Abstract

We invoke the term semiorganic to describe a new class of nonlinear optical compounds composed of part organic and part inorganic constituents. The recently reported crystal 1-arginine phosphate (LAP) is one such material where organic 1-arginine molecules form cations and crystallize with inorganic phosphate anions.¹ We present another type of semiorganic crystal where organic molecules attach as ligands to the inorganic metal salt. We have grown two semiorganic crystals: zinc tris (thiourea) sulfate [Zn(TU)₃SO₄]² and (4-nitropyri- dine-N-oxide) mercury chloride [(NPO)HgCl₂]. Good optical quality crystals were grown by slow evaporation from solution with dimensions typically ~5 mm on a side. We have carried out nonlinear optical characterization of these materials using degenerate four-wave mixing experiments with a doubled Q-switched Nd:YAG laser (λ = 532 nm) to determine the magnitude of the third-order nonlinear susceptibility x⁽³⁾. The preliminary results indicate that cobalt doped Zn(TU)₃SO₄ has a X⁽³⁾ of about twice that of CS₂. We have also observed a significant four-wave mixing signal in (NPO)HgCl₂. Both of these crystals show relatively high damage thresholds of up to 17 J/cm² with 8-ns pulses. Finally, we note that semiorganic crystals have great potential as nonlinear optical materials compared with organic crystals due to their ease of growth to relatively large dimensions, superior mechanical and thermal properties, high optical quality, and high damage thresholds.

© 1989 Optical Society of America