Upper Limit to the Transverse to Longitudinal Motion Coupling of a Waveguide Mirror

TL;DR

This paper measures the maximum possible coupling between transverse and longitudinal motions in a waveguide mirror, demonstrating a significant reduction compared to previous designs, which is crucial for minimizing phase noise in precision optical systems.

Contribution

The paper provides the first experimental upper limit on transverse to longitudinal coupling in a waveguide mirror, showing a substantial improvement over prior grating mirror measurements.

Findings

Upper limit of 1/17000 coupling with 95% confidence

Demonstrates reduced phase noise potential in waveguide mirrors

Improves understanding of nano-structured mirror stability

Abstract

Waveguide mirrors possess nano-structured surfaces which can potentially provide a significant reduction in thermal noise over conventional dielectric mirrors. To avoid introducing additional phase noise from motion of the mirror transverse to the reflected light, however, they must possess a mechanism to suppress the phase effects associated with the incident light translating across the nano-structured surface. It has been shown that with carefully chosen parameters this additional phase noise can be suppressed. We present an experimental measurement of the coupling of transverse to longitudinal displacements in such a waveguide mirror designed for 1064 nm light. We place an upper limit on the level of measured transverse to longitudinal coupling of one part in seventeen thousand with 95% confidence, representing a significant improvement over a previously measured grating mirror.