Nd:YAG/V:YAG microchip laser

Abstract

Two passively Q-switched Nd:YAG monolithic microchip laser devices were prepared by Nd:YAG and V:YAG crystals diffusion bonding. Stable generation of nanosecond pulses at wavelength 1338nm was obtained. The first laser, designed for higher mean pump and output power, was based on the monolith crystal which combines in one piece a 4mm long cooling undoped YAG crystal, 12mm long active laser part (YAG crystal doped with Nd³⁺ ions), and 0.7mm long V³⁺:YAG saturable absorber. The second one was designed to obtain shorter pulse length. It consists of 4mm long Nd:YAG laser crystal and 0.7mm long V³⁺:YAG saturable absorber. The diameter of both crystals was 5 mm. The initial transmission of the V:YAG part (T₀ = 85%) and the laser resonator was the same in both crystals. Laser mirrors were deposited directly onto monolith faces. The output coupler with reflection 90% for the generated wavelength was placed on the V³⁺-doped part. The pump mirror (HT@808 nm, HR@1.3 μm) was placed on opposite monolith face. Both microchip lasers were tested under longitudinal diode pumping. The pulse length was stable for all regimes for both crystals. For longer crystal it was equal to 6.2 ns, for the shorter one it was 1.7 ns (FWHM). The wavelength of linearly polarized TEM₀₀ laser mode was fixed to 1338nm for longer crystal. In case of shorter crystal some instabilities were observed for higher mean pump power. The pulse energy depends on the mean pump power. For pulsed pumping with low duty factor the output pulse energy was equal to 131 μJ for longer crystal, and 34 μJ for shorter crystal. This corresponds to peak power 21kW and 20kW, respectively. In CW pump regime the pulse energy was 37 μJ for longer crystal (peak power 6 kW), and 16 μJ for shorter one (peak power 9.4 kW).