Takashi KONDO,¹ Fumiaki AKASE,² Masashi KUMAGAI² and Ryochi ITO¹

¹Department of Applied Physics, Faculty of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113 Japan, ²Materials Development Research Laboratories, Japan Energy Co., Ltd., 3-17-35 Niizo-Minami, Toda, Saitama, 335 Japan

(Received December 16, 1994; Accepted January 27, 1995)

Linear and nonlinear optical properties of racemic (±)2-(α-methylbenzylamino)-5-nitropyridine ((±)MBANP) single crystals have been comprehensively investigated and compared with those of the enantiomorph (−)2-(α-methylbenzylamino)-5-nitropyridine ((−)MBANP) crystals. (±)MBANP crystal exhibits very high chemical and physical stability, but relatively small nonlinear optical coefficients (d₃₁=6.8 pm/V, d₃₂=4.7 pm/V,d₃₃=0.84 pm/V). A comparison between the nonlinear optical coefficients of (±)MBANP and (−)MBANP demonstrates the validity of the oriented-gas model in molecular crystals that neglects all the contributions from intermolecular interaction.

Key words : organic crystal, racemic form, second-harmonic generation, refractive index, nonlinear optical coefficient, crystal structure, oriented-gas model