Efficient laser noise reduction by locking to an actively stabilized fiber interferometer with 10 km arm imbalance

TL;DR

This paper introduces a laser noise reduction technique using an actively stabilized 10 km fiber Mach-Zehnder interferometer, achieving over 90 dB noise suppression and significantly improving frequency stability for long-distance fiber links.

Contribution

It demonstrates a highly effective laser noise reduction method with large arm imbalance, utilizing active stabilization and heterodyne detection in a fiber interferometer.

Findings

Out-of-loop frequency noise reduced by over 90 dB at 1 Hz

Fractional frequency stability of 1.12×10⁻¹⁶ at 1 s over 10 km fiber link

Improved stability by more than an order of magnitude compared to unstabilized setup

Abstract

We report a laser noise reduction method by locking it to an actively stabilized fiber-based Mach Zehnder interferometer with 10 km optical fiber to achieve large arm imbalance. An acousto optic modulator is used for interferometer stabilization and heterodyne detection. The out-of-loop frequency noise is reduced by more than 90 dB for Fourier frequency at 1 Hz. This structure presents an efficient laser noise reduction method both at high Fourier frequency and low Fourier frequency. The signal of stabilized laser is transferred via a 10 km fiber link with a fractional frequency stability of 1.12 times 10-16 at 1 s. Compared with the fractional frequency stability of that when the interferometer is not stabilized, more than one order of magnitude is improved.