2ND-HARMONIC GENERATION FROM 2-ARYLIDENEINDAN-1,3-DIONES STUDIED BY THE POWDER METHOD

Derivatives of 2-benzylideneindan-1,3-dione with a variety of substituents (R) in the 2-benzylidene ring have been prepared, most of which exhibit good transparency in the spectral region above 500 nm. Their second-harmonic (SH) intensities have been measured by the powder method using a 1064 nm YAG laser. The derivatives with R = 4'-Me (4) and 4'-OH (7) have phase-matchable and relatively high SHG activity (in the range 50-100 x SHG activity of urea), which is stable below the melting point. With a change in crystallisation conditions such as solvent, temperature, or rate of crystal growth, the SHG activity and crystal morphology of 7 are substantially changed whereas those of 4 are not greatly affected. These different features are reflected also in their X-ray diffraction patterns.