Enhanced optical nonlinearity in β-MnO₂ nanowire network decorated with Ag nanoparticles

We report on enhanced nonlinear optical absorption and optical limiting in β-MnO₂ sponge-like nanowire network decorated with Ag nanoparticles excited by nanosecond laser. A simple two-step process is used to prepare the samples. The structure, morphology and the elemental analysis of the prepared samples are studied using x-ray diffraction, field emission scanning electron microscopy and energy-dispersive x-ray spectroscopy. Nonlinear optical absorption properties of the samples in solution is studied using the open aperture Z-scan technique employing 5 ns laser pulses at 532 nm. Nonlinear transmission measurements show that β-MnO₂ exhibit weak saturable absorption at low fluence and large optical limiting at high fluence, while upon decoration with Ag particles, Ag/β-MnO₂ shows strong saturable absorption at low fluence and enhanced optical limiting at higher fluence with an optical limiting threshold value three times lower than that of bare β-MnO₂ nanowires. The results indicate that these materials are potentially useful for constructing saturable absorbers and optical limiters.