CRYSTAL-GROWTH AND CHARACTERIZATION OF NEW ORGANIC NONLINEAR-OPTICAL MATERIALS - 6-CYANO AND 6-NITRO-2,2-DIMETHYL-3,4-EPOXYCHROMAN

Two chiral organic nonlinear optical materials, (3S,4S)-(-)-6-cyano-2, 2-dimethyl-3,4-epoxychroman (1) and (3R,4R)-(+)-6-nitro-2,2-dimethyl-3 ,4-epoxychroman (2), have been grown into single crystals of cm(3-)siz e. Although both compounds crystallise in the orthorhombic P2(1)2(1)2( 1) space group, they are not isomorphous and their crystal packings ar e quite different. Angle tuned type II phase-matched second harmonic g eneration between 0.8 and 1.064 mu m has been evidenced, with effectiv e nonlinear coefficients d(eff) of 1 and 5 pm/V at 0.96 mu m for 1 and 2, respectively. These values are in agreement with those estimated i n the oriented gas model approximation using EFISH first order hyperpo larisability values (beta(0) = 2.6 and 4.0 X 10(-30) esu for 1 and 2, respectively). (C) 1998 Elsevier Science B.V. All rights reserved.