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Processes that generate decay of polarization in a cross-linked, nonlinear optical polymer have been studied, and their relationship to a corresponding change in second-order nonlinearity ( ®) has been determined. Measurements of second-harmonic generation, thermally stimulated discharge current, and UV-visible absorbance have been employed to identify polarization decay resulting from relaxation of oriented molecular dipoles, migration of space charge, and chemical degradation of chromophores. The effect of process parameters on ® stability in these materials is observed and explained.

Novel difunctional nonlinear optical (NLO) azo compounds with exceptional thermal stability have been synthesized and incorporated into side-chain and cross-linked polymers. The nonlinear optical response of these polymers has been studied with second-harmonic generation and electrooptic measurements. Channel waveguide intensity modulators displayed an electrooptic coefficient of 13.1 pm/V.

A complete assignment of the six librational modes of the TCNQ0 crystal has been made employing both polarized Raman spectroscopic measurements and lattice dynamical calculations. Agreement between theory and experiment is good and modes at 40.5, 74.5, and 96 cm−1 are assigned as Ag active and those at 63, 75.5, and 104 cm−1 are Bg active. The lattice modes are found to be clearly separated from the molecular modes. The study emphasizes the importance of crystal optics and quality in the measurement of the polarized Raman spectra of biaxial crystals.

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