CubeSat single-photon detector module for investigating in-orbit laser annealing to heal radiation damage

TL;DR

This paper presents the design and ground testing of a CubeSat-compatible module capable of laser and thermal annealing of silicon SPADs, aiming to mitigate radiation damage effects for quantum satellite communications.

Contribution

It introduces a novel compact module for in-orbit laser annealing of SPADs, demonstrating ground-based feasibility in simulated space conditions.

Findings

Successful ground testing of the annealing module

Laser annealing reduces radiation-induced DCR in SPADs

Module design compatible with CubeSat form factor

Abstract

Single-photon avalanche photodiodes (SPADs) based on silicon are widely considered for quantum satellite communications but suffer from an increasing dark count rate (DCR) due to displacement damage in their active areas induced by proton radiation. When the DCR of SPADs exceeds a certain threshold, they become unusable for quantum communication protocols. Previous laboratory experiments have demonstrated that laser annealing of SPADs' active area with about 1~W optical power can significantly reduce radiation-induced DCR of synthetically irradiated SPADs. To assess the feasibility of in-orbit laser annealing on constantly irradiated SPADs in low-Earth orbit, we developed a module with a CubeSat form factor capable of both laser and thermal annealing of four silicon SPADs. Here we report the design and ground testing of this module, investigating laser annealing in a simulated space environment. Our results pave the way for an in-orbit trial that may prove this technology useful for future satellite missions with quantum receivers on board.