Self-starting mode locking by multi-spatial-mode active waveguiding

We demonstrate a novel principle of self-starting mode locking in a compact semiconductor laser diode, where the needed saturable loss is provided by spatial effects resulting from multi-spatial-mode active waveguiding. The demonstrated device operates over a 1.54 microm wavelength range and has a repetition rate of 47 GHz. The pulse width is below 5 ps, and the average power coupled to the cleaved single-mode fiber is nearly 0 dBm.