A Simple and Robust Balanced Homodyne Detector for High-Repetition-Rate Pulsed Sources

TL;DR

This paper presents a new balanced homodyne detector design optimized for high-repetition-rate pulsed sources, offering improved linearity, noise performance, and simplicity over conventional architectures.

Contribution

The authors introduce a direct amplification approach for high-speed pulsed homodyne detection, supported by a theoretical model and experimental validation.

Findings

Achieved a maximum SNR of about 14 dB.

Demonstrated shot-noise-limited scaling of signal variance.

Confirmed negligible inter-pulse correlations.

Abstract

We design and experimentally characterize a balanced homodyne detector optimized for high-repetition-rate (100 MHz) pulsed optical sources. Unlike conventional transimpedance-amplifier architectures, which suffer from nonlinearities and dynamic instabilities with ultrashort pulses, our approach allows to directly amplify the photocurrent extracted at the common photodiode node without feedback loops. A theoretical model describing the detector response, noise, and pulse-to-pulse correlations is developed, providing quantitative predictions for the signal variance, signal-to-noise ratio (SNR), and inter-pulse correlations. Implemented with two matched InGaAs photodiodes illuminated by a 1030 nm mode-locked laser at 100 MHz, the detector exhibits excellent linearity and shot-noise-limited scaling of the signal variance with optical power. Optimizing the temporal integration window yields a maximum SNR of about 14 dB, while correlation measurements confirm negligible inter-pulse correlations. These results demonstrate that the proposed architecture offers a robust and simple solution for high-speed pulsed homodyne detection, suitable for quantum optics and continuous-variable quantum information applications.