Abstract: A mode locked pulsed laser incorporates an intracavity element to compensate for the dispersion caused by other intracavity elements. This element reduces the tendency of the pulse to broaden in the cavity due to group velocity dispersion and results in very short pulses. In the laser of the present invention, mode locking is initiated by detecting the beat frequency between adjacent longitudinal modes using a high speed photodiode. This signal is amplified and then the frequency is divided by two. The signal is passed through an electronically adjustable phase shifter and then to a power amplifier. This signal is applied to the acousto-optic modelocker. If the cavity length drifts the beat frequency between the longitudinal modes changes. The rf signal applied to the modulator changes in exactly the right manner to track the drift in cavity length. Thus the modelocker is automatically synched to the round trip of the laser cavity.

Abstract: A tunable solid state laser having a titanium:sapphire grain medium and a birefringent filter mounted within a resonant cavity is provided. The resonant cavity is longitudinally pumped. The cavity is enclosed in a casing which has a small window admitting the pump beam into the resonant cavity, and a small window with an anti-reflection coating allowing the laser output to exit the casing. The casing is maintained at a positive pressure of nitrogen gas during operation of the laser to purge the resonant cavity of air and water vapor.