Second-order nonlinear optical properties of an aromatic polyurea exhibiting optical transparency down to 300 nm

Abstract

We report here a new high performance organic polymer comprised of urea moieties for optical second-harmonic generation. The nonlinear d33 coefficient of aromatic polyurea consisting of nonlinear optical chromophores in the main chain, estimated by Maker fringe measurements was found to be approximately 15 times that of KDP crystals at 1.064 μm. The decay of second-order optical nonlinearity of poled polyurea films at ambient conditions was negligible and temporal study showed persistent optical nonlinearity at least 1000 h after poling. Aromatic polyurea films exhibited optical transparency down to ∼300 nm in UV region and optical transmission was greater than 99% from 350–2500 nm like conventional inorganic nonlinear optical materials. Aromatic polyurea is the first example of an organic nonlinear optical material showing optical transparency at such low wavelengths. The nonlinear efficiency transparency trade-off demonstrates aromatic polyurea to be a new promising organic material for nonlinear optics.