Breakdown flash at telecom wavelengths in InGaAs avalanche photodiodes

TL;DR

This paper characterizes the fluorescence emitted during avalanche breakdown in InGaAs photodiodes used for telecom quantum key distribution, revealing a spectral distribution and demonstrating effective suppression through filtering.

Contribution

It provides the first detailed spectral analysis of breakdown fluorescence in InGaAs APDs and shows how spectral filtering can mitigate potential security vulnerabilities.

Findings

Breakdown fluorescence spans 1000-1600nm in InGaAs APDs.

Spectral filtering effectively suppresses fluorescence side channels.

Characterization of commercial InGaAs modules enhances understanding of security risks.

Abstract

Quantum key distribution (QKD) at telecom wavelengths (1260-1625nm) has the potential for fast deployment due to existing optical fibre infrastructure and mature telecom technologies. At these wavelengths, indium gallium arsenide (InGaAs) avalanche photodiode (APD) based detectors are the preferred choice for photon detection. Similar to their silicon counterparts used at shorter wavelengths, they exhibit fluorescence from recombination of electron-hole pairs generated in the avalanche breakdown process. This fluorescence may open side channels for attacks on QKD systems. Here, we characterize the breakdown fluorescence from two commercial InGaAs single photon counting modules, and find a spectral distribution between 1000nm and 1600nm. We also show that by spectral filtering, this side channel can be efficiently suppressed.