Ultrabroadband Passive Laser Noise Suppression to Quantum Noise Limit through on-chip Second Harmonic Generation

TL;DR

This paper presents an all-optical, passive noise suppression device using second-harmonic generation in nanophotonic lithium niobate waveguides, achieving broadband stabilization of laser intensity noise from DC to over 10 GHz.

Contribution

It introduces a scalable, wide-bandwidth, passive laser noise suppression method that operates without resonant locking, surpassing traditional electronic feedback and optical resonator techniques.

Findings

Suppresses relative intensity noise by 25 to 60 dB across the bandwidth

Stabilizes a fiber amplifier output to the shot-noise limit

Operates passively at a pump-depletion stationary point

Abstract

Laser intensity noise limits performance in quantum sensing, metrology, and computing. Existing stabilization methods face a trade-off between bandwidth and complexity: electronic feedback loops are speed-limited, while optical resonators are constrained by narrow linewidths and locking requirements. Here, we demonstrate an all-optical "noise eater" that passively suppresses intensity fluctuations from DC to >10 gigahertz. By leveraging high-efficiency second-harmonic generation in nanophotonic lithium niobate waveguides, we operate at a pump-depletion stationary point where input fluctuations are decoupled from the output to first order. This passive and nonresonant nanophotonic device suppresses relative intensity noise by 25 to 60 dB over the full measurement bandwidth and stabilizes a noisy fiber amplifier output to the shot-noise limit. Our results establish a scalable, wide-bandwidth paradigm for laser stabilization essential for high-throughput quantum technologies and deployable photonic sensing systems.