Abstract

Optical parametric oscillators (OPOs) emit narrow-linewidth light that is widely tunable in wavelength. In particular in the mid infrared, they are of prime interest because a single device can cover the entire wavelength range between 3 and 5 μm. Their realizations based on whispering gallery resonators (WGRs) provide a small footprint and ultra-low pump thresholds. We demonstrate millimeter-sized WGR based OPOs pumped with compact diode lasers operating at 1.55 μm wavelength. The parametric oscillation is tunable between 2.3 and 5.1 μm wavelength with milliwatt output powers. Tuning is achieved by changing the temperature of the resonator or by varying the pump wavelength. Operating the OPO at the point of degeneracy enables to generate THz-wide frequency combs centered around 3.1 μm wavelength. Our results show that whispering gallery resonators made of non-oxide materials can be the key component for realizing miniaturized wavelength-flexible sources for coherent mid infrared light.

© 2024 The Author(s)