Polycrystal Synthesis, Crystal Growth, Structure, and Optical Properties of AgGaGenS2(n+1) (n = 2, 3, 4, and 5) Single Crystals for Mid-IR Laser Applications

AgGaGenS2(n+1) crystal is a series of quaternary nonlinear optical materials for mid-IR laser applications of converting a 1.064 μm pump signal (Nd:YAG laser) to 4–11 μm laser output, but only AgGaGeS4 has attracted the most attention, remaining the other promising AgGaGenS2(n+1) crystal whose physicochemical properties can be modulated by n value. In this work, AgGaGenS2(n+1) (n = 2, 3, 4, and 5) polycrystals are synthesized by vapor transport and mechanical oscillation method with different cooling processes. High-resolution X-ray diffraction analysis and refinement have revealed that all the four compounds are crystallized in the noncentrosymmetric orthorhombic space group Fdd2, resulting in the excellent nonlinear optical property, and the distortion of tetrahedron with the variation of n value causes the discrepancy of physicochemical property. Besides, using the modified Bridgman method, AgGaGenS2(n+1) single crystals with 15 mm diameter and 20–40 mm length have been grown. We have discussed the str...