HighTg, Nonpoled Photorefractive Polymers

Abstract

Room-temperature photorefractivity without prepoling was demonstrated in polymers and copolymers with a glass transition temperature well above 100 °C. The compounds used are multifunctional side-chain polymers exhibiting chiral, semiconducting, photochromic, and nonlinear optical (azoaromatic moieties) properties. The photorefractive performance was linked to the reorientational effect of the photogenerated space-charge field, which well below the glass transition temperature can be active in the presence of the conformational mobility achieved via the trans−cis light-induced isomerization. The grating build-up time, which is long at λ = 633 nm (with a time constant τ ≈ 500−1000 s) decreases by 2 orders of magnitude at λ = 532 nm, where absorption is higher.