A harmonic colliding-pulse mode-locked semiconductor laser for stable subterahertz pulse generation

A 192-GHz, sixth-harmonic colliding-pulse mode-locked InGaAsP-InP strained QW semiconductor laser that has a monolithic periodic saturable-absorber configuration is presented. The generation of nearly transform-limited, 0.75-ps pulses with a side-mode suppression ratio of about 27 dB at the central mode is demonstrated. The temporal repetition rate of the pulses was measured for the first time with the accuracy of the synthesizer by photonic downconversion using optical modulation sidebands. The rate for the pulses under a higher saturable-absorber voltage of -2.33 V had a 10-dB reduction RF-spectrum width of 1.1 MHz with a resolution of 300 kHz. The repetition rate versus reverse voltage was linear in a range from -750 to -900 mV.