Design, physics, and applications of photorefractive polymers

Abstract

The subject of this dissertation is design, physics, and applications of organic photorefractive polymers which are a recently discovered new class of multifunctional polymeric composites suitable for real-time holographic recording. Design principles of amorphous guest-host photorefractive polymers are described, and their performance is investigated. Also, the use of these materials as recording media in dynamic holographic applications is evaluated. Diffraction efficiency of η ∼ 86%, limited only by absorption and reflection losses, two-beam coupling net gain coefficient of Γ = 200 cm⁻¹, and light-induced refractive index modulations as high as Δn =7x10⁻³ are demonstrated. Hologram growth rates of the order of 500 ms are observed with recording light intensities > 10 mW/cm² using either low-power laser diodes (675 nm) or a HeNe laser (633 nm). The materials have been synthesized that show good sensitivity in red and near-infrared part of the light spectrum. Physical mechanisms leading to high performance of photorefractive polymeric composites and the influence of the polymer composite structure on optical performance are investigated. The experimental results are compared with a phenomenological model based on Kukhtarev's equations. Experiments showing possible applications of PR polymers, such as dynamic time-average interferometry and document security verification are demonstrated.