High-transmission fiber ring resonator for spectral filtering of master oscillator power amplifiers

Abstract

We experimentally characterize a fiber-based ring resonator constructed from two commercially available 2x2 polarization-maintaining directional couplers. This ring resonator has a maximum noise suppression of 25 dB and resonant transmission of 80% at 1550 nm. Its high transmission means this ring resonator is ideally suited for the spectral filtering of master oscillator power amplifier light sources in a robust, compact, and all-fiber package. The limits of such a ring resonator for use in gravitational-wave detectors are discussed, and we show how it could be used to filter the low-power amplifier section and reduce the noise suppression requirements for the final free-space mode-cleaner.