I was a member of the team that first modelocked a semiconductor laser. We did it first with GaAlAs and then with GaInAsP. These experiments generated pulses more than an order of magnitude shorter than anything previously achieved. One doesn’t get to do that too often over the course of a technical career. The first paper is Picosecond pulse generation with a cw GaAlAs laser diode. The second is c.w. modelocking of a GaInAsP diode laser.
First ABSTRACT: We report the generation of 20-ps optical pulses at microwave repetition rate from a GaAlAs double-heterostructure diode operating cw at room temperature. The diode is operated in an external optical resonator and is actively modulated at 3 GHz. The pulses are measured by autocorrelation using SHG in LiIO3. They are the shortest pulses ever reported for a cw laser diode.
Second ABSTRACT: Active cw modelocking of a GaInAsP double-heterostructure laser diode operating in an external cavity is reported. 18 ps pulses (f.w.h.m.) are obtained at a repetition rate of 2.1 GHz and a lasing wavelength of 1210 nm. The pulses were measured by autocorrelation using SHG in LiIO3. They are the shortest pulses ever recorded for a cw laser diode.
So read about the first modelocking of a semiconductor laser.