der Tol;
O. Raz;
H. Dorren
Show Abstract
HISTORIC aims to develop and test complex photonic integrated circuits containing a relatively large number
of digital photonic elements for use in e.g. all-optical packet switching. These photonic digital units are alloptical
flip-flops based on ultra compact laser diodes, such as microdisk lasers and photonic crystal lasers.
These lasers are fabricated making use of the heterogeneous integration of InP membranes on top of silicon
on insulator (SOI) passive optical circuits. The very small dimensions of the lasers are, at least for some
approaches, possible because of the high index contrast of the InP membranes and by making use of the
extreme accuracy of CMOS processing.
All-optical flip-flops based on heterogeneously integrated microdisk lasers with diameter of 7.5μm have
already been demonstrated. They operate with a CW power consumption of a few mW and can switch in 60ps
with switching energies as low as 1.8 fJ. Their operation as all-optical gate has also been demonstrated.
Work is also on-going to fabricate heterogeneously integrated photonic crystal lasers and all-optical flip-flops
based on such lasers. A lot of attention is given to the electrical pumping of the membrane InP-based photonic
crystal lasers and to the coupling to SOI wire waveguides. Optically pumped photonic crystal lasers coupled
to SOI wires have been demonstrated already.
The all-optical flip-flops and gates will be combined into more complex photonic integrated circuits,
implementing all-optical shift registers, D flip-flops, and other all-optical switching building blocks.
The possibility to integrate a large number of photonic digital units together, but also to integrate them with
compact passive optical routers such as AWGs, opens new perspectives for the design of integrated optical
processors or optical buffers. The project therefore also focuses on designing new architectures for such
optical processing or buffer chips.
The BOOM project: a new generation of photonic routing subsystems using hybrid integration on silicon-on-insulator waveguide boards
Author(s):
Leontios Stampoulidis;
Konstantinos Vyrsokinos;
Christos Stamatiadis;
Hercules Avramopoulos;
Lars Zimmermann;
Karsten Voigt;
Zhen Sheng;
Dries Van Thourhout;
Jochen Kreissl;
Ludwig Mörl;
Jens Bolten;
Thorsten Wahlbrink;
Fausto Gomez-Agis;
Eduward Tangdiongga;
Harmen J. S. Dorren;
Annachiara Pagano;
Emilio Riccardi
Show Abstract
The European BOOM project aims at the realization of high-capacity photonic routers using the silicon material as the
base for functional and cost-effective integration. Here we present the design, fabrication and testing of the first BOOMgeneration
of hybrid integrated silicon photonic devices that implement key photonic routing functionalities. Ultra-fast
all-optical wavelength converters and micro-ring resonator UDWDM label photodetectors are realized using either 4um
SOI rib or SOI nanowire boards. For the realization of these devices, flip-chip compatible non-linear SOAs and
evanescent PIN detectors have been designed and fabricated. These active components are integrated on the SOI boards
using high precision flip-chip mounting and heterogeneous InP-to-silicon integration techniques. This type of scalable
and cost-effective silicon-based component fabrication opens up the possibility for the realization of chip-scale, power
efficient, Tb/s capacity photonic routers.
The UK silicon photonics project
Author(s):
G. T. Reed;
N. Wright;
G. Z. Mashanovich;
B. Timotijevic;
T. F. Krauss;
T. P. White;
L. O'Faolain;
R. W. Kelsall;
L. Lever;
Z. Ikonic;
A. Valvanis;
D. Leadley;
E. Findlayson;
R. M. Jenkins
Show Abstract
The project is a consortium based activity involving researchers from the UK institutions of the
Universities of Surrey, St. Andrews, Leeds, Warwick, and Southampton, as well as the commercial
research institution QinetiQ. The aims of the project are to progress the state of the art in Silicon
Photonics, in the areas of waveguides, modulators, couplers, detectors, Raman processes, and integration
with electronics. Thus the field is vast, and impossible to cover comprehensively in one project, nor
indeed in one paper. The programme is run on a truly collaborative basis, with members from each
institution running one or more work packages within the project, each co-ordinating work from their
own plus other institutions. To date, the most well developed work has emerged from the activity on basic
waveguides and their characteristics, the modulator activity, optical filters, and work on Raman
Amplifiers. This work will be the main focus of this paper, but an attempt will be made to update the
audience on the remaining activities within the project. By the nature of the project, much of the work is
medium term, and hence some activities are not expected to yield viable results until at least next year,
hence the concentration on some activities rather than all activities at this stage.
Real-time label-free biosensing with integrated planar waveguide ring resonators
Author(s):
Hans Sohlström;
Kristinn B. Gylfason;
Daniel Hill
Show Abstract
We review the use of planar integrated optical waveguide ring resonators for label free bio-sensing and present recent
results from two European biosensor collaborations: SABIO and InTopSens. Planar waveguide ring resonators are
attractive for label-free biosensing due to their small footprint, high Q-factors, and compatibility with on-chip optics and
microfluidics. This enables integrated sensor arrays for compact labs-on-chip. One application of label-free sensor arrays
is for point-of-care medical diagnostics. Bringing such powerful tools to the single medical practitioner is an important
step towards personalized medicine, but requires addressing a number of issues: improving limit of detection, managing
the influence of temperature, parallelization of the measurement for higher throughput and on-chip referencing, efficient
light-coupling strategies to simplify alignment, and packaging of the optical chip and integration with microfluidics.
From the SABIO project we report refractive index measurement and label-free biosensing in an 8-channel slotwaveguide
ring resonator sensor array, within a compact cartridge with integrated microfluidics. The sensors show a
volume sensing detection limit of 5 x 10-6 RIU and a surface sensing detection limit of 0.9 pg/mm2. From the InTopSens
project we report early results on silicon-on-insulator racetrack resonators.
Silicon waveguide-based mode-evolution polarization rotator
Author(s):
Jing Zhang;
Mingbin Yu;
Guoqiang Lo;
Dim-Lee Kwong
Show Abstract
Mode-evolution-based polarization rotators in silicon waveguides were studied. The rotator's performance
was studied under normal and abnormal launching conditions. The rotator with minimum length of 40μm was
demonstrated to provide the polarization rotation with polarization extinction ratio of 15dB at abnormal launching
condition. The insertion loss at the transition region was less than 1dB.
Design, simulation, and fabrication of a 90° SOI optical hybrid based on the self-imaging principle
Author(s):
Sawsan Abdul-Majid;
Imad I. Hasan;
Przemek J. Bock;
Trevor J. Hall
Show Abstract
This paper introduces a compact 90º optical hybrid, built on small size SOI waveguide technology .This optical hybrid
is a critical component of a potentially low-cost coherent optical receiver design developed within the frame of our
Optical Coherent Transmission for Access Network Extensions (OCTANE) project. In previous recent work, 90º
optical hybrids were realized in SOI rib waveguide technology with 4 μm top silicon and a rib height of approximately
2 μm. In this paper, we introduce a compact 90º optical hybrid, built on small size SOI waveguide technology (1.5 μm
SOI -based rib waveguide, with 0.8μm rib height). The proposed device consists of multimode interferometers (MMIs)
connected in such a way that four different vector additions of a reference signal (local oscillator) and the signal to be
detected are obtained. At the outputs, the hybrid provides four linear combination of the signal with the reference
which differs by a relative phase shift of the reference of 90º. The four output signals are detected by a pair of
balanced receivers to provide in-phase and quadrature (I&Q) channels. The phase differences arise naturally from the
self imaging property of a MMI.
The key elements of the 90º optical hybrid, including a 2×2 MMI, a 4×4 MMI, and polarization diversity
configuration have been designed and simulated, using the numerical mode solving tool FIMMPROB. The 2×2 and
4×4 MMI had overall lengths of 701μm and 3712.5μm lengths respectively. Tapers are used to couple adiabatically
single mode waveguides to the entrance and exit ports of the MMI to assure correct operation by avoiding coupling to
the higher order transverse modes allowed at the entrance and exit ports of the MMI. The simulation results at 1550nm
show polarization independence and phase errors between the ports of less than 0.03 degrees. Currently the design is
in fabrication at the Canadian Photonics Fabrication Center with the support of CMC Microsystems and experimental
results will be subject to a further report.
Highly integrated optical 8x8 lambda-router in silicon-on-insulator technology: comparison between the ring and racetrack configuration
Author(s):
G. F. Fan;
R. Orobtchouk;
J. M. Fédéli
Show Abstract
In this paper, we demonstrate a compact 8x8 λ-router using multimode-interference (MMI) crossing based on the
microring resonator. The 8x8 λ-router was designed and fabricated with a CMOS compatible silicon on insulator
technology. MMI is used to reduce the cross talk and the crossing losses of the device. Microrings with a nominal radius
of 2.5 μm and small variations of 10 nm of the nominal value allow respectively a free spectral range of 32 nm and
spacing between channels of 4 nm. The experimental results are in good agreement with the modeling. The basic add
drop filters of the devices exhibit losses of -2 dB and on/off contrast of the resonance of 20 dB. The total losses for one
channel are about -4 dB and the imbalance between the 8 channels is lower than 2 dB.
Characterisation of slab waveguides, fabricated in CaF2 and Er-doped tungsten-tellurite glass by MeV energy N+ ion implantation, using spectroscopic ellipsometry and m-line spectroscopy
Author(s):
I. Bányász;
S. Berneschi;
T. Lohner;
M. Fried;
P. Petrik;
N. Q. Khanh;
Z. Zolnai;
A. Watterich;
M. Bettinelli;
M. Brenci;
G. Nunzi-Conti;
S. Pelli;
G. C. Righini;
A. Speghini
Show Abstract
Slab waveguides were fabricated in Er-doped tungsten-tellurite glass and CaF2 crystal samples via ion implantation.
Waveguides were fabricated by implantation of MeV energy N+ ions at the Van de Graaff accelerator of the Research
Institute for Particle and Nuclear Physics, Budapest, Hungary. Part of the samples was annealed. Implantations were
carried out at energies of 1.5 MeV (tungsten-tellurite glass) and 3.5 MeV (CaF2). The implanted doses were between 5 x
1012 and 8 x 1016 ions/cm2. Refractive index profile of the waveguides was measured using SOPRA ES4G and Woollam
M-2000DI spectroscopic ellipsometers at the Research Institute for Technical Physics and Materials Science, Budapest.
Functionality of the waveguides was tested using a home-made instrument (COMPASSO), based on m-line spectroscopy
and prism coupling technique, which was developed at the Materials and Photonics Devices Laboratory (MDF Lab.) of
the Institute of Applied Physics in Sesto Fiorentino, Italy. Results of both types of measurements were compared to
depth distributions of nuclear damage in the samples, calculated by SRIM 2007 code. Thicknesses of the guiding layer
and of the implanted barrier obtained by spectroscopic ellipsometry correspond well to SRIM simulations. Irradiationinduced
refractive index modulation saturated around a dose of 8 x 1016 ions/cm2
in tungsten-tellurite glass. Annealing of
the implanted waveguides resulted in a reduction of the propagation loss, but also reduced the number of supported
guiding modes at the lower doses. We report on the first working waveguides fabricated in an alkali earth halide crystal
implanted by MeV energy medium-mass ions.
Light emission of 2D photonic crystal based on nanocrystal-Si/SiO2 superlattice structure
Author(s):
M. B. Yu;
L. Ding;
Fang-Fang Ren;
G. Q. Lo;
D. L. Kwong
Show Abstract
Because of the its indirect bandgap structure, it is a huge challenge to establish an efficient Si light emitting diode (LED) compatible with complementary metal-oxide-semiconductor (CMOS) process. In this paper, we provide an alternative
route to overcome this difficulty based on the unique property of photonic crystals (PhC). A vertical-current-injection
LED based on three-dimensional-confined structures with triangular-lattice air-hole PhC patterns has been fabricated
with enhanced light extraction from the active region (i.e., silicon-rich-oxide/SiO2 multilayer stack). The intensity and
profile of photoluminescence (PL) and electroluminescence (EL) has been found to be efficiently modulated by
controlling the optical modes of the periodic arrays via varying their structural parameters. It provides a convenient way
of redistributing the light energy in desired form and orientation. With optimized lattice constant/radius ratio, significant
enhancement up to ~7 times in both PL and EL emissions can be obtained. The mechanisms for different enhancement
features have also been theoretically analyzed based on coherent scattering and quantum electrodynamics effects, which
is well consistent with the experiment observation.
Silicon nanocrystals light-emitting devices: characterization and coupling to SU-8 waveguides
Author(s):
David Izquierdo;
María C. Garralaga;
Iñigo Salinas;
Jorge Barreto;
Carlos Domínguez;
Ignacio Garcés
Show Abstract
Silicon-based light emitting device is the missing piece in the design of complete optoelectronic circuits on silicon. A
complete electrical and optical characterization of electroluminescent silicon-nanocrystals based devices is presented.
This characterization is the first step in the design of coupling structures with optimal injection of light into optical
waveguides, which will allow the development of all-silicon photonic circuits.
In this paper, a novel coupling structure based on rectangular surface grating has been studied with promising results,
increasing the coupling efficiency to SU-8 waveguides up to 25 times. The SU-8 photoresist is fully compatible with
silicon technology and can be used to define waveguides as well as microfluidics channels. These properties are
interesting for the final application of the present study, which is to obtain a Lab-on-a-chip device, integrating all the
optical elements, control electronics and microfluidics channels.
Blue and red electroluminescence of silicon-rich oxide light emitting capacitors
Author(s):
A. Morales-Sánchez;
M. Aceves-Mijares;
A. A. González-Fernández;
K. Monfil-Leyva;
J. Juvert;
C. Domínguez-Horna
Show Abstract
Electroluminescent properties of thin silicon-rich oxide (SRO) films deposited by low pressure chemical vapor
deposition (LPCVD) were studied. The gas flow ratio Ro = N2O/SiH4 was changed to obtain different silicon
concentrations within the SRO films. After deposition, SRO films were thermally annealed at 1100ºC for 3h in N2
atmosphere in order to create silicon nanoparticles (Si-nps). Simple capacitive structures like Polysilicon/SRO/n-Si were
used for the study. These light emitting capacitors (LECs) show intense blue (~466) and red EL (~685) at room
temperature depending on the silicon excess within the SRO films. Electroluminescence in these LECs is obtained at
direct current (DC) at both forward and reverse bias conditions. Nevertheless, a stronger whole area EL is obtained when
devices are forwardly biased.
Hetero-epitaxial indium phosphide on silicon
Author(s):
C. Junesand;
W. Metaferia;
F. Olsson;
M. Avella;
J. Jimenez;
G. Pozina;
L. Hultman;
S. Lourdudoss
Show Abstract
There is an intense interest on integration of III-V materials on silicon and silicon-on-insulator for realisation of optical
interconnects, optical networking, imaging and disposable photonics for medical applications. Advances in photonic
materials, structures and technologies are the main ingredients of this pursuit. We investigate nano epitaxial lateral
overgrowth (NELOG) of InP material from the nano openings on a seed layer on the silicon wafer, by hydride vapour
phase epitaxy (HVPE). The grown layers were analysed by cathodoluminescence (CL) in situ a scanning electron
microscope, time-resolved photoluminescence (TR-PL), and atomic force microscope (AFM). The quality of the layers
depends on the growth parameters such as the V/III ratio, growth temperature, and layer thickness. CL measurements
reveal that the dislocation density can be as low as 2 - 3·107 cm-2 for a layer thickness of ~6 μm. For comparison, the
seed layer had a dislocation density of ~1·109 cm-2. Since the dislocation density estimated on theoretical grounds from
TRPL measurements is of the same order of magnitude both for NELOG InP on Si and on InP substrate, the dislocation
generation appears to be process related or coalescence related. Pertinent issues for improving the quality of the grown
InP on silicon are avoiding damage in the openings due to plasma etching, pattern design to facilitate coalescence with
minimum defects and choice of mask material compatible with InP to reduce thermal mismatch.
Cu/p-Si Schottky photodetectors at 1.55 um
Author(s):
M. Casalino;
M. Gioffrè;
G. Coppola;
M. Iodice;
L. Moretti;
I. Rendina;
L. Sirleto
Show Abstract
In this paper the realization and the characterization of a resonant cavity enhanced photodetector (RCE), completely
silicon compatible and working at 1.55 micron, is reported. The detector is a RCE structure incorporating a Schottky
diode and its working principle is based on the internal photoemission effect. In order to obtain a fabrication process
completely compatible with standard CMOS silicon technology, a photodetector having copper (Cu) as Schottky metal
has been realized. Performances devices in terms of responsivity, free spectral range, finesse are reported.
Hybrid integration of InP photodetectors with SOI waveguides using thermocompression bonding
Author(s):
Mikko Harjanne;
Markku Kapulainen;
Sami Ylinen;
Timo Aalto;
Jyrki Ollila;
Ludwig Mörl;
Wolfgang Passenberg
Show Abstract
In this paper we present the integration of an InP-based photodetector with silicon-on-insulator (SOI) waveguides using
thermocompression bonding. A BCB prism integrated on top of the light-sensitive area of a planar detector (PD) chip
deflects the light from a 4 μm thick SOI waveguide upward into the flip-chip bonded PD. A trench is etched in front of
the SOI waveguide to accommodate prisms with apexes up to 7 μm. Using thermocompression bonding between thin
gold pads (~500 nm thickness) deposited on both, SOI and photodetector chips an excellent vertical alignment accuracy
of ±100 nm can be achieved, limited only by etching and Au-deposition tolerances. A commercial flip-chip bonder
provides a lateral alignment accuracy also in the sub-micron range. Together with a previously developed process for
integrating lasers and SOA chips using the same technology, fully functional PICs can now be realized on the SOI
platform using thermocompression bonding.
Monolithically fabricated germanium-on-SOI photodetector and Si CMOS circuit for integrated photonic applications
Author(s):
Kah-Wee Ang;
Tsung-Yang Liow;
Ming-Bin Yu;
Qing Fang;
Junfeng Song;
Guo Qiang Lo;
Dim-Lee Kwong
Show Abstract
In this paper, we report our design and fabrication approach towards realizing a monolithic integration of Ge
photodetector and Si CMOS circuits on common SOI platform for integrated photonic applications. The approach, based
on the Ge-on-SOI technology, enables the realization of high sensitivity and low noise photodetector that is capable of
performing efficient optical-to-electrical encoding in the near-infrared wavelengths regime. When operated at a bias of
-1.0V, a vertical PIN detector achieved a lower Idark of ~0.57μA as compared to a lateral PIN detector, a value that is
below the typical ~1μA upper limit acceptable for high speed receiver design. Very high responsivity of ~0.92A/W was
obtained in both detector designs for a wavelength of 1550nm, which corresponds to a quantum efficiency of ~73%.
Impulse response measurements showed that a vertical PIN photodetector gives rise to a smaller FWHM of ~24.4ps,
which corresponds to a -3dB bandwidth of ~11.3GHz where RC time delay is known to be the dominant factor limiting
the speed performance. Eye patterns (PRBS 27-1) measurement further confirms the achievement of high speed and low
noise photodetection at a bit-rate of 8.5Gb/s. In addition, we evaluate the DC characteristics of the monolithically
fabricated Si CMOS inverter circuit. Excellent transfer and output characteristics were achieved by the integrated CMOS
inverter circuits in addition to the well behaved logic functions. We also assess the impact of the additional thermal
budget introduced by the Ge epitaxy growth on the threshold voltage variation of the short channel CMOS transistors
and discuss the issues and potential for the seamless integration of electronic and photonic integrated circuits.
PIN photodiodes with significantly improved responsivities implemented in a 0.35µm CMOS/BiCMOS technology
Author(s):
I. Jonak-Auer;
A. Marchlewski;
S. Jessenig;
A. Polzer;
W. Gaberl;
A. Schmiderer;
E. Wachmann;
H. Zimmermann
Show Abstract
We report on monolithically integrated PIN photodiodes whose responsivity values could be significantly enhanced over
the whole spectral range by the implementation of a Bottom Antireflective Coating (BARC) process module into
austriamicrosystems 0.35μm CMOS as well as high-speed SiGe BiCMOS technologies. The resulting photodiodes
achieve excellent responsivities together with low capacitances and high bandwidths. We processed finger-photodiodes
with interdigitated n+ cathodes, which are especially sensitive at low wavelengths, and photodiodes with full area n+
cathodes on very lightly p-doped start material. We present a method of depositing an antireflective layer directly upon
the Si surface of the photodiode by changing the standard process flow as little as possible. With just one additional mask
alignment and a well controlled etch procedure we manage to remove the thick intermetal oxide and passivation nitride
stack over the photodiodes completely without damaging the Si surface. The following deposition of a CVD Silicon
Nitride BARC layer not only minimizes the reflected fraction of the optical power but also acts as passivation layer for
the photodiodes. Another benefit of BARC processing is the fact that in-wafer and wafer-to-wafer quantum efficiency
variations can be dramatically reduced. In our experiments we deposited BARC layers of different thicknesses that were
optimised for violet, red and infrared light. Responsivity measurements resulted in values as high as R=0.27A/W at
λ=410nm, R=0.53A/W at λ=670nm and R=0.5A/W at λ=840nm.
Integrated streak camera in standard (Bi)CMOS technology
Author(s):
Wilfried Uhring;
Jean-Pierre Le Normand;
Virginie Zint;
Martin Zlatanski
Show Abstract
The conventional streak camera (CSC) is an optoelectronic instrument which captures the spatial distribution versus time
of a ultra high-speed luminous phenomena with a picosecond temporal resolution and a typical spatial resolution of
60 μm. This paper presents two Integrated Streak Camera (ISC) architectures called MISC (M for Matrix) and VISC (V
for Vector) which replicate the functionality of a streak camera on a single CMOS chip.
The MISC structure consists of a pixel array, where the column depth together with the sampling rate determine the
observation window. For proper operation, the image of the slit has to be spread uniformly over the rows of the imager.
The VISC architecture is based on a single column of photosensors, where each element is coupled to a front-end and a
multi-sampling and storage unit. The observation window is determined by the sampling rate and the depth of the
memory frame. The measurement of a 6 ns FWHM 532 nm light pulse laser is reported for both ISCs. For the two
architectures, the spatial resolution is linked to the size and the number of the photodetectors.
Silicon-based ultra-wide discrete band conversion
Author(s):
Ozdal Boyraz;
En-Kuang Tien;
Shiming Gao
Show Abstract
Nonlinear silicon photonics has been an immense research subject in the past several years with promising prospects of
delivering chip scale signal modulation, shaping and characterization tools. In particular, broadband parametric process
has been considered for applications ranging from wideband light amplifiers to signal characterization and signal
shaping tools. Although underlying nonlinear effect, Kerr phenomena, in silicon has generated promising result of
wavelength conversion, the success of these devices have been challenged by the presence of nonlinear losses such as
two photon absorption and the two photon generated free carrier absorption. Experimental demonstrations were limited
to conversion efficiencies below -10dB. Here, we present the prospect of ultra wide discrete band conversion schemes
and the prospect of parametric process at mid-infrared wavelengths where nonlinear losses are not present. In particular,
we explore the parametric wavelength conversion scheme at mid-wave infrared wavelength (2μm~6μm) by four-wavefixing
process in silicon waveguides with new cladding materials, such as sapphire, that can provide transparency up to
6μm and facilitate phase matching condition for discrete wavelength bands as far as 60THz away from each other.
Design criteria include the optimization of mode overlap integrals and dispersion engineering for an ultra-wide band
signals. The particular results of wavelength conversion between 2μm bands and 5μm bands, and between 1.8μm bands
and >4μm bands will be presented. Prospects of frequency band conversion in generation of new infrared signals and
low noise, room temperature detection of mid-infrared signals will also be discussed.
Terahertz-range stimulated emission due to electronic nonlinear frequency conversion in silicon
Author(s):
Sergey G. Pavlov;
Heinz-Wilhelm Hübers;
Ute Böttger;
Rene Eichholz;
Valery N. Shastin;
Nikolay V. Abrosimov;
Helge Riemann;
Hans-Joachim Pohl;
Britta Redlich
Show Abstract
Silicon-based semiconductors offer optically low-loss and high-thermal-conducting lattice for the broad-band terahertz
active media that can be used in the range of 5-7 THz. We report on realization of the terahertz-range stimulated
emission from monocrystalline natural and isotopically enriched silicon crystals doped by group-V donor centers due to
nonlinear frequency conversion. Lasing in the frequency bands of 1.2 - 1.8 THz; 2.5 - 3.4 THz has been achieved from
silicon crystals doped by phosphorus and in the frequency band of 4.6 - 6.4 THz from different donors under optical
pumping by radiation of mid-infrared free electron laser at cryogenic temperatures. Analysis of the data shows that the
emission in high-frequency band corresponds to electronic Stokes-shifted Raman-type lasing. The low-frequency bands
indicate on high-order nonlinear frequency conversion processes similar to four-wave mixing accompanied by highenergy
intervalley g-phonons and f-phonons of host lattice. These lasers supplement terahertz silicon lasers operating on
transitions between donor states.
Enhancing the efficiency of silicon Raman converters
Author(s):
Nathalie Vermeulen;
John E. Sipe;
Hugo Thienpont
Show Abstract
We propose a silicon ring Raman converter in which the spatial variation of the Raman gain along the ring for TE
polarization is used to quasi-phase-match the CARS process. If in addition the pump, Stokes, and anti-Stokes waves
involved in the CARS interaction are resonantly enhanced by the ring structure, the Stokes-to-anti-Stokes conversion
efficiency can be increased by at least four orders of magnitude over that of one-dimensional perfectly phase-matched
silicon Raman converters, and can reach values larger than unity with relatively low input pump intensities. These
improvements in conversion performance could substantially expand the practical applicability of the CARS process for
optical wavelength conversion.
Strain dependence of second-harmonic generation in silicon
Author(s):
Clemens Schriever;
Christian Bohley;
Jörg Schilling;
Ralf B. Wehrspohn
Show Abstract
Strained silicon is a versatile new type of material, which has found application in microelectronics and integrated
optics. The applied strain alters the electronic and optical properties and gives rise to new properties previously
not known to exist in silicon, like a bulk second order nonlinear susceptibility. Here, we determine experimentally
the strain dependence of the second order nonlinear susceptibility on the applied strain. To this purpose, the
strain induced second harmonic signal generated in the silicon was measured in a reflection geometry with
azimuthal angle dependence. The extracted components of the second order nonlinear susceptibility were
determined and compared to the unstrained case. Additionally the measurements were compared to results
obtained with an analytical model, that takes into account the exponential strain decay at the sample surface.
The predicted linear dependence between the surface strain and the second order nonlinear susceptibility agrees
well with the results of our experimental work.
Hybrid silicon-organic racetrack resonator designs for electro-optical modulation
Author(s):
Jan Hampe;
Jan Hendrik Wülbern;
Stefan Prorok;
Alexander Yu. Petrov;
Manfred Eich;
Jingdong Luo;
Alex K.-Y. Jen
Show Abstract
Racetrack resonators based on the silicon-on-insulator platform are proposed for electro-optical modulation. The
resonators are functionalized by a cladding of a second order nonlinear optical polymer. Two different concepts for the
racetrack design employing different waveguide geometries for quasi-TE and quasi-TM polarization operation are
presented. In both resonator designs the electrical contact is established by fully etched segmented electrode sections to
allow for an easy fabrication process. For quasi-TM polarization the width of the strip waveguide is optimized to 400
nm. The Q factor of 2000 is measured for a sample with segmented electrode. A loss of 0.4 dB per segmented waveguide
is deducted. For the quasi-TE polarization the slot waveguide geometry is optimized to 470 nm total width including a
vertical slot of 90 nm width. Only the straight parts of the racetrack are slotted, while the bends are built from strip
waveguides. To convert the mode from strip to slot geometry stub like couplers of 100 nm length are employed. The
measured Q factor is 550. The in device Pockels coefficient is measured to r33 = 1 pm/V. This small value indicates a
very low poling induced polar order which needs to be improved. This is a topic of current investigation.
An optimization method for depletion-based silicon optical modulators
Author(s):
G. Rasigade;
D. Marris-Morini;
L. Vivien;
E. Cassan
Show Abstract
A new optimization method is described and performed on high-speed silicon optical modulators based on carrier
depletion in a p-i-n junction. Quantitative results on the geometry of the waveguide and doping concentrations of the pand
n-doped regions are presented at the end of the optimization. General rules can thus be applied to design high
performances optical modulators in term of modulation efficiency and insertion loss. Complete electro-optical
simulations have been performed on optimal designs to evaluate the corresponding Figures of Merit and theoretical
limits on performances have been exhibited. VπLπ as low as 1.25 V.cm has been obtained at best for the p-n
configuration, for a bias of 5 V and for a rib height of 400 nm. A strong dependence of the total optical loss with the
geometry of the waveguide has also been demonstrated with an optimal value of 3 dB.
Tunable silicon CROW delay lines
Author(s):
Francesco Morichetti;
Antonio Canciamilla;
Matteo Torregiani;
Carlo Ferrari;
Andrea Melloni;
Mario Martinelli
Show Abstract
Tunable coupled resonator optical waveguides (CROWs) are powerful and versatile devices that can be used to
dynamically control the delay of optical data streams on chip. In this contribution we show that CROW delay
lines fabricated on a silicon on insulator (SOI) platform are suitable for applications in the emerging scenario of
optical systems at 100 Gbit/s. Issues concerning technology, design, limits and applications of SOI CROWs are
discussed. The performances of silicon CROW delay lines activated by thermal tuning are compared to those
of glass CROW in terms of power consumption, thermal crosstalk and reconfiguration speed. The continuous
delay of 10-ps long optical pulses by 8 bit length is demonstrated by using a silicon CROW with a bandwidth
of 87 GHz and made of 12 RRs. At 100 Gbit/s this structure provides comparable figures of merit (fractional
delay of 0.75 bit/RR and fractional loss of 0.7 dB per bit-delay) of state-of-the art glass CROW operating at
10 Gbit/s, yet the area of the latter being three order of magnitude larger. The compatibility of silicon CROW
with the emerging 100 Gbit/s systems is demonstrated by showing error-free phase-preserving propagation of
a 100 Gbit/s return-to-zero (RZ) polarization-division-multiplexing (PolDM) differential quaternary phase shit
keying (DQPSK) signal dynamically delayed by the CROW. It is also demonstrated that a silicon CROW can
be used in a PolDM system to introduce a polarization selective delay in order to optimize the time interleaving
of the two orthogonally polarized data streams.
RF frequency transparent 90° hybrid based on silicon on insulator photonic circuit
Author(s):
Rakesh Sambaraju;
Jose Vicente Galan-Conejos;
Javier Herrera;
Amadeu Griol;
Claudio Otón;
Pablo Sanchis;
Alejandro Martínez
Show Abstract
A simple configuration for achieving a radio frequency transparent 90° hybrid, for broadband QAM wireless systems
using silicon photonics is proposed. The device consists of a high Q ring resonator which induces an optical 90° phase
shift between two adjacent resonant wavelengths. When these optical carriers are modulated by an RF carrier the
resulting device behaves as an RF 90° hybrid. Numerical simulations of the phase shift were performed on a 40 GHz
carrier, and to demonstrate the frequency transparency phase shift simulations was also performed at a carrier frequency
of 60 GHz. One of the main applications of such a device is the generation of millimeter wave 10 Gb/s wireless based on
quadrature amplitude modulation.
Cycle-accurate evaluation of reconfigurable photonic networks-on-chip
Author(s):
Christof Debaes;
Iñigo Artundo;
Wim Heirman;
Jan Van Campenhout;
Hugo Thienpont
Show Abstract
There is little doubt that the most important limiting factors of the performance of next-generation Chip Multiprocessors
(CMPs) will be the power efficiency and the available communication speed between cores. Photonic
Networks-on-Chip (NoCs) have been suggested as a viable route to relieve the off- and on-chip interconnection
bottleneck. Low-loss integrated optical waveguides can transport very high-speed data signals over longer
distances as compared to on-chip electrical signaling. In addition, with the development of silicon microrings,
photonic switches can be integrated to route signals in a data-transparent way. Although several photonic NoC
proposals exist, their use is often limited to the communication of large data messages due to a relatively long
set-up time of the photonic channels. In this work, we evaluate a reconfigurable photonic NoC in which the
topology is adapted automatically (on a microsecond scale) to the evolving traffic situation by use of silicon microrings.
To evaluate this system's performance, the proposed architecture has been implemented in a detailed
full-system cycle-accurate simulator which is capable of generating realistic workloads and traffic patterns. In
addition, a model was developed to estimate the power consumption of the full interconnection network which
was compared with other photonic and electrical NoC solutions. We find that our proposed network architecture
significantly lowers the average memory access latency (35% reduction) while only generating a modest increase
in power consumption (20%), compared to a conventional concentrated mesh electrical signaling approach. When
comparing our solution to high-speed circuit-switched photonic NoCs, long photonic channel set-up times can
be tolerated which makes our approach directly applicable to current shared-memory CMPs.
High-speed optoelectronic IC for multi-standards of optical storage system
Author(s):
Sanghyun Cha;
Hawoong Jeong;
Chaedong Go;
Deukhee Park;
Changseok Lee;
Kyoungsoo Kwon;
Jeashin Lee
Show Abstract
The conventional scheme of optical pick-up unit (OPU) should require two or three optoelectronic integrated circuits
(OEICs) to cover triple-wavelength λ =780nm, 650nm and 405nm). In order to reduce cost and waste of resources, onechip
solution of the OEIC is required. In this paper, the OEIC is designed which can cover triple-wavelength and three
optical storage standards which are compact disk (CD), digital versatile disk (DVD) and Blue-Ray. The OEIC has dualarrays
of photodiodes because focus of laser is varied depending on wavelength. One of arrays senses the laser of
λ =780nm and another senses the lasers of λ =650nm and λ =405nm. For low power consumption and small die area, one
wideband transimpedance amplifier (TIA) is used for two photodiodes which are for CD and DVD or Blue-Ray,
respectively. And two small size switches are included to select photodiodes. The PIN fingerdiode with N+ fingercathode
is integrated to guarantee high performances for λ =405nm and 650nm. And the isolation area between adjacent
photodiodes is made by floated P+ implant for reducing power-loss. The measured cutoff bandwidth of the OEIC is
210MHz for λ =405nm. The OEIC is fabricated in a 0.6- μm BiCMOS technology and dissipates 150mW for a single
supply voltage of 5V. The active area is 1.4x1.2mm2.
320 Gbps monolithic silicon photonic DWDM receiver
Author(s):
Qing Fang;
Tsung-Yang Liow;
Kah Wee Ang;
Yu Ting Phang;
Ming Bin Yu;
Guo Qiang Lo;
Dim-Lee Kwong
Show Abstract
In this paper, we presented a high performance monolithic Si DWDM receiver comprising a 1×32 Si-based AWG filter
and a high speed waveguided Ge-on-Si photodetectors array on silicon-on-insulator platform. The Si-based AWG has
200 GHz channel spacing and its optical adjacent crosstalk performance is more than 18 dB. Each Ge-on-Si
photodetector has 10 GHz bandwidth; and can transmit at least 10 Gbps data rate. So, the aggregated data rate of the
DWDM receiver is at least 320 GHz. At a BER of 1 × 10-11, the DWDM receiver showed an optical input sensitivity
between -16 dBm and -19 dBm for all 32 channels in Lband. This first demonstration indicates the feasibility and
potential of manufacturing low cost silicon DWDM receivers for terabit data communications. The size of entire receiver
is 1.5×1.0 mm2.
Rigorous characterization of silicon nanowire for compact nanophotonic devices
Author(s):
B. M. A. Rahman;
D. M. H. Leung;
K. Namassivayane;
A. Agrawal;
M. Ashraf;
H. Tanvir;
K. T. V. Grattan
Show Abstract
When the cross-section of an optical waveguide is much smaller than the operating wavelength, unique materials and
structural dependent properties can be observed. In this regard silicon has been particularly attractive as the low-cost and
mature CMOS fabrication technology widely used in the electronics industry can be exploited. The high index contrast
of silicon allows light confinement in submicron size waveguides, along with the creation of very compact bends, to
allow increased functionality of photonic integrated circuits. A rigorously H-field based vectorial modal analysis has
been carried out, which can more accurately characterize the abrupt dielectric discontinuity of a high index contrast
optical waveguide. As a result, the full-vectorial H and E-field and the Poynting vector profiles are shown in detail. The
work done and reported reveals that the mode profile of a circular silicon nanowire is not circular and also has a strong
axial field component. Arising from the results of the analysis, the characteristics of single mode operation, the vector
field profiles, the modal ellipticity and the group velocity dispersion of this silicon nanowire both circular and planar are
presented. The modal hybridness and birefringence of rectangular silicon nanowires and slot-type waveguides are also
presented.
Low voltage, moderate rejection ratio electro-optic modulator at 2.2µm obtained by proton exchange in lithium niobate
Author(s):
Olga Caballero-Calero;
Romain Burla;
Thibaut Moulin;
Alain Delboulbé;
Laurent Jocou;
Jean-Philippe Berger;
Guillermo Martin
Show Abstract
In this paper we present the performances of a modulator, realized by proton exchange, achieving a moderate rejection
ratio in the K-band (2.2μm). The device consists on a simple Mach-Zehnder beam combiner, developed by our partners
from Photline Technologies®, pushing forward their proton exchange technique in order to achieve single mode optical
guiding above 1.9μm in Lithium Niobate X-cut substrates. Applying low modulation voltages (Vπ=3.4V), and by a Fast
Fourier Transform obtain the spectrum of the source with a moderate resolution, due to the reduced length of the active
part (32mm). A white light interferometer is also shown, using a band-pass filter, from 1.8 to 2.6μm.
Tunable integrated optical filters based on sapphire microspheres and liquid crystals
Author(s):
Giovanni Gilardi;
Hasan Yilmaz;
Mohammed Sharif Murib;
Rita Asquini;
Antonio d'Alessandro;
Ali Serpengüzel;
Romeo Beccherelli
Show Abstract
We present an integrated optical narrowband electrically tunable filter based on the whispering gallery modes of sapphire
microspheres and double ion-exchanged channel BK7 glass waveguides. Tuning is provided by a liquid crystal infiltrated
between the spheres and the glass substrate. By suitably choosing the radii of the spheres and of the circular apertures,
upon which the spheres are positioned, arrays of different filters can be realized on the same substrate with a low cost
industrial process. We evaluate the performance in terms of quality factor, mode spacing, and tuning range by comparing
the numerical results obtained by the numerical finite element modeling approach and with the analytical approach of the
Generalized Lorenz-Mie Theory for various design parameters. By reorienting the LC in an external electrical field, we
demonstrate the tuning of the spectral response of the sapphire microsphere based filter. We find that the value of the
mode spacing remains nearly unchanged for the different values of the applied electric field. An increase of the applied
electric field strength, changes the refractive index of the liquid crystal, so that for a fixed geometry the mode spacing remains unchanged.
Electrically driven hybrid Si/III-V lasers based on adiabatic mode transformers
Author(s):
B. Ben Bakir;
N. Olivier;
Ph. Grosse;
S. Messaoudène;
S. Brision;
E. Augendre;
P. Philippe;
K. Gilbert;
D. Bordel;
J. Harduin;
J.-M. Fedeli
Show Abstract
We report the first Silicon/III-V evanescent laser based on adiabatic mode transformers. The hybrid structure is formed
by two vertically superimposed waveguides separated by a 100nm-thick SiO2 layer. The top waveguide, fabricated in an
InP/InGaAsP-based heterostructure, serves to provide optical gain, and the bottom Si-waveguides system, which
supports all optical functions, is constituted by two tapered rib-waveguides (mode transformers), two distributed Bragg
reflectors (DBR), and a surface-grating coupler. The supermode of this hybrid structure is controlled by an appropriate
design of the tapers located at the edges of the gain region. In the middle part of the devices, almost all the field resides
in the III-V waveguide so that the optical mode experiences maximal gain, while in regions near the III-V facets, mode
transformers ensure an efficient transfer of the power flow towards Si-waveguides. The investigated device operates
under quasi-continuous wave regime. The room temperature threshold current is 100 mA, the side mode suppression
ratio is as high as 20dB, and the fiber-coupled output power is ~7mW.
Magnetic nanoparticles-doped silica layer reported on ion-exchanged glass waveguide: towards integrated magneto-optical devices
Author(s):
Hadi Amata;
François Royer;
Fadi Choueikani;
Damien Jamon;
Jean-Emmanuel Broquin;
Jean Claude Plenet;
Jean Jaques Rousseau
Show Abstract
In the framework of optical telecommunication systems, many functions are integrated on the same substrate.
Nevertheless, one of the most important, such as isolation, is achieved using discrete components. It is based on
magnetic materials which are always difficult to integrate with classical technologies. This is due to the annealing
temperature of magnetic materials. In this paper we present another way for the realisation of such components. We use
a dip coating process to report a magnetic nanoparticles doped silica layer on ion-exchanged glass waveguide. The
advantages of this method is discussed and we demonstrate its compatibility with ion-exchanged technology. By varying
the refractive index of the layer, we can adjust the interaction between the waveguide and the magneto-optical layer.
10Gbps monolithic silicon FTTH transceiver for PON
Author(s):
J. Zhang;
T. Y. Liow;
G. Q. Lo;
D. L. Kwong
Show Abstract
We propose a new passive optical network (PON) configuration and a novel silicon photonic transceiver architecture for optical network unit (ONU), eliminating the need
for an internal laser source in ONU. We adopt dual fiber network configuration. The internal
light source in each of the ONUs is eliminated. Instead, an extra seed laser source in the
optical line termination (OLT) operates in continuous wave mode to serve the ONUs in the
PON as a shared and centralized laser source. λ1 from OLT Tx and λ2 from the seed laser are
combined by using a WDM combiner and connected to serve the multiple ONUs through the
downstream fibers. The ONUs receive the data in λ1. Meanwhile, the ONUs encode and
transmit data in λ2, which are sent back to OLT.
The monolithic ONU transceiver contains a wavelength-division-multiplexing (WDM) filter
component, a silicon modulator and a Ge photo-detector. The WDM in ONU selectively
guides λ1 to the Ge-PD where the data in λ1 are detected and converted to electrical signals,
and λ2 to the transmitter where the light is modulated by upstream data. The modulated
optical signals in λ2 from ONUs are connected back to OLT through upstream fibers.
The monolithic ONU transceiver chip size is only 2mm by 4mm. The crosstalk between the
Tx and Rx is measured to be less than -20dB. The transceiver chip is integrated on a SFP+
transceiver board. Both Tx and Rx demonstrated data rate capabilities of up to 10Gbps. By
implementing this scheme, the ONU transceiver size can be significantly reduced and the
assembly processes will be greatly simplified. The results demonstrate the feasibility of mass
manufacturing monolithic silicon ONU transceivers via low cost
Laser-assisted chemical etching for texturing silicon surface
Author(s):
Mitsunori Saito;
Saori Kimura
Show Abstract
Alkaline etching of silicon surfaces was studied to make anisotropic microstructures. An aqueous solution of potassium
hydroxide was used as an etchant. The etching rate of silicon was heavily dependent on crystal orientation and
temperature; i.e., the etching rate for the (100) surface was four times larger than that for the (111) surface, and they both
increased by ten times as temperature rose from 25 to 60 °C. A laser beam was irradiated to a silicon surface to create a
temperature distribution that realized selective etching. A pulsed green laser (532 nm) of 5 ns duration was used as a
light source to enhance temperature difference between irradiated and nonirradiated portions. By passing through a
photomask and an imaging lens system, the laser beam created an optical power distribution on a silicon plate dipped in
an etchant. Depending upon the mask pattern, a groove array or a two-dimensional pit array was created on the silicon
surface. These pits took a rectangular shape on the silicon (100) plate, while they took a triangular or hexagonal shape on
the (111) plate.
Discretely tunable microwave photonics beamformer based on ring resonators and arrayed waveguide gratings
Author(s):
J. D. Doménech;
P. Muñoz;
J. Capmany
Show Abstract
In this paper a novel microwave photonics beamformer device concept, for single side band (SSB) 40 GHz
modulated signals, is presented. The proposed device comprises tunable lasers, flat-top arrayed waveguide
gratings (AWG), a Mach Zender Modulator (MZM), an all-pass ring resonator and photodetectors. The device
can be produced as a photonic integrated circuit. The signals from the lasers (one for each beamformer radiant
element) are multiplexed by the first AWG, modulated, and passed through the all-pass ring resonator. The AWG
channel spacing and the ring resonator Free Spectral Range (FSR) are both set to be equal to 100 GHz. The signal
is demultiplexed by a second AWG and finally photodetected. By tuning each laser within its corresponding AWG
passband, the phase difference between the optical carrier and the 40 GHz microwave modulated signal for each
beamformer element can be controlled. The difference is determined by the phase response of the all-pass ring
resonator. A critical part of the design is the alignment between the resonances of the ring resonator and both
AWGs, but this can be alleviated by using a single AWG in fold-back configuration. The power provided to each
beamformer element is different due to the intrinsic non-uniform losses of the AWGs and the ring resonators, but
this can also be solved either by properly setting the lasers power, or by means of additional optical amplifiers.
The presented analysis is independent of the integration technology. In Silicon photonics, the AWGs and ring
resonator can be produced, while the (hybrid) integration of lasers, modulator, photodetectors (and eventually
amplifiers) is a challenge. The device can be monolithically integrated on semi-insulating InP technology.
Influence of the localization of process-induced disorder on planar photonic crystal waveguide properties
Author(s):
Ran Hao;
Eric Cassan
Show Abstract
The influence on photonic crystal waveguide properties of the fabrication-induced disorder was numerically studied.
By comparing the transmission spectra obtained using 3D-FDTD for four kinds of fabrication disorders, it was
shown that disorder modifies the waveguide mode properties, especially in the slow light regime. Emphasis was put
on the influence of the disorder localization. Results have shown the major role played by technological fluctuations
of the size, shape, and position of the two first rows of holes along PhC waveguide axis. Results have revealed that
bandgap properties remain almost unaffected even for huge disorder levels provided that the two first rows of holes
remain unchanged. Interestingly, 3D-simulation have also shown that sharp transmission spectrum cutoffs that
characteristize slow wave modes in the two-dimensional PhC bandgap are then not suppressed by the introduction of
disorder but are only blue-shifted. This point constitutes an interesting result for optical integrated devices relying on
low group velocity phenomena.
Study on the diffraction performance of the etched blazed grating
Author(s):
Shuping Li;
Xiangdiao Deng;
Jingping Zhu
Show Abstract
The diffraction properties of a silica-based etched diffraction grating are investigated by numerical simulation in threedimension.
The field distribution of the electromagnetic filed in the near and far away groove area, the diffraction
efficiency and spectral response of 8 channels are analyzed respectively. The numerical results show that the diffraction
angle is not satisfied the famous grating formula, the deviation of the diffraction angle is increasing with the diffraction
order. And when the groove depth is in the low and medium modulation region, the diffraction efficiency reaches over
90%, and the spectral response of an etched grating is uniform within the fiber communication spectrum range.
Digital holographic microscopy for silicon microsystems metrology
Author(s):
Yves Delacrétaz;
Christian Depeursinge
Show Abstract
We propose to use digital holographic microscopy (DHM) with an illumination in the near infrared spectrum
bandwidth, where the silicon is known to have small absorption. With such an illumination condition, it is possible
to observe a wider range of specimens than in the visible spectrum, providing a new metrology technique for
3D silicon micro-systems characterization. Suitability of DHM with near infrared illumination for micro-optical
elements and wafer inspection is demonstrated. The intrinsic robustness and speed of the method place DHM
as a valuable candidate for real-time quality check inside production chains, opening a wide field of applications
in quality control.
A 10Gb/s transimpedance amplifier for hybrid integration of a Ge PIN waveguide photodiode
Author(s):
A. Polzer;
W. Gaberl;
R. Swoboda;
H. Zimmermann;
J.-M. Fedeli;
L. Vivien
Show Abstract
The presented paper describes a 10 Gbps optical receiver. The transimpedance amplifier (TIA) is realized in standard
0.35 μm SiGe BiCMOS technology. The main novelty of the presented design - investigated in the European
Community project HELIOS - is the hybrid connection of the optical detector. The used Germanium photodetector will
be directly mounted onto the receiver.
A model of the relevant parasitics of the photodetector itself and the novel connection elements (micropads, metal vias
and metal lines) is described. Based on this photodetector model an optical receiver circuit was optimized for maximum
sensitivity at data rates in the range of 10 Gbps.
The design combines a TIA and two limiting amplifier stages followed by a 50 Ω CML-style logic-level output driver.
To minimize power supply noise and substrate noise, a fully differential design is used. A dummy TIA provides a
symmetrical input signal reference and a control loop is used to compensate the offset levels. The TIA is built around a
common-emitter stage and features a feedback resistor of 4.2 Ω. The total transimpedance of the complete receiver
chain is in the range of 275 kΩ. The value of the active feedback resistor can be reduced via an external control voltage
to adapt the design to different overall gain requirements. The two limiting amplifier stages are realized as differential
amplifiers with voltage followers. The output buffer is implemented with cascode differential amplifiers. The output
buffer is capable of driving a differential 50Ω output with a calculated output swing of 800mVp-p.
Simulations show an overall bandwidth of 7.2 GHz. The lower cutoff frequency is below 60 kHz. The equivalent input
noise current is 408 nA. With an estimated total photodiode responsivity of 0.5 A/W this allows a sensitivity of around -
23.1 dBm (BER = 10-9). The device operates from a single 3.3 V power supply and the TIAs and the limiting amplifier
consume 32 mA.
Low-voltage high-efficiency light emitting diodes with lateral-current injection based on truncated Si/SiO[sub]2[/sub] quantum wells
Author(s):
L. Ding;
M. B. Yu;
G. Q. Lo;
D. L. Kwong
Show Abstract
An efficient low-voltage lateral current-injection CMOS-compatible light emitting diode (LED) based on Si/SiO2
multiple quantum wells (MQW) is reported. This is the first time that a lateral current-injection LED is demonstrated
with Si/SiO2 MQW structures. Strong electroluminescence (EL) in the wavelength ranging from 450 to 850 nm can be
observed when the device is reverse-biased at the voltage of as low as ~6 V with the current of ~1 mA. With the lateral
current injection structure, the working voltage of the LED is significantly reduced because the voltage is fully applied
across the active region instead of dielectrics which cannot be avoided in vertical current-injection Si/SiO2 quantum well
LEDs that have received intensive research attention during the last decade. The external quantum efficiency is ~20
times higher than that of the conventional vertical current-injection LEDs based on Si/SiO2 MQW. The light emission
would probably originate from the impact ionization due to the hot carriers generated in ultra-thin Si film when the
device is reverse-biased. The lateral configuration provides a versatile technology platform, since many light-extraction
and mono-chromaticity enhancement techniques can be directly applied onto the top emission window.
Monolithic integration and optimization of waveguide silicon modulators and germanium photodetectors
Author(s):
Tsung-Yang Liow;
Kah-Wee Ang;
Qing Fang;
Junfeng Song;
Yong-Zhong Xiong;
Mingbin Yu;
Guo-Qiang Lo;
Dim-Lee Kwong
Show Abstract
By tapping on the volume manufacturing capability of the Si CMOS platform, Si photonics can potentially offer costeffective
yet high performance optical interface solutions, and will be especially important in short reach applications.
Numerous challenges lie ahead for monolithically integrated Si photonics. There are process integration and thermal
budget constraints when monolithically integrating individual Si photonic components such as modulators and
photodetectors, and also CMOS on the same chip. In this work, the CMOS-compatible monolithic integration of Si
modulators and Ge-on-Si photodetectors on the same wafer is demonstrated and the details of performance optimization
are also discussed. Besides process compatibility, the modulators and photodetectors should possess high efficiency and
the ability to operate at low power supply voltages. The methods to achieve this are also described. The carrier depletion
type Si modulators achieved high modulation efficiency and speed (Vπ.Lπ = 2.6 V.cm, 10 Gbps). At 10 Gbps, an
extinction ratio of 6 dB was measured in a modulator with 2-mm-long phase-shifters using single-ended drive (VRF = 5
Vpp). Low voltage operation at 3.125 Gbps was also demonstrated using differential drive, which allowed the drive
voltage to be reduced to only 1 V (VRF = 1 Vpp). Ge-on-Si photodetectors were integrated by using a selective epitaxial
Ge growth process. The performance of such photodetectors was evaluated in terms of speed, responsivity and dark
current for different temperatures and operating voltages. It is shown that introducing a low thermal budget post-epitaxy
anneal improves the performance of the Ge photodetectors, resulting in significantly improved dark current. The
responsivity and speed in the low voltage regime are also enhanced, which enhances low voltage or even short-circuit
(VBias = 0 V) operation.
Nanometer germanium photodetector with aluminum surface plasmon antenna for enhanced photo-response
Author(s):
Fang-Fang Ren;
Kah-Wee Ang;
Guo-Qiang Lo;
Dim-Lee Kwong
Show Abstract
We present theoretical design process for plasmon-enhanced photodetectors with nanometer-scale germanium area. The
nontraditional plasmonic metal aluminum is employed as the material of surface plasmon antenna instead of noble
metals owing to its integration compatibility with existing silicon complementary metal-oxide-semiconductor
technology. The electrode/antenna is patterned with shallow concentric grating surrounding a subwavelength aperture
(bull's eye structure) for concentrating and guiding strong optical intensity into an ultra-small active area. The physical
modeling and geometric parameters optimization are performed based on the finite-difference time-domain method. Due
to the excitation of fundamental or 2nd-order Bloch surface plasmon polaritons, high absorption can be obtained at nearinfrared
wavelengths of 1310 and 800 nm.
One theoretical analysis about the two resonators system
Author(s):
G. F. Fan;
R. Orobtchouk
Show Abstract
We present one theoretical analysis about the two resonators system. The model shows good agreement with other theoretical approaches. The properties of the system have been studied using the model. We also provide the analysis about the electromagnetically induced transparency (EIT) in the two resonators system,which shows, properly designed, the system exhibits a narrow high-quality-factor(Q) EIT-like resonant mode.
Apodization of coupled resonator optical waveguide devices through a longitudinal offset technique
Author(s):
J. D. Doménech;
P. Muñoz;
J. Capmany
Show Abstract
In this paper, a novel technique to set the coupling constant between cells of a coupled resonator optical waveguide
(CROW) device, in order to tailor the filter response, is presented. It is known that using the same K value
for all the couplers produces filtering responses with significant side-lobes for the side-coupled integrated spaced
sequence of resonators (SCISSOR) or significant ripples in the pass-band for the direct coupled microrings
(CROW). It is also known that the side-lobes/ripples can be reduced, and the pass/reject bands can be made
wider, by apodizing the K value of each individual coupler in the structure, starting from a nominal K value
(either increasing or decreasing it). This technique consists on changing the effective length of the coupling
section by applying a longitudinal offset between the resonators. On the contrary, the conventional techniques
are based in the transversal change of the distance between the ring resonators, in steps that are commonly below
the current fabrication resolution step (nm scale), leading to strong restrictions in the designs. The technique has
been experimentally demonstrated employing a racetrack ring resonator geometry. The proposed longitudinal
offset technique allows a more precise control of the coupling and presents an increased robustness against the
fabrication limitations, since the needed resolution step is two orders of magnitude higher. Both techniques are
compared in terms of the transmission response of CROW devices, under finite fabrication resolution steps. The
offset technique presented is sufficient by itself for apodization, and optimized CROW's can be produced with a
fixed distance between the rings, solely by changing the offsets.
Compact integrated optical directional coupler with large cross section silicon waveguides
Author(s):
J. P. George;
N. Dasgupta;
B. K. Das
Show Abstract
Compact integrated optical directional couplers with symmetrically- and asymmetrically etched S-bend waveguides on
SOI platform have been designed, fabricated and characterized. We have found that the directional couplers with
asymmetrically etched waveguide structures can increase the device compactness to about 4 to 5 times that of the
conventional symmetrically etched bend waveguide structures without compromising much on the optical loss budgets.
The over all waveguide loss and loss per S-bend have been measured to be ~ 0.5 dB/cm and ~ 1 dB, respectively. The
directional couplers are found to be polarization dependent (up to ~ 2 dB) and nearly wavelength independent (1510 nm
< λ < 1600 nm).
Design and fabrication of a novel evanescent germanium electro-absorption (EA) modulator
Author(s):
Andy Eu-Jin Lim;
Kah Wee Ang;
Qing Fang;
Tsung-Yang Liow;
Mingbin Yu;
Guo-Qiang Lo;
Dim-Lee Kwong
Show Abstract
An electro-absorption (EA) modulator holds distinct advantages over the silicon Mach-Zehnder interferometer
(MZI) modulator by having lower energy consumption, a smaller footprint on-chip, and a potentially higher modulation
speed. These are crucial for efficient encoding of optical signals in silicon photonics circuits. Furthermore, the
development of a Group IV-based (i.e. silicon- or germanium-based) EA modulator allows compatibility with standard
complementary metal-oxide-semiconductor (CMOS) processing. In this work, we demonstrate a novel evanescent
germanium (Ge) EA modulator structure. A lateral electric field is employed in the Ge rib to enhance absorption via the
Frank-Keldysh effect. This shifts the absorption edge significantly with applied bias for wavelengths beyond 1600 nm.
A peak extinction ratio of ~15 dB at 1600 nm could be achieved for a <3 V dynamic voltage swing from a 20 μm
modulator. The impact of device dimensions and design structure on optical modulation and insertion loss are also
investigated. In addition, monolithic integration of waveguided Ge-based modulator and photodetector can be simplified
with our proposed EA modulator structure. The results from this work can make a low power and high speed Ge-based
EA modulator viable for future silicon photonics applications.
Photonic integrated single-sideband modulator/frequency shifter based on surface acoustic waves
Author(s):
Elaine C. S. Barretto;
Jørn M. Hvam
Show Abstract
Optical frequency shifters are essential components of many systems. In this paper, a compact integrated optical
frequency shifter is designed making use of the combination of surface acoustic waves and Mach-Zehnder
interferometers. It has a very simple operation setup and can be fabricated in standard semiconductor materials. The
performance of the device is analyzed in detail, and by using multi-branch interferometers, the sensitivity of the device to
fabrication tolerances can be drastically reduced.
A full-vectorial mode solver for bending waveguides by a modified finite difference method based on E-fields in cylindrical coordinate systems
Author(s):
Jinbiao Xiao;
Xiaohan Sun
Show Abstract
A full-vector mode solver for optical dielectric waveguide bends by using an improved finite difference method in terms
of transverse-electric field components is developed in a local cylindrical coordinate system. A six-point finite difference
scheme is constructed to approximate the cross-coupling terms for improving the convergent behavior, and the perfectly
matched layer absorbing boundary conditions via the complex coordinate stretching technique are used for effectively
demonstrating the leaky nature of the waveguide bends. The fundamental leaky modes for a typical bending rib
waveguide are computed, which shows the validity and utility of the established method.
Improvement of the channel crosstalk in narrow channel spacing arrayed waveguide gratings applying specially shaped couplers
Author(s):
Dana Seyringer
Show Abstract
Arrayed waveguide gratings (AWG) play a key role in dense wavelength division multiplexing (DWDM) systems. While
the standard channel count (up to 40) and standard channel spacing (100 GHz or 50 GHz) AWGs feature very good
transmission characteristics, increasing the channel counts and narrowing the channel spacings leads to a rapid increase
in the AWG size and this, in turn; causes the deterioration in optical performance like higher insertion loss and, in
particular, higher channel crosstalk. Channel crosstalk is a result of amplitude errors of the far field profile at the end of
the input coupler and phase errors appearing in the phased array as a result of possible effective index and geometrical
irregularities of the arrayed waveguides.
I our work we show that keeping the length of arrayed waveguides short and using specially-shaped couplers, both phase
and amplitude errors can be minimized and, as such, the channel crosstalk strongly improved. To demonstrate this effect,
we designed 256-channel, 25 GHz AWG with both, standard and also with specially-shaped couplers. The far field
distribution at the end of standard input coupler features strong amplitude errors causing the high channel crosstalk and
particularly very high background crosstalk. Applying the specially-shaped couplers led to elimination of amplitude
errors in the far field distribution and this had a positive effect on the transmission characteristics. The adjacent crosstalk
was improved by ~ 4 dB, non-adjacent crosstalk was improved by ~ 5 dB and background crosstalk by about 10 dB.