A chirp-compensated, injection-seeded alexandrite laser

A Q-switched alexandrite laser suitable for high-resolution spectroscopy is described which produces pulses of 35 mJ energy in a 10 MHz bandwidth, wit h a high-purity TEM00 mode. The laser can be synchronised to external event to within 100 ns. The output pulse length is 120 ns and the repetition rat e 25 Hz. The laser is injection-seeded by a Ti:sapphire laser operating aro und 730 nm. to preserve single-mode seeding under external triggering condi tions, and to obtain small time-jitter, active cavity length control was us ed. In order to achieve the 10 MHz output bandwidth, intra-cavity electro-o ptic modulators were used to compensate for the frequency chirp. The refrac tive index of;alexandrite was found to vary linearly with inversion density with a constant of proportionality equal to 1.6 x 10(-24) cm(3). In pulsed operation at 730 nm, the index change due to this effect is only partially compensated by changes due to ground state phonon relaxation.