Low noise resonant amplification by optical injection-locking and residual phase noise cancellation

TL;DR

This paper presents a novel optical amplifier that combines injection locking with feed-forward phase noise cancellation to achieve low noise, high gain, and spectral purity preservation, suitable for low-power optical references.

Contribution

The authors introduce a wavelength-agnostic, residual phase noise cancellation technique that enhances injection-locked lasers for low-noise optical amplification.

Findings

Achieves up to 38 dB phase-noise reduction at >1 kHz Fourier frequencies.

Enables ASE-free amplification of low-power, low-noise optical references.

Maintains spectral purity while providing high gain and low noise.

Abstract

We demonstrate a low noise, high-gain, resonant optical amplifier that combines injection locking with feed-forward cancellation of residual phase noise. The wavelength-agnostic architecture uses a commercial semiconductor diode laser as a power amplifier while preserving the spectral purity of a weak reference. Although injection locking enforces phase coherence, finite residual phase noise within the locking regime limits high-fidelity transfer of low phase noise from the reference laser to the injection-locked laser, particularly at large gain. Here, the residual phase error is measured via optical heterodyne detection and canceled using feed-forward phase correction. Compared to injection locking alone, the amplifier achieves up to 38 dB phase-noise reduction at Fourier frequencies above 1 kHz for injection ratios down to -57 dB. This approach enables ASE-free amplification of low-power, low-noise optical references, including individual lines from optical frequency combs.