Mini and micro-resonators for the generation of high spectral purity microwave signals
Résumé
Optoelectronic Oscillators (OEOs) are an attractive alternative to electrical solutions for the generation of high spectral purity signal at high frequency. Indeed, carrying the microwave signal on an optical carrier offers the opportunity of long staorage time, with almost no dependence on signal frequency. For example, classical OEOs are based on kilometre long fiber delays and, in a relative simple setup, their performances exceed the ones of most microwave oscillators. However, the most promising OEOs architectures, in term of performances and integration level, are based on high Q optical resonators. After an introduction on the principle of OEOs and their various potential applications in advanced microwave systems, we will present recent results that we have obtained in this field.. First, the realization and characterization of silica, CaF2, MgF2 and LiNbO3 Whispering Gallery Modes (WGM) resonators with Q factors in the 10^8-10^9 range will be presented, together with related light coupling techniques for their practical use in OEOs demonstrations. Then the realization and characterization of fiber-ring resonators, that present Q factors exceeding 10^9 in a relatively simple architecture will be highlighted. Finally, dual-frequency laser sources that have been specifically realized for OEOs will be described.