Design of a low power optical limiter based on a new nanocomposite material incorporating silica-encapsulated phthalocyanine in Nafion

Abstract

We report on the design of a stable optical limiter in the low laser power regime based on the thermal variation of refractive index in a novel nanocomposite material. The optical material, chloroaluminium-phthalocyanine (ClAlPc), is embedded in SiO2-Nafion nanocomposite membrane (ClSNf) and its thermally induced nonlinear refractive index is characterized by the Z-scan technique with a low power cw He–Ne laser as the source. The value of nonlinear refractive index coefficient, n2, is found to be about 1.11 × 10−11 m2 W−1. The experiment is repeated with the dye doped in pure Nafion membrane (ClNf) and the results are compared with those of ClAlPc doped SiO2–Nafion nanocomposite membrane. The value of n2 is found to be 1.36 × 10−11 m2 W−1 and is larger than that of the ClAlPc embedded SiO2–Nafion nanocomposite membrane. The photostability of the dye-embedded membrane is studied by exposing the sample to cw He–Ne laser and monitoring its fluorescence emission intensity continuously. The samples are found to show large thermal lens effect and demonstrated to be good optical limiters in the low power regime. Whereas the optical properties of dye-doped Nafion appear to be slightly better than those of the dye embedded in silica and incorporated in Nafion, the latter is found to offer excellent photostability.