Diode-side-pumped monolithic Nd:YAG slab laser

Abstract

Compact, high-efficient, side-pumped monolithic Nd:YAG slab laser is presented. Designed active crystal shape ensures four internal reflections of generated laser radiation forming a ring resonator with high gain. A horizontal projection of the active medium form was a isosceles trapezoid with 18.6 mm long base, and 5 mm height. The angels between long base and legs are 87 deg. The thickness of the slab was 4 mm. Both base-sides and one leg-side was high reflective for lasing radiation. Second leg-side was partially reflective for lasing radiation and serves as an output coupler. The longer base-side was highly transparent for pumping radiation. The opposite base-side was highly reflecting for pump. To increase the pump absorption efficiency Nd-doping concentration was 1.4 % Nd/Y. As a pump source, single-bar quasi-cw fast-axis collimated laser diode JOLD-180-QPFN (Jenoptik) with peak power 180 W at 808 nm and output beam 10 0.9 mm without any further optics was used for slab side-pumping. The pumping pulses with repetition rate 5 Hz were 250 μs long (maximum pump energy 39 mJ). The Nd:YAG laser was operated at 1.06 µm. Two external mirrors (one totally reflecting, second with reflectivity 80 % at 1.06 μm) were used to form the oscillator. The laser was tested in the free-running regime. The maximum laser output energy reached was 5.9 mJ which corresponds to optical-to-optical efficiency of 15 %. The laser slope efficiency in respect to laser diode output was 20 %. The divergence of multimode output beam was 7 × 2.5mrad.