Quadratic Nonlinear Optical Properties of Diva Crystal
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QUADRATIC NONLINEAR OPTICAL PROPERTIES OF DIVA CRYSTAL T. WADA, C. H. GROSSMAN, S. YAMADA, A. YAMADA, A. F. GARITOa) AND H. SASABE Frontier Research Program (RIKEN), Wako, Saitama 351-01, Japan ABSTRACT New organic nonlinear optical crystal : dicyanovinyl anisole (DIVA) has been grown from vapor by low pressure sublimation and from saturated solution by solvent evaporation. Crystallographic structure and quadratic nonlinear optical properties were investigated. Molecular orientation in DIVA crystal with space group P2 1 is favorable for the highest possible value of bulk phase-matchable coefficient. Both type I and type II phase matched second harmonic generation (PMSHG) were observed from naturally grown faces of single crystals. Efficient PMSHG was achieved at a fundamental wavelength of 812 and 1064 nrm The efficient type I PMSHG coefficient was determined as deff = 4.9 x 10- esu = 40 x (d11 of a-quartz) at a wave.LH length of 1064 nm. Blue light generation was demonstrated by both PMSHG and sum-frequency mixing of the 812 nm laser with 1064 nm. INTRODUCTION Organic molecules which have conjugated 7r-electron systems exhibit various photoresponses: photoconductive, photovoltaic, photocatalytic behavior, and so on. Nowadays remarkable interest has been focused on organic single crystals because it has been found to posses unique opto-electronic properties in a crystalline state, such as ultrafast electron motion in polydiacetylene crystals, superconductive phenomena in charge transfer complexes and large second order nonlinear optical effects in intramolecular charge transfer compounds.
It
has been established
experimentally
and
theoretically that organic intramolecular charge transfer compounds have anomalously large optical nonlinearity (1] and show ultrafast response [2). After the demonstration of the powder test by Kurtz et al., a large number of organic molecules have been found to possess second order optical nonlinearity. However, only a few of them, for example 2-methyl-4-nitroaniline, urea, methyl-(2,4-dinitrophenyl)-aminopropanate (MAP), N-(4-nitorophenyl)(L)-prolinol and 3-methyl-4-nitropyridine-1-oxide (POM), could be crystallized in high quality and investigated on phase matched second harmonic generation (PMSHG) properties. Systematic ideas of molecular design have succeeded to some degree in the enhancement of microscopic second order nonlinear optical susceptibility (,8). On the other hand, molecular orientation in the crystalline state significantly influences the macroscopic second order susceptibility. Several approaches have been taken to control the molecular orientation; from the chemistry side, chemical modification was applied, such as introducing steric hindrance, hydrogen bonding, a chirality etc. and/or reducing the electrostatic dipole-dipole interaction; from the physics side poling techniques were applied to align nonlinear optically active molecules in polymer matrix. However, crystal engineering of organics is untouched area and lack of knowledge for crystal growth and crysta
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