Ellipsometric determination of the electric-field-induced birefringence of photorefractive dyes in a liquid carbazole derivative Original Research Article

We have used ellipsometric measurements on solutions of 2-dihexylamino-7-dicyanomethylidene-3,4,4a,5,6-pentahydronaphthalene and related polyenes in liquid 9-(2′-ethylhexyl)carbazole to measure the electric-field-induced birefringence at wavelengths of 690 nm and 830 nm. This electric-field-induced birefringence is related to the product of dipole moment squared and the polarizability anisotropy, μ2Δα, and to a large extent determines the dyeʹs photorefractive figure-of-merit (FOM). We show that μ2Δα increases with the conjugation length and report one of the highest μ2Δα values observed so far.