Photodiode quantum efficiency for 2-{\mu}m light in the signal band of gravitational wave detectors

TL;DR

This study evaluates the performance of extended-InGaAs photodiodes at 2 μm wavelength for gravitational wave detection, revealing a trade-off between dark noise reduction and detection efficiency at lower temperatures.

Contribution

It provides the first characterization of how temperature affects quantum efficiency and dark noise in extended-InGaAs photodiodes for 2 μm applications.

Findings

Dark noise decreases with temperature

Detection efficiency decreases with temperature

Current photodiodes are inadequate for 2 μm gravitational wave detection

Abstract

Quantum technologies with quantum correlated light require photodiodes with near-perfect `true' quantum efficiency, the definition of which adequately accounts for the photodiode dark noise. Future squeezed-light-enhanced gravitational wave detectors could in principle achieve higher sensitivities with a longer laser wavelength around 2 {\mu}m. Photodiodes made of extended InGaAs are available for this range, but the true quantum efficiency at room temperature and the low frequency band of gravitational waves is strongly reduced by dark noise. Here we characterize the change in performance of a commercial extended-InGaAs photodiode versus temperature. While the dark noise decreases as expected with decreasing temperature, the detection efficiency unfortunately also decreases monotonically. Our results indicate the need for a dedicated new design of photodiodes for gravitational wave detectors using 2-{\mu}m laser light.