Tunable Optoelectronic Oscillator Using a Directly Modulated Microsquare Laser

A tunable optoelectronic oscillator (OEO) employing a directly modulated microsquare laser is proposed and experimentally demonstrated without using any external modulator and electrical bandpass filter. In our scheme, the OEO oscillates near the relaxation oscillation frequency at which the microsquare laser has the highest modulation efficiency. Microwave signals with the frequency tuned from 3.51 to 8.16 GHz are generated by tuning the bias current of the microsquare laser. Single sideband phase noise of -112.5 dBc/Hz. is obtained at a frequency offset of 10 kHz for the generated 7.48 GHz microwave signal.