The hybrid integration of superconducting nanowire single photon detectors (SNSPDs) on various substrates and on-chip photonic structures provides a promising way to develop complicated photonic functions based on single photon detections on photonic chips. The photon-counting spectrometer for single-photon-level ultra-faint light is another interesting application. Recently, several works on photon-counting spectrometers based on SNSPDs and on-chip micro/nano-photonic structures have also been reported. In these works, the micro/nano-photonic structures modulate the spectral responses of SNSPDs. However, they also lead to scatter losses and limit the photon utilization of the measurement of single-photon-level ultra-faint light. It is an interesting topic that how to realize the SNSPD spectral response modulations without any photon loss. Cooperating with the team from Shanghai Institute of Microsystem and Information Technology (SIMIT, CAS, China), we proposed a novel reconstructive photon-counting spectrometer based on the cascaded absorption effect of a SNSPD array. In this scheme, the photons with different wavelengths are diffracted by a Rowland grating to different locations in the focusing region on the chip. The SNSPD array is across the focusing region. Each SNSPD in the array has different pattern, which control the absorption of the superconducting nanowire at different location. The spectral response of this SNSPD is determined by its pattern and the cascaded absorption effect of the SNSPDs before it. Base on this mechanism, the spectral response of every SNSPD in the array could be designed flexibly, supporting the function of reconstructive photon-counting spectrometer. In the measurement, the all photons would be absorbed in the SNSPD array without any photon loss in principle.

This work has published on Advanced Devices & Instrumentation (Adv. Devices Instrum. 2023;4: Article 0021. https://doi.org/10.34133/adi.0021) at 6^th Sep. 2023. The co-first author of this paper are Ph.D. candidate Jingyuan Zheng and Ph.D. candidate You Xiao from SIMIT. The corresponding author of this paper is Prof. Wei Zhang. Advanced Devices & Instrumentation is a Science Partner Journal in affiliation with Beijing Institute of Aerospace Control Devices (BIACD) and distributed by the American Association for the Advancement of Science (AAAS). Its mission is to promote high impact breakthroughs and application advances at all levels of electronics and photonics including device, system, and instrumentation with a goal of integration for functionalities.