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

Abstract

International audienceWe 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: μ- and mmspheres of SiO2 or monocrystalline disks. In this paper we present several approaches which have been investigatedin 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

Optical techniques for microwave frequency stabilization : Resonant versus delay line approaches and related modelling problems

“…Thus, the equivalent microwave Q factor of this system can be computed from equations (3) and (8) = Ω Equation (9) shows that the equivalent microwave Q factor of the optical resonator is the optical Q factor multiplied by the ratio of the microwave modulation frequency to the optical frequency. As an example, if we consider a 20 GHz application, using a λ = 1.5 μm laser, the frequency ratio is 10 4 , and thus the equivalent microwave Q is reduced by 10 4 compared to the optical Q factor.…”

“…These resonators are depicted in Figure 3. The coupling techniques and the measurement set-up for the test of the mini-disk or the silica sphere resonators have been described elsewhere [5,9]. It uses tapered fiber and a piezoelectric nanometer range control for the coupling of the resonators.…”