2ND-HARMONIC LIGHT GENERATION IN PYROELECTRIC LIQUID-CRYSTAL POLYMERS

Pyroelectric Liquid-crystal polymers were prepared by photopolymerizat ion of binary mixtures of two monomers that exhibit a smectic C phase : A2c, R)-(-)-2-[(10-acryloyloxy)decyl]oxy}-3-nitrophenyl 4-{4'-[(11-a cryloyloxy)undecyloxy]phenyl}benzoate and A1b, 4''-((R)-(+)-2-octyloxy )-3''-nitro phenyl 4-(4'-[(11-acryloyloxy)undecyloxy]phenyl) benzoate. Both liquid-crystal monomers have a NO2 substituent to enhance the no nlinear optical properties, and one of the monomers, A2c, permits poly merization to a cross-linked polymer. During the polymerization an ele ctric held of approximately 25-50 V/mu m was applied over the ferroele ctric liquid-crystal cells. All cases of polymers formed from the chir al smectic C phase showed a second-harmonic-generated signal with no external field present, indicating that polar order became fixed. The orientation dependence of the second-harmonic-generated intensity was similar to that of the ferroelectric Liquid-crystal monomer; however, some changes were observed that might be due to changes in the dielect ric axes of the system. The highest d(16) and d(23) coefficients were found to be in the range 0.65-0.8 pm/V and differed depending on the d etailed preparation of the sample. Experimental results of several pol arization combinations of the pump and frequency-doubled light are pre sented and discussed. (C) 1998 Optical Society of America.