Possibility of changing the duration of pulses emitted by a mode-locked laser by the use of a birefringent crystal plate

A method was developed for varying continuously the duration, carrier frequency, and width of the emission spectrum of a mode-locked laser. The method was based on the use of a polarization filter. A reduction of the width of the spectrum to 3 Å did not increase the minimum (10^–11 sec) pulse duration but simply increased the stability of the laser operation. Further narrowing of the spectrum to 0.5 Å increased the pulse duration to 50 psec.