A vacuum integrated fibre Fabry-Pérot cavity setup for optical and optomechanical characterisation

Abstract

Fibre Fabry–Pérot cavities are miniaturised Fabry–Pérot cavities integrated on optical fibres. Their small size, open mode volume and intrinsic integration with optical fibres make them well suited for optomechanical experiments in which one studies the interaction between light and mechanical motion. The short cavity length enables enhancement of the vacuum optomechanical coupling strength and the open mode volume allows for the easy insertion of mechanical resonators or other quantum systems directly into the cavity. These features make fibre Fabry–Pérot cavities suited for many applications such as levitation of nano particles and quantum-enhanced inertial and force sensing. In this master’s thesis, an experimental platform was developed with the goal to enable optical and optomechanical characterisation of fibre Fabry–Pérot cavities consisting of a fibre mirror and a reflective mechanical resonator on a chip. To this end, an existing experimental setup for optical characterisation was improved upon through automatisation and a vacuum-integrated setup for optomechanical experiments was built and tested. The resulting experimental platform enables measurements of the resonance linewidth and free spectral range of fibre Fabry–Pérot cavities. Within the vacuum-integrated setup the cavity length can be locked to the drive laser. This setup will in future work be used for optomechanical experiments measuring the optomechanical coupling strength and controlling mechanical resonator modes utilising the optical spring effect and optomechanical damping.