Scattered light reduction in Sagnac Speed Meters with Tunable Coherence

TL;DR

This paper introduces Tunable Coherence, a technique to suppress scattered light in Sagnac Speed Meters, achieving over 24 dB reduction and potentially improving sensitivity in high-precision optical instruments.

Contribution

The paper experimentally demonstrates Tunable Coherence to reduce scattered light in Sagnac interferometers and discusses its potential as a fundamental solution for ring resonators.

Findings

Achieved 24.2 dB scattered light suppression in a Sagnac interferometer.

Demonstrated controlled breaking of laser coherence length to suppress scattering.

Discussed the fundamental role of Tunable Coherence in ring resonator sensitivity enhancement.

Abstract

Sagnac Speed Meter and ring resonators can be used as high precision instruments, but they are limited in their sensitivity through scattered light causing non-linear noise. Here, we experimentally demonstrate a technique called Tunable Coherence, where the long coherence length of the laser is broken in a controlled way, to suppress the coupling of scattered light in a Sagnac interferometer. We demonstrate a scattered light suppression of 24.2 dB in a Sagnac interferometer and discuss the experimental limitations. Further, we show an analytical discussion on how Tunable Coherence could be a fundamental solution to light scattering back from optical surfaces into the counter propagating beam, which is an issue particularly in ring resonators.