Integrated fiber components based on chirally-coupled-core fibers for all-fiber amplifier

Abstract

The output power of fiber-based single-frequency amplifiers, e.g. for gravitational wave detectors, is typically limited by nonlinear effects (e.g. stimulated Brillouin scattering). In addition to a high output power, long-term stable and less complex laser systems are required. It has been shown that all-fiber amplifier systems can be a suitable option to avoid power scaling problems of single-frequency solid-state lasers with injection locking. Chirally-coupled-core (3C®) fibers have been specifically designed to enable single-mode operation with a large mode area core to overcome these limitations. 3C®-fibers consist of a step-index fiber structure, whose signal core is additionally chirally surrounded by one or more satellite cores. For this purpose, the all-solid design of 3C®-fibers allows a manufacturing process of fiber-based components. We present various optical components based on 3C®-fibers for the realization of a single-frequency all-fiber amplifier. These amplifiers typically consist of a mode field adapter (MFA), cladding light stripper (CLS) and pump combiner (PC) to minimize the excitation of higher order modes, remove residual pump light and optimize the coupling efficiency of the pump light in the 3C®-fibers. The components have been specifically designed for the first time with 3C®-fibers and tested according to their performance. As a first prototype, a robust and monolithic fiber amplifier with an ytterbiumdoped 3C®-fiber in combination with commercially available standard fibers was developed. Overall, the fiber amplifier achieves an optical output power of 165W in a linearly polarized TEM00-mode. This work emphasizes the high potential of amplifiers based on 3C®-fibers as laser sources for the next generation of gravitational wave detectors and demonstrates that compact and robust amplifiers can be realized using 3C®-fibers.