Generation of short wavelength-tunable semiconductor laser pulses

Abstract

Self-seeding of a gain-switched Fabry-Perot laser diode with subsequent chirp compensation presents a simple way to generate pulses of a few picoseconds width tunable over more than 50 nm. Using this technique, neither highly sophisticated laser structures like Tunable Twin Guide (TTG) or multi-section DBR lasers, nor anti-reflection coatings of the facets as required for mode-locking, are needed. Using a dispersive cavity (e.g. 1 km of dispersive fiber) electrical wavelength tunability is possible. Detailed investigations of the switching behavior have shown that the switching occurs within less than 10 round-trips (typical 10.,1000 ns), and switching rates between two different emission wavelengths of more than 1 MHz have been demonstrated. The timing jitter of the single mode laser pulses is less than 500 fs. This is one order of magnitude smaller than the jitter of laser pulses generated by a gain-switched DFB-laser, allowing self-seeding to be used e.g. in high temporal resolution electro-optic sampling systems. Further compression of these laser pulses exploiting nonlinear effects in optical fibers (soliton compression) allows the generation of laser pulses with a width (FWHM) of less than 300 fs.