5,446 research outputs found
InGaAsSb/GaSb lasers and photodetectors integrated on a silicon-on-insulator waveguide circuit for spectroscopic applications
International audienc
A Large-scale Distributed Video Parsing and Evaluation Platform
Visual surveillance systems have become one of the largest data sources of
Big Visual Data in real world. However, existing systems for video analysis
still lack the ability to handle the problems of scalability, expansibility and
error-prone, though great advances have been achieved in a number of visual
recognition tasks and surveillance applications, e.g., pedestrian/vehicle
detection, people/vehicle counting. Moreover, few algorithms explore the
specific values/characteristics in large-scale surveillance videos. To address
these problems in large-scale video analysis, we develop a scalable video
parsing and evaluation platform through combining some advanced techniques for
Big Data processing, including Spark Streaming, Kafka and Hadoop Distributed
Filesystem (HDFS). Also, a Web User Interface is designed in the system, to
collect users' degrees of satisfaction on the recognition tasks so as to
evaluate the performance of the whole system. Furthermore, the highly
extensible platform running on the long-term surveillance videos makes it
possible to develop more intelligent incremental algorithms to enhance the
performance of various visual recognition tasks.Comment: Accepted by Chinese Conference on Intelligent Visual Surveillance
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GaSb-based integrated lasers and photodetectors on a silicon-on-insulator waveguide circuit for sensing applications in the shortwave infrared
We report our results on GaSb photodiodes and lasers integrated on a Silicon-On-Insulator waveguide circuit. The photodiodes operate at room temperature with 0.4A/W responsivity for grating-assisted coupling and >1 A/W for an evanescent design. On the other hand, integrated Fabry-Perot lasers operate in continuous wave at room temperature with a threshold current of 49.7mA
Silicon-on-insulator shortwave infrared wavelength meter with integrated photodiodes for on-chip laser monitoring
This paper demonstrates a very compact wavelength meter for on-chip laser monitoring in the shortwave infrared wavelength range based on an optimized arrayed waveguide grating (AWG) filter with an integrated photodiode array. The AWG response is designed to obtain large nearest neighbor crosstalk (i. e. large overlap) between output channels, which allows accurately measuring the wavelength of a laser under test using the centroid detection technique. The passive AWG is fabricated on a 220 nm silicon-on-insulator (SOI) platform and is combined with GaInAsSb-based photodiodes. The photodiodes are heterogeneously integrated on the output grating couplers of the AWG using DVS-BCB adhesive bonding. The complete device with AWG and detectors has a footprint of only 2 mm(2) while the measured accuracy and resolution of the detected wavelength is better than 20pm. (C)2014 Optical Society of Americ
Quantification of optical pulsed-plane-wave-shaping by chiral sculptured thin films
The durations and average speeds of ultrashort optical pulses transmitted
through chiral sculptured thin films (STFs) were calculated using a
finite-difference time-domain algorithm. Chiral STFs are a class of
nanoengineered materials whose microstructure comprises parallel helicoidal
nanowires grown normal to a substrate. The nanowires are 10-300 nm in
diameter and m in length. Durations of transmitted pulses tend to
increase with decreasing (free-space) wavelength of the carrier plane wave,
while average speeds tend to increase with increasing wavelength. An increase
in nonlinearity, as manifested by an intensity-dependent refractive index in
the frequency domain, tends to increase durations of transmitted pulses and
decrease average speeds. The circular Bragg phenomenon exhibited by a chiral
STFs manifests itself in the frequency domain as high reflectivity for normally
incident carrier plane waves whose circular polarization state is matched to
the structural handedness of the film and whose wavelength falls in a range
known as the Bragg regime; films of the opposite structural handedness reflect
such plane waves little. This effect tends to distort the shapes of transmitted
pulses with respect to the incident pulses, and such shaping can cause sharp
changes in some measures of average speed with respect to carrier wavelength. A
local maximum in the variation of one measure of the pulse duration with
respect to wavelength is noted and attributed to the circular Bragg phenomenon.
Several of these effects are explained via frequency-domain arguments. The
presented results serve as a foundation for future theoretical and experimental
studies of optical pulse propagation through causal, nonlinear, nonhomogeneous,
and anisotropic materials.Comment: To appear in Journal of Modern Optic
Integrated thin-film GaSb-based Fabry-Perot lasers: towards a fully integrated spectrometer on a SOI waveguide circuit
Several molecules of interest have their absorption signature in the mid-infrared. Spectroscopy is commonly used for the detection of these molecules, especially in the short-wave infrared (SWIR) region due to the low water absorption. Conventional spectroscopic systems consist of a broadband source, detector and dispersive components, making them bulky and difficult to handle. Such systems cannot be used in applications where small footprint and low power consumption is critical, such as portable gas sensors and implantable blood glucose monitors. Silicon-On-Insulator (SOI) offers a compact, low-cost photonic integrated circuit platform realized using CMOS fabrication technology. On the other hand, the GaSb material system allows the realization of high performance SWIR lasers and detectors. Integration of GaSb active components on SOI could therefore result in a compact and low power consumption integrated spectroscopic system. In this paper, we report the study on thin-film GaSb Fabry-Perot lasers integrated on a carrier substrate. The integration is achieved by using an adhesive polymer (DVS-BCB) as the bonding agent. The lasers operate at room temperature at 2.02 mu m. We obtain a minimum threshold current of 48.9mA in the continuous wave regime and 27.7mA in pulsed regime. This yields a threshold current density of 680A/cm(2) and 385A/cm(2), respectively. The thermal behaviour of the device is also studied. The lasers operate up to 35 degrees C, due to a 323 K/W thermal resistanc
Heterogeneous GaSb/SOI mid-infrared photonic integrated circuits for spectroscopic applications
Mid-infrared spectroscopy has gained significant importance in recent years as a detection technique for substances that absorb in this spectral region. Traditionally, a spectroscopic system consists of bulky equipment which is difficult to handle and incurs high cost. An integrated spectroscopic system would eliminate these disadvantages. GaSb-based active opto-electronic devices allow realizing mid-infrared light sources and detectors in the 2-3 mu m wavelength range for such integrated systems. Silicon photonics, based on Silicon-on-Insulator (SOI) waveguide circuits, on the other hand, is a well established technology based on high refractive index contrast waveguides, enabling ultra-compact passive integrated photonic circuits. Moreover, SOI waveguide circuit processing is compatible with CMOS processes. Hence, the integration of GaSb-based active devices onto SOI passive waveguide circuits potentially allows highly compact spectroscopic systems with a large degree of freedom in passive device design to improve the system performance. This approach has a high potential for several applications, e. g. an implantable glucose level monitor and gas sensing devices.
In this paper, we report our work on the integration of GaSb-based epitaxy onto SOI waveguide circuits. The heterogeneous integration is based on an epitaxial layer transfer process using the polymer divinylsiloxane-benzocyclobutene (DVS-BCB) as a bonding agent. The process is performed by transferring the epitaxial layer to an SOI waveguide circuit wafer through a die-to-wafer bonding process. With this approach, a bonding layer of 150 nm thickness is easily achievable. We also report our results on the integration of waveguide-based GaSb p-i-n photodetectors coupled to SOI waveguide circuits using evanescent coupling, which show a responsivity higher than 0.4A/W. The design of active and passive structures and the overall fabrication process will also be discussed
Heterogeneous integration of GaSb-based epitaxy on silicon-on-insulator: towards mid-infrared photonic integrated circuits for environmental and bio-medical applications
International audienc
Silicon-on-insulator spectrometers with integrated GaInAsSb photodiode array for wideband operation from 1500 to 2300 nm
Four echelle-type spectrometers with heterogeneously integrated GaInAsSb photodetectors on a silicon-on-insulator chip is realized. The operating wavelengths stretch from 1500 to 2300 nm. A maximum channel crosstalk of -10 dB, dark current of -2.5 mu A and responsivity of 0.61 A/W at 1530 nm and 0.7 A/W at 2200 nm were obtained
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