Wideband Multi-Element Optical Receiver

As a response to the Navy SBIR Topic N212-126, GHz Optical Underwater Detection Receiver, Alphacore will develop a wide bandwidth, multi-element optical receiver to enable the extraction of both reflectivity and range features of objects in water. This proposed work will integrate advanced compact photo detectors with Alphacore’s innovative high-speed readout technology. The proposed system will be optimized for optical sensitivity in the blue-green wavelengths (400nm to 560nm) with sufficient dynamic range to detect signals in high clutter environments. In Phase II, Alphacore will design, fabricate and test prototype 750 x 1 and 750 x 2 pixels monolithic underwater lidar receivers. The main parameters of the design are >2GHz bandwidth, 10GSPS sampling rate, >1,000 samples buffer length in every pixel, >60dB SNR and linearity and programmable sampling rate and bandwidth. Alphacore’s solution is a monolithic CMOS IC that contains the sensitive linear mode avalanche photodiodes (APD) and all other needed functionality, including waveform samplers, digitizers, serializers and I/Os. The sampler architecture is based on a high-bandwidth transimpedance amplifier followed by highly linear track and hold stages. The 1,000-samplers-per-pixel architecture enables up to 100ns of sampled signal on the 10GS/s mode and 200ns on 5GS/s mode. Bandwidth is 2GHz and it can be traded off with power dissipation using a programmable setting. The sampling rate and buffer length are programmable as well. The first design version to undergo a tapeout will be a 750 x 1 and 750 x 2 -pixels arrays, the number of elements limited by the edge length (27mm) of the reticle in the selected CMOS process. However, several chips can be “mechanically” cascaded to provide more pixels, 4,500 x 1, as an example. 4,500 x 2 array is possible as well with the selected high-bandwidth, high-sampler-count architecture. This arrangement could be used for dual band receiver, as an example. Alphacore proposes the following approach to complete a prototype wideband, multi-element optical receiver by the end of Phase II. Optimize and send to fabrication high bandwidth lidar receiver design. The already designed and simulated ASIC will be taped out and tested. Evaluate the High Bandwidth Lidar Receiver IC design functionality. Alphacore will evaluate multi-element avalanche photodiodes (APDs) in linear mode with wide input bandwidths and low input noise. Alphacore will design, fabricate and characterize test boards, and our test laboratory has all the needed test equipment and the basic IC functionality testing  will take place there. Option Period: Integrate the Lidar Receiver IC with optics and a FPGA based camera system and test in simulated Marine environment. The tested Lidar Receiver IC from the base period will be integrated with commercially available optical elements identified in the Phase II Base period.