Benzofuran-terminated infrared dyes and their electro-optic properties in guest-host polymers

Molecular first hyperpolarizabilities and dipole moments of new benzo-fused dyes were calculated using quantum-mechanical density functional theory (DFT). Two new infrared dyes were synthesized: each one was terminated with 6-diethylaminobenzob]furan on one end, and with CF₃-tricyanodihydrofuran on the other end. The midsection of the π-electron framework for one dye contained a morpholino-substituted cyclohexenylene unit, and the other dye contained an ethoxysiloxane-substituted cyclohexenylene unit. Guest-host films were deposited on ITO-glass and contact poled. Electro-optic coefficients (r₃₃) were measured at a wavelength of 1550 nm by the attenuated total reflection method and by a modified simple Teng-Man reflection method. The measured values of r₃₃ were compared with values estimated from a well-known model that employs the molecular properties of the dyes and the film poling parameters. Thermal stability and electronic absorption spectra of the dyes were measured.