Role of temperature in controlling performance of photorefractive organic glasses

We present a detailed temperature-dependence study of dielectric, birefringent, conductive, and photorefractive (PR) properties of high-performance low-molecular weight organic glasses that contain 2 dicyanomethylene 3-cyano-2,5-dihydrofuran (DCDHF) derivatives DCDHF organic glasses sensitized with C-60 exhibit high two-beam coupling gain coefficients in the red-wavelength region. However, in the best performing DCDHF glasses at room temperature the PR dynamics are limited by slow molecular reorientation in the electric field. While orientational and therefore PR speed can be significantly improved by increasing the temperature above the glass transition temperature of the material, the steady-state performance may worsen. Comprehensive study of the temperature dependence of various processes, which contribute to the PR effect in DCDHF glasses, clarifies the limiting factors and allows for optimization of the overall PR performance.