High performance photorefractive molecular glass composites in reflection gratings

Reflection grating photorefractivity of molecular glasses of novel star-shaped molecules end-caped with carbazole moiety, α,α′,α″-tris-(4-(carbazoryl)-n-hexyloxyphenyl)-1,3,5-triisopropylbenzene (Tris) and α,α,α′,α′-tetrakis-(3,5-dimethyl-4-(6-carbazoryl-n-hexyloxy)phenyl)-p-xylene (Tetrakis) is presented. Large asymmetric two-beam coupling (asymmetric energy transfer) was achieved in reflection grating geometry. Highest net gain coefficient of 33 cm−1 with optical gain of 53 cm−1 and absorption coefficient of 19.7 cm−1 was obtained for Tetrakis composite at applied electric field of 57.7 V/μm. Effective large trap density is associated with high photorefractive optical gain.