Chirp in picosecond film lasers and pulse compression by linear dispersion in optical fibers

Time-averaged and time-resolved spectra of single-mode, optically pumped, ultrashort-cavity semiconductor film lasers have been studied in detail. The time-averaged spectra are broad (3-17 nm). Time-resolved spectra show that the lasing wavelength increases (chirps) during the picosecond-time-scale duration of the pulse. The chirp is due to free-carrier plasma effects on the refractive index of the highly excited semiconductor (10(20) carriers/ cm(3)). Film-laser pulses are compressed by a factor of 2 in an 8-m length of single-mode optical fiber because of the linear group-velocity dispersion of the fiber, producing a pulse of 3.7-psec duration at 1.264 microm.