3RD-ORDER NONLINEAR-OPTICAL PROPERTIES OF POLYMORPHS OF OXOTITANIUM PHTHALOCYANINE

Third-order nonlinear optical susceptibilities chi(3) of amorphous, al pha, beta, and Y polymorphs of oxotitanium phthalocyanine (TiOPc) meas ured by third-harmonic generation technique are reported. The chi(3)(- 3omega;omega,omega,omega) values of amorphous, alpha, beta, and Y poly morphs of TiOPc varied signifIcantly depending upon the crystal struct ures and measurement wavelengths. The chi(3)(-3omega;omega,omega,omega ) of alpha-TiOPc was found to be 5 times as large as that of beta-TiOP c and more than 2 times as large as that of Y-TiOPc at 2.1 mum. The al pha-TiOPc showed the largest chi(3)(-3omega:omega,omega,omega) of 1.59 x 10(-10) esu at 2.43 mum. The origin of third-order optical nonlinea rity in different polymorphs-is discussed in terms of molecular packin g of the TiOPc molecules that causes variations in the intermolecular interactions and hence affects optical nonlinearity.