A system for producing a laser light pulse is disclosed. The system includes a travelling wave or ring laser incorporating a gain medium with polarizing means for introducing substantially polarized radiation having a first polarization state into the travelling wave laser and output coupling means to substantially output couple radiation having an output polarization state from the travelling wave laser. The system further includes polarization changing means incorporated into the optical path of the travelling wave laser for changing the polarization of radiation having the first polarization state to a seeding polarization state, wherein radiation with the seeding polarization state seeds the gain medium, and radiation intensity modulation means for modulating the intensity of radiation in the travelling wave laser to vary the feedback of radiation into the gain medium, wherein the radiation intensity modulation means also modulates the radiation with respect to the output coupling means.