Third-order nonlinear optical properties of a new type of D-π-D unsymmetrical phenoxazinium chloride with resonance structures

A new series of unsymmetrical phenoxazinium chlorides, featuring a heterocyclic aromatic pi-bridge with dialkylamino donors, were evaluated in acetonitrile solution for third-order nonlinear optical properties at 532 nm using a Z-scan technique. The title compounds exhibit strong reverse saturable absorption and nonlinear refraction. The third-order nonlinear optical properties were obtained under nanosecond and picosecond laser beams. The nonlinear mechanism is revealed by the excited-state nonlinearity, as observed from a picosecond pump-probe response experiment for one of the compounds. They are potential nonlinear optical materials because they also have good solubility in polar solvents and good thermal stability. (C) 2011 Elsevier B. V. All rights reserved.