Fabrication and characterization of low loss MOMS resonators for cavity opto-mechanics

The study of the optomechanical coupling between the radiation pressure of a laser beam and a mechanical oscillator is an emerging field in quantum optics that is taking advantage of all the recent developments in micro-fabrication. The manipulation of the quantum state of light is within the reach of systems based on a Fabry-Perot cavity with a Micro-Opto-Mechanical-System (MOMS) resonators used as end-mirror. To approach the quantum regime, these micro devices must satisfy two basic requirements: low optical and mechanical losses. We have recently proposed a class of very low loss MOMS devices working in the 100 kHz frequency region, based on two-side MEMS processing bulk-micromachining. In this work we describe our latest process development, based on the used of pure aluminum as a masking layer for the optical coating during fabrication, that significantly improves the quality of the devices and the yield of the process, opening the way for their use in integrated systems for quantum optics. The devices show very high optical quality (finesse up to 10⁵ can be achieved in optical cavity) and a mechanical quality factor over 10⁶ at cryogenic temperatures.