Study on micro-crystallization, growth, optical properties and defects of a nonlinear optical crystal: MnHg(SCN)4

High optical quality single crystals of a nonlinear optical material, manganese mercury thiocyanate, MnHg(SCN)4 (MMTC), with dimensions up to 21×14×13 mm3 have been grown by the solvent evaporation method. The growth habit of MMTC crystal crystallized under different conditions was investigated by means of micro-crystallization method. Two typical growth morphologies of the crystal were indexed and compared with the morphology deduced from the single crystal structure data. The results show that two novel {1 0 0} and {1 1 2} facets appear during the crystal growth. Powder second harmonic generation and spectral transmittance measurements were also performed. The results indicate that MMTC is phase-matchable and the UV transparency cutoff occurs at 373 nm. Various defects were found in MMTC crystal. Their formation mechanisms and the methods to eliminate these defects are discussed.