Thermally stable high-gain photorefractive polymer composites based on a tri-functional chromophore

We report on the photorefractive properties of thermally stable polymer composites based on the dye 2, $\mathrm{N,}$ $N$ -dihexylamino-7-dicyanomethylidenyl-3,4,5,6,10-pentahydronaphthalene. At an applied field of 50 V/μm, we have achieved a dynamic range of ${\text{Δn=8.5×10}}^{\text{−3}}$ and a net two-beam coupling gain of $\text{202\hspace{0.17em}}{\mathrm{cm}}^{\mathrm{-1}}.$ The diffraction efficiency peaks at an applied field of 28 V/μm, giving an external diffraction efficiency of 71%.