Laser diode array pumped Yb:YAG/BIBO 515 nm thin disc laser with four-pass optical coupling system

We presented a new simple flat-concave cavity system to produce compact and low-cost 515 nm laser, and the validity has been demonstrated. The Yb:YAG crystal with 10% concentration was 300 μm thickness and 10 mm in diameter. The four-pass optical coupling system was well designed with two spherical imaging mirrors (ϕ = 30 mm, R = 50 mm). Taking into account mode matching, the pump-spot radius in the laser crystal was calculated by LightTools software. The 2 × 2 × 1.5 mm³ BIBO crystal cutting at a type-I phase-matching direction of (θ, φ) = (166.8°, 90°) was employed. With 4.4 W incident power, the maximum output power of 14.3 mW at 515 nm was obtained without optimization of soldering technique, and the single-frequency phenomenon was first observed when the output power was 3 mW.