Angled fiber-coupled MgF2 microcavities for nonlinear optics in 1.5 and 2μm bands

Abstract

A versatile angled fiber coupling platform for magnesium fluoride whispering gallery mode resonators is used to investigate nonlinear frequency conversion across 1.5 and 2 $\mu m$ bands. We characterize MgF${}_2$ microcavities of varying sizes (4.3 mm, 1.9 mm, and 0.73 mm in diameter), achieving quality factors up to $2\times 10^9$ at $1.55\mu m$ and $5\times 10^8$ at $1.94\mu m$. In the telecom regime, we observe rich nonlinear phenomena including Kerr comb generation, Brillouin lasing, and Raman lasing. Extending to the 2 $\mu m$ band, we demonstrate four-wave mixing in a sub-millimeter cavity, highlighting the platform’s potential for the 2 $\mu m$ band mid-infrared nonlinear optics.