Three-port beam splitters-combiners for interferometer applications

TL;DR

This paper derives coupling relations for three-port beam splitters-combiners and explores their application in interferometers, demonstrating potential for improved signal separation and all-reflective cavity configurations.

Contribution

It introduces generic phase and amplitude coupling relations for three-port beam splitters-combiners and applies them to enhance interferometer performance.

Findings

Reflection grating can act as a coupler for Fabry-Perot ring cavities

Impedance-matched interferometers can serve as all-reflective ring mode cleaners

Almost complete separation of carrier power and phase signal is achievable in undercoupled regimes

Abstract

We derive generic phase and amplitude coupling relations for beam splitters-combiners that couple a single port with three output ports or input ports, respectively. We apply the coupling relations to a reflection grating that serves as a coupler to a single-ended Fabry-Perot ring cavity. In the impedance-matched case such an interferometer can act as an all-reflective ring mode cleaner. It is further shown that in the highly undercoupled case almost complete separation of carrier power and phase signal from a cavity strain can be achieved.