LAUSR

The optoelectronic oscillators (OEOs) based on a 1.55-μm direct-modulated AlGaInAs/InP square microcavity laser without optical injection are demonstrated for narrow-linewidth photonic microwave signal generation. The square microcavity laser with a side length of 16 μm under an injection current of 14 mA is used in the experiment. High-quality photonic microwave signals with 3-dB linewidths around 30 Hz are obtained by the first harmonics of the single-loop and dual-loop OEOs. Single-sideband phase noise at 10 kHz frequency offset is as low as −116 dBc/Hz for the microwave signal. With the dual-loop OEO, the side-mode suppression ratios up to 55 dB are obtained for the first harmonics, and tunable microwave signals from 1.85 to 10.24 GHz are realized with narrow linewidths and low-phase noises.