All-optical microwave oscillator based on semiconductor optical amplifier and stimulated Brillouin scattering

An all-optical microwave oscillator is proposed and experimentally demonstrated. Based on a pure photonic feedback loop, this system can generate a photonic microwave signal without optical–electrical–optical conversion or any electrical microwave devices. A semiconductor optical amplifier implements the functions of microwave envelope detection and feedback modulation. Meanwhile, Brillouin-selective sideband amplification is employed to lock oscillation frequency. In experiment, a good quality microwave signal with a frequency of 10.8 GHz is obtained. The tunability is also demonstrated by adjusting the Brillouin pump wavelength.