50 research outputs found
Coherent beam combining with multilevel optical phase-locked loops
Coherent beam combining (CBC) technology holds the promise of enabling laser systems with very high power and near-ideal beam quality. We propose and demonstrate a novel servo system composed of multilevel optical phase lock loops. This servo system is based on entirely electronic components and consequently can be considerably more compact and less expensive compared to servo systems made of optical phase/frequency shifters. We have also characterized the noise of a 1064 nm Yb-doped fiber amplifier to determine its effect on the CBC and studied theoretically the efficiency of combining a large array of beams with the filled-aperture implementation. In a proof-of-concept experiment we have combined two 100 mW 1064 nm semiconductor lasers with an efficiency of 94%
A self-equalizing photo detector
A self-equalizing photo-detector (SEPD) that mitigates the bandwidth limitations of electro-optical components of optical communication systems is demonstrated, enabling higher rate of data transmission, using slower components. Unlike other all-optical equalization schemes, SEPD is optically wide band, thus does not require wavelength tuning
Nanophotonic projection system
Low-power integrated projection technology can play a key role in development of low-cost mobile devices with built-in high-resolution projectors. Low-cost 3D imaging and holography systems are also among applications of such a technology. In this paper, an integrated projection system based on a two-dimensional optical phased array with fast beam steering capability is reported. Forward biased p-i-n phase modulators with 200MHz bandwidth are used per each array element for rapid phase control. An optimization algorithm is implemented to compensate for the phase dependent attenuation of the p-i-n modulators. Using rapid vector scanning technique, images were formed and recorded within a single snapshot of the IR camera
Self-equalizing photodiodes, a hybrid electro-optical approach to tackle bandwidth limitation in high-speed signaling
In this paper we provide the design details of self-equalizing photodetectors which enable higher data rate transmission by improving the overall bandwidth of the bandwidth limited transmission link, through a hybrid electro-optical solution. Two different self-equalizing photodiodes, one having fixed equalization and the other being programmable are presented as proof of concept
Coherent power combination of two Master-oscillator-power-amplifier (MOPA) semiconductor lasers using optical phase lock loops
Using heterodyne Optical Phase-Locked Loops (OPLLs), two 1W high power 1550 nm master-oscillator-power-amplifier (MOPA) semiconductor lasers operating as current controlled oscillators are phase-locked to a 1 mW reference laser. The signals of the two MOPAs are then coherently combined and their mutual coherence is studied. In each OPLL, the acquisition range is increased to +/-1.1GHz with the help of an aided- acquisition circuit. Control of the phase of a single slave MOPA is demonstrated using a RF phase shifter. The differential phase error between two MOPAs locked to the common reference laser is typically 22 degrees
Electronic Two-Dimensional Beam Steering for Integrated Optical Phased Arrays
This paper presents electrical beam steering in an integrated 4x4 2D optical phased
array (OPA) on a silicon on insulator (SOI) process enabling fast and repeatable beam steering for
next generation projection, tracking, and imaging
Nanophotonic coherent imager
An integrated silicon nanophotonic coherent imager (NCI), with a 4 × 4 array of coherent pixels is reported. In the proposed NCI, on-chip optical processing determines the intensity and depth of each point on the imaged object based on the instantaneous phase and amplitude of the optical wave incident on each pixel. The NCI operates based on a modified time-domain frequency modulated continuous wave (FMCW) ranging scheme, where concurrent time-domain measurements of both period and the zero-crossing time of each electrical output of the nanophotonic chip allows the NCI to overcome the traditional resolution limits of frequency domain detection. The detection of both intensity and relative delay enables applications such as high-resolution 3D reflective and transmissive imaging as well as index contrast imaging. We demonstrate 3D imaging with 15μm depth resolution and 50μm lateral resolution (limited by the pixel spacing) at up to 0.5-meter range. The reported NCI is also capable of detecting a 1% equivalent refractive index contrast at 1mm thickness
Single-chip photonic deep neural network for instantaneous image classification
Deep neural networks with applications from computer vision and image
processing to medical diagnosis are commonly implemented using clock-based
processors, where computation speed is limited by the clock frequency and the
memory access time. Advances in photonic integrated circuits have enabled
research in photonic computation, where, despite excellent features such as
fast linear computation, no integrated photonic deep network has been
demonstrated to date due to the lack of scalable nonlinear functionality and
the loss of photonic devices, making scalability to a large number of layers
challenging. Here we report the first integrated end-to-end photonic deep
neural network (PDNN) that performs instantaneous image classification through
direct processing of optical waves. Images are formed on the input pixels and
optical waves are coupled into nanophotonic waveguides and processed as the
light propagates through layers of neurons on-chip. Each neuron generates an
optical output from input optical signals, where linear computation is
performed optically and the nonlinear activation function is realised
opto-electronically. The output of a laser coupled into the chip is uniformly
distributed among all neurons within the network providing the same per-neuron
supply light. Thus, all neurons have the same optical output range enabling
scalability to deep networks with large number of layers. The PDNN chip is used
for 2- and 4-class classification of handwritten letters achieving accuracies
of higher than 93.7% and 90.3%, respectively, with a computation time less than
one clock cycle of state-of-the-art digital computation platforms. Direct
clock-less processing of optical data eliminates photo-detection, A/D
conversion, and the requirement for a large memory module, enabling
significantly faster and more energy-efficient neural networks for the next
generations of deep learning systems
An Adjustable Self Equalizing Photo Detector
An optically-wideband adjustable self-equalizing photo-detector (ASEPD), capable of reviving eye closure due to limited bandwidth of electro-optical components in an optical link, is presented. The ASEPD enables use of various slower electro-optical components in faster data links
Ka-Band SiGe Receiver Front-End MMIC for Transponder Applications
A fully integrated, front-end Ka-band monolithic microwave integrated circuit (MMIC) was developed that houses an LNA (low noise amplifier) stage, a down-conversion stage, and output buffer amplifiers. The MMIC design employs a two-step quadrature down-conversion architecture, illustrated in the figure, which results in improved quality of the down-converted IF quadrature signals. This is due to the improved sensitivity of this architecture to amplitude and phase mismatches in the quadrature down-conversion process. Current sharing results in reduced power consumption, while 3D-coupled inductors reduce the chip area. Improved noise figure is expected over previous SiGe-based, frontend design