Photonic integrated passively mode-locked ring laser emitting picosecond short optical pulses in the L-band

An InP based passively mode-locked ring laser geometry emitting picosecond short pulses at 1570 nm is experimentally demonstrated and studied by static and dynamic emission characterization. The laser cavity incorporates two symmetrically placed absorbers and four gain sections. The cavity length corresponds to a repetition rate of 23.3 GHz. Due to the symmetric ring design, pulses are travelling in clockwise and counterclockwise direction hence allowed to overlap inside the absorber sections. By applying selected absorber reverse bias voltages and for different gain section injection currents, time-domain, spectral-domain and radio-frequency domain results are presented and discussed. Optical pulses as short as 1.4 ps and spectral widths exceeding 10 nm (-3dB) are generated. The lowest pulse-to-pulse timing jitter amounts to 31.7 fs (mode beat line width of 80 kHz), the time-bandwidth product for the shortest pulses amounts to 0.7.