SBIR-STTR Award

Ultrasensitive detection of visible light has a wide range of applications, including laser ranging and free-space optical communications. Ultimate sensitivity is achieved when individual return photons are counted with high probabilities of detection, low probabilities of false counts, and high bandwidth. Previously, Vacuum photomultiplier tubes provided good single photon detection sensitivities but with limited bandwidth, while semiconductor solutions provide high bandwidth or high sensitivity, but not both. LightSpin proposes to develop a novel semiconductor solution to bridge the gap between bandwidth and ultimate sensitivity. The approach recognizes ultra-scaling of single photon avalanche diode (SPAD) arrays enables substantial improvements in bandwidth to be achieved. The approach uses GaInP, a wide band gap compound semiconductor with superior characteristics for high speed detection of visible light with low noise. The Phase I goal is to achieve single photon sensitivities at bandwidths approaching 1 GHz, laying the foundation for a Phase II effort to extend the bandwidth to 10 GHz.

Benefit:
The proposed ultra-scaling of SPAD arrays has the potential to achieve bandwidths approaching 10 GHZ and gain-bandwidth products approaching 100 THz, outperforming all competing, room temperature approaches. Target commercial applications include lidar (projected market value of $0.5B in 2018) and free space optical communications ($50M in 2018). LightSpins initial approach is targeted for highest performance for visible light, but is readily extended to the near infrared wavelengths commonly used for automobile lidar and autonomous robotic applications. Achieving an order of magnitude higher sensitivity will enable these lidar systems to achieve increased range and lower cost, providing a substantial advantage to the consumer.

Keywords:
single photon, single photon, free-space optical communications, APD, single photon avalanche diode, SPAD, LIDAR, SiPM, Avalanche photodiode

Ultrasensitive detection of visible light has a wide range of applications, including laser ranging and free space optical communications. Ultimate sensitivity is achieved when individual return photons are counted with high probabilities of detection, low probabilities of false detection, and precision timing. Previously, high bandwidth was only achieved with PIN photodiode and avalanche photodiodes, with detection limits of 1000 and 100 photons respectively, though bandwidth in excess of 10 GHz is feasible. LightSpin Technologies, Inc. proposed that scaling of single photon avalanche diode (SPAD) arrays to very tight pitches could be expected to achieve bandwidths in excess of 1 GHz, for the first time enabling simultaneous single photon detection and wide bandwidth operation in a solid-state detector. In Phase I, LightSpin demonstrated the capability to scale SPAD arrays to 11 micron pitch and demonstrated a bandwidth improvement in agreement with theory. In Phase II, we propose to continue the scaling effort to 5 micron pitch, enabling GHz and multi-GHz detection bandwidth with single photon sensitivity.

Benefit:
The proposed ultra-scaling of SPAD arrays has the potential to achieve bandwidth approaching 10 GHz and gain-bandwidth products approaching 100 THz, outperforming all room-temperature alternatives. Single photon counting modules and avalanche photodiodes markets are $246M/year and $167M/year respectively as a part of the total global photonic detectors market growing at a compounded annual growth rate (CAGR) of 15% through 2019. Avalanche photodiodes are a critical component of many high performance lidar systems, and achieving an order of magnitude improvement in detection sensitivity translates directly to increased range, reduced transmitted laser power, and lower cost. LightSpins approach is a platform technology that can be readily adapted to not only address visible light photodetection, but also near infrared and eye-safe wavelengths critical to many commercial lidar systems.

Keywords:
Geiger Mode, APD, single photon avalanche diode, Avalanche photodiode, SPAD, SPAD array, SiPM