A characterization bench to analyse various types of optical WGM resonators for high spectral purity microwave sources applications

We have set up a characterization bench to test the optical and microwave properties of high Q optical whispering gallery mode resonators. The bench comprises nanometer scale precision 3D displacement stages mounted on an anti-vibration table in order to get a very fine coupling between the optical resonator and the tapered fibers used for coupling. This bench can be adapted to different types of resonators: mum- and mm-spheres of SiO₂ or monocrystalline disks. In this paper we present several approaches which have been investigated in order to test these resonators. Different types of optical sources have been used: a broadband ´white light´ source around 1550 nm, a T-control free-running laser emitting at ~1550 nm, an external cavity laser with a narrow spectral width. We have also performed a temperature control of the sphere. Finally, we are trying to lock the laser on a sphere optical mode in order to get a stable system