Ultra-low Brillouin scattering in anti-resonant hollow-core fibers

Abstract

Sensitive optical experiments in fiber, including for applications in communications and quantum information, are limited by the noise generated when light scatters from thermally excited guided-acoustic phonons. Novel fibers, such as microstructured fibers, offer control over both optical and acoustic waveguide properties, which can be designed to mitigate optomechanical noise. Here, we investigate the optomechanical properties of microstructured anti-resonant hollow-core fibers and demonstrate their promise as a low-noise fiber platform. By developing an ultra-sensitive spectroscopy technique, a seven capillary anti-resonant hollow-core fiber is found to exhibit record low optomechanical coupling (<10−4 W−1 m−1), in agreement with comprehensive numerical calculations. The largest scattering occurs from a guided acoustic mode in the air confined in the core of the fiber. Acoustic resonances in the silica, due to minimal overlap with the optical mode in the core, scatter a hundred times less, resulting in negligible depolarization noise. The largest optomechanical interactions in anti-resonant hollow-core fibers are found to be at least three (five if evacuated) orders of magnitude weaker than those in conventional single-mode fibers, which makes this class of fibers a promising platform for low noise applications, including quantum information processing and optical communication.