On-chip integrated resonators for long-wave infrared photonics

On-chip optical resonators are extensively applied to many fields such as light sources through lasing or enhancement of material nonlinear effects, chemical and biological sensing, and optical network monitoring. Silicon-based on-chip resonators have been reported previously in near infrared (NIR) and shortwave infrared (SWIR), however integrated resonant structures remain still challenging for long-wave infrared (LWIR). In this work, we experimentally demonstrate the first on-chip integrated resonators in LWIR up to 8.4 µm. Two types of resonators, Fabry-Perot cavities and racetrack ring resonators, have been both investigated. Maximum quality factors Q = 2200 and Q = 3200 have been respectively observed for Fabry-Perot cavity and racetrack ring resonator at a wavelength around 8 µm. These resonant structures lay the foundation for new generation of integrated photonics circuits that open the path towards miniaturized multi-functional LWIR systems.