Compact Efficient 2.1- $\mu $ m Intracavity MgO:PPLN OPO With a VBG Output Coupler

We present a compact efficient intracavity MgO:PPLN optical parametric oscillator (OPO) with a volume Bragg grating output coupler pumped by a Q-switched Nd:YVO
₄
laser operating in 2.1-μm region. Narrowband 2.1-μm output power of 3.7 W is achieved with a pulse duration <;2 ns at 15-kHz repetition rate. A maximum conversion efficiency of 19.5% from laser diode (LD) to 2.1 μm is obtained at 17.5-W LD pump power. The 2.1-μm beam quality factors M
²
of 1.85 and 2.37 in horizontal and vertical directions are obtained. To the best of our knowledge, the efficiency is the highest ever achieved from an intracavity OPO in 2-μm region.