Optical signal generation at millimeter-wave repetition rates using semiconductor lasers with pulsed subharmonic optical injection

A new technique is presented and investigated systematically which generate s optical signals at millimeter-wave repetition rates from a semiconductor laser, without the need for an intracavity saturable absorber. Optical puls es are generated from a long-cavity semiconductor laser with a repetition r ate equal to its cavity resonant frequency by injecting short optical pulse s at one of the cavity resonance subharmonics. A rate-equation model is pro posed to explain the mechanism of this subharmonic optical injection method . Optical pulses with repetition rates of 35 and 56 GHz are generated using the proposed scheme from a semiconductor laser with a distributed Bragg re flector and a Fabry-Perot laser diode, respectively. The performance of the generated pulses is also evaluated in terms of detected RF power at the re petition frequencies, the subharmonic suppression ratio, phase noise, and t iming jitter as a function of frequency detuning, injected optical power, l aser bias current, and, finally, the subharmonic number. It is found that t he generated optical pulses exhibit large subharmonic suppression ratio (>1 7 dB), large locking ranges >400 MHz, low levels of phase noise (similar to -93 dBc/Hz@10 kHz) and timing jitter (<0.41 ps over 100 Hz to 10 MHz), and large tolerance to variations in operating parameters.