Gold (Au) colloidal nanoparticles (NPs) have been synthesized by direct irradiation of gold precursor (HAuCl 4 ) solution in polyvinyl alcohol (PVA) matrix using nanosecond laser pulses at different irradiation fluencies and exposure times. Appearance of wine and dark wine colors indicated the formation of Au NPs. Transmission electron microscope (TEM) images exhibited spherical shaped particles and X-ray Diffraction (XRD) pattern confirms polycrystalline nature of Au NPs with cubic structure.

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... u NPs displayed negative nonlinearity and exhibited a shift from saturable absorption (SA) at lower intensities to reverse saturable absorption (RSA) accompanied by nonlinear scattering at higher excitation intensities in nanosecond regime at 532 nm. Two-photon absorption (TPA) is attributed to be responsible for the RSA behavior. He has been working on synthesis of metal and metal alloy nanoparticles for the application of optical limiting studies. His work also includes in the fabrication of waveguide structures in rare earth doped glasses using femtosecond laser direct writing. K. Shadak Alee is a Ph.D. student of School of Physics from University of Hyderabad in India. He has been working on linear and nonlinear optical properties of 3D colloidal photonic crystal structures and formation of different sizes of metal nanoparticles using laser irradiation for surface enhanced Raman spectroscopic (SERS) studies. D. Narayana Rao, Currently a Professor of Physics at the University of Hyderabad, obtained his Ph.D. in Physics from IIT Kanpur. He has been working in the field of lasers and nonlinear optics for the last three decades. He has published nearly 150 papers in international journals. His current interests are optical limiting, photonic crystals, femtosecond laser direct writing, spectral interferometry, NLO studies of organic, inorganic and semiconductor nanoparticles. metal nanoparticles by pulsed laser ablation of a solid-state metal target immersed in a liquid.