In-fibre fabry-pérot microresonator with 140 million Q-factor

Summary form only given. Ring-type and whispering-gallery mode microresonators combine strong light confinement with high optical non-linearity to give rise to and enable efficient nonlinear optical parametric frequency conversion processes [1], stimulated Brillouin and Raman scattering. Here we demonstrate a novel Fabry-Pέrot (FP) microresonator consisting of a several mm long standard singlemode optical fibre (SMF), whose end facets are covered with a highly reflective dielectric coating. The resonator is embedded in a standard ceramic ferrule (Fig.1a) for alignment-free, mechanically robust connection and modematching with any optical fibre component (Fig.1b)(a related resonator geometry was demonstrated in [2]). The free spectral range is approximately 9.7 GHz and the microresonator has a single-mode characteristic (Fig.1c). The group velocity dispersion (GVD) is solely determined by the SMF, as the dispersion of the dielectric coating is flat by design. An important feature of the FP microresonators is freedom of design of its principal parameters. First, the FSR is defined by the length of the cavity and can be adjusted by using standard fibre connector polishing techniques. Secondly, the dielectric coating allows for dispersion engineering by applying a non-zero group delay dispersion. This opens up new possibilities for frequency comb generation in the visible and mid-IR, dispersion flattening and ultra-short soliton pulse formation. Lastly, the resonator design enables the use of numerous types of optical fibres including highly nonlinear, dispersion engineered, mid-infrared or active gain fibres.