High-Q optical resonators for laser stabilization in microwave photonics oscillators

New resonators are investigated in order to design compact and high performances microwave oscillators. Resonators become optical ones, with low dimensions due to short wavelengths. The optical resonator creates an optical frequency comb with microwave spacing. Each mode of this comb is characterized by an optical Q factor (Qopt) and an equivalent RF Q factor (Qrf). At 1.55 mum, this frequency ratio is about 104 at 20 GHz and Qopt must be at least equal to 108 to obtain a quality at 20 GHz better than the microwave resonators. We present different high-Q optical resonators and an application of one of them to microwave photonics oscillators. These optical resonators have really high Q factors. WGM resonators are potentially performing for highly compact devices and fibered resonators are efficient and easily integrated in a complete system. They are really interesting for laser stabilization in photonics microwave applications, as shown with the performances of this OEO, and we are actually improving the efficiency of such optical resonators and oscillators.