Optical pulse generation with programmable positions in an actively mode-locked optical cavity

A novel, to our knowledge, approach for generating optical pulses with programmable positions in an actively mode-locked (AML) optical cavity is proposed and experimentally demonstrated. In the AML, active mode locking occurs when the cavity gain exceeds one, and the cavity round trip time equals integer multiples of the repetition period of the electrical driving signal. The generated optical pulses are present at the positions where the optical cavity operates at its maximum transmission points. By periodically controlling the cavity gain with the driving signal, the maximum transmission points can be manipulated using a periodic arbitrary waveform, allowing the positions of the generated optical pulses within one round trip time to be programmed. Thanks to the superposition of the circulating optical field within the optical cavity, the pulse width of the generated pulses can be greatly compressed. In a proof-of-concept experiment, optical pulses with programmable pulse numbers, pulse intervals, and pulse position distributions in one period are generated by programming the driving signals. Optical pulse compression is also successfully verified. Optical pulses with an approximate 34-ps pulse width, ultra-low pulse interval (about 200 ps), and linear positional distribution are achieved.