HighT_g, Nonpoled Photorefractive Polymers

Abstract

Room-temperature photorefractivity without prepoling was demonstrated in polymers and copolymers \nwith a glass transition temperature well above 100 °C. The compounds used are multifunctional sidechain \npolymers exhibiting chiral, semiconducting, photochromic, and nonlinear optical (azoaromatic \nmoieties) properties. The photorefractive performance was linked to the reorientational effect of the \nphotogenerated space-charge field, which well below the glass transition temperature can be active in \nthe presence of the conformational mobility achieved via the trans-cis light-induced isomerization. The \ngrating build-up time, which is long at λ ) 633 nm (with a time constant τ ≈ 500-1000 s) decreases by \n2 orders of magnitude at λ ) 532 nm, where absorption is higher.