Injection seeding of a high-energy Cr:LiSAF ring laser by a narrowband diode-pumped Cr:LiSAF microlaser

High spectral purity, high energy, tunable laser sources operating in the absorption bands at 730, 815 or 940 nm bands are required for remote sensing of water vapor mixing ratio with a differential absorption lidar. For this application, injection seeding of a high energy Cr³⁺:LiSeAlF₆ ring laser with a narrowband, Q- switched, Cr:LiSAF laser was investigated. The slave ring laser utilized either a flashlamp pumped or diode-pumped Cr:LiSAF gain module. The flashlamp pumped module provided a single-pass gain of 1.5 at 825nm. The diode-pumped module consisted of a Cr:LiSAF rod, side-pumped with high power diode bar stacks giving > 150mJ energy in 200 microsecond(s) pulse. The spectral bandwidth of the ring laser output was 8 to 10 nm without injection seeding. The seed Cr:LiSAF laser was end pumped by a fiber coupled diode laser, and tuned with a birefringent filter. Tuning from 810 to 980 nm was possible with two sets of mirrors, and 160 to 700 ns long Q- switched pulses, with up to 40(mu) J energy, at 1000 Hz, were obtained with linewidths of < 0.1 nm. Successful seeding of both diode and flashlamp pumped lasers, narrowing of ring laser linewidth to < 0.1 nm, and 16 mJ/pulse output have been achieved.