Poly(silane)-based high-mobility photorefractive polymers

The photorefractive (PR) properties of guest-host polymer systems composed of the high-mobility chargetransporting host polymer poly(4-n-butoxyphenylethylsilane) (PBPES), a nonlinear dopant, and a sensitizer are characterized br four-wave mixing (FWM) and two-beam coupling (2B0). Steady-state diffraction efficiencies as high as 10^-4 (λ = 753 nm, E₀ = 16 V/μm; sample thickness, 175 μm) and rise times as short (λ = 647 as 39 nm, E₀ = 11.4 V/μm, 1-W/cm² intensity) are observed by FWM; to our knowledge this is the fastest response observed in a PR polymer to date. In addition, net 2BC gain was observed in one material combination. The mobilities of PBPES and a mixture consisting of PBPES:Coumarin-153:C₆₀ are measured, and the mobility of the latter is ˜10^-4 cm²/(V s) at E₀ = 10 V/μm, a factor of 10 larger than that of the undoped polymer. The rate of grating growth is analyzed within a charge-generation-limited model. The evidence indicates that carrier mobility is not the limiting factor in the PR response of these materials.