Large-size high-quality CdSe-OPO component for far IR laser output prepared by directional crystal growth technique

CdSe crystals are one of the most potential far infrared (IR) nonlinear optical (NLO) materials due to their excellent overall performance. However, it is difficult to prepare a large-size and low absorption CdSe component, which limits laser output power. In this work, a CdSe crystal was grown using a capsuled Mo-crucible method to maintain a stoichiometric melt composition in the process of crystal growth. A high-quality CdSe crystal with the largest size to date of phi 40 x 100 mm(3) along the (100) direction was successfully obtained using this method combined with a seed directional technique. The as-grown CdSe crystal demonstrated low absorption coefficients of <0.005 cm(-1) at 2.05 mu m and 10.6 mu m, good crystallinity, and optical homogeneity. An 11 mm x 11 mm x 78 mm CdSe crystal element with theta = 73.5 degrees +/- 0.2 degrees, and phi = 0 degrees was fabricated to meet the requirement for type-II phase match (PM), the average idler output power of 1.8 W was obtained corresponding to a pulse energy of similar to 0.36 mJ at 10.2 mu m using signal-resonate optical parametric oscillator (SR-OPO) technology. Besides, the seed directional technique could provide reference for preparing other NLO crystals, and the capsuled Mo-crucible method could also be used to grow other chalcogenide crystals that have high melting points.