Wavelength tuning in self-seeded gain switched Fabry-Perot laser diode with moire grating

The authors propose a simple method for generating wavelength tunable singlemode picosecond pulses at a fixed repetition rate. This method is based on self-seeding a Fabry-Perot (FP) laser diode having a fibre external cavity formed by a moire grating with a proper channel spacing. Stepwise wavelength tuning over a large range can be achieved by changing the FP cavity roundtrip phase shift, and fast electrical tuning is possible by incorporating a phase-control section into the FP cavity. By using a two-channel moire grating and a temperature-controlled FP laser diode, tuning of picosecond pulses at a repetition rate of ~2 GHz between two wavelengths ~11 nm apart is demonstrated. A sidemode suppression ratio of >25 dB has been achieved