Photonic Integrated Circuit Assisted Single Photon Detectors (PICA SPDs)

Within this program, Physical Sciences Inc. (PSI) and the University of Illinois Urbana-Champaign (UIUC) will develop Photonic Integrated Circuit Assisted-Single Photon Detectors (PICA-SPDs) to increase the bandwidth and timing resolution of single-photon detectors (SPDs). Realizing low size, weight, and power (SWaP) SPDs with high saturation-rates and high timing-resolutions are critical for deploying of quantum technology in space. While the best superconducting nanowire SPDs (SNSPDs) can achieve saturation rates up to 100 MHz with timing resolutions of several 10rsquo;s of ps, these also require cryogenic environments, making their deployment in space a challenge. On the other hand, single photon avalanche photodiodes (SPADs) are low SWaP and can operate at room temperature with good efficiencies (gt;75%); however, the timing resolution is often 50 ps (or more) and the saturation rate is typically limited to 10s of MHz.To overcome the challenge of increasing both the timing resolution and saturation rate of SPAD arrays, our unique active-approach leverages high-speed, low-loss PIC modulators. Here, single-photon optical signals enter the PIC and are routed to a series of Mach-Zehnder Interferometer (MZI) switches. These fast, traveling-wave switches are driven by periodic signals having progressively higher frequencies to create a switch yard. As the photon stream enters each of the MZI switches, the different time-positions are routed to different outputs of each MZI, which isolates individual time-positions to enable readout using an array of SPDs. This approach enables an array of SPADs to operate together to achieve timing resolutions even surpassing SNSPDs with greatly enhanced saturation count rates to enable space-based quantum networking applications.