Optical limiting characteristics of platinum and gold nanoparticles based on thermal nonlinear refraction

In this work, the platinum and gold nanoparticles colloids are fabricated by 18 ns pulsed laser ablation of pure platinum and gold plates in the distilled water. The formation of the nanoparticles has been evidenced by taking the UV-Vis absorption spectrum and observing the surface plasmon absorption band of gold and platinum nanoparticles as well as by transmission electron microscopy.The nonlinear optical properties of the platinum and gold nanoparticles in distilled water are measured by the closed- aperture Z-scan technique under exposure to a low- power continuous-wave laser at a wavelength of 532 nm. The observed asymmetric nature of the Z-scan measurements along with the fact that the laser light is CW suggests that the origin of the nonlinear refractive index is thermo-optic. The optical limiting performance of the platinum and gold nanoparticles are characterized by exposure to CW laser operating at a wavelength of 532 nm. The results show that nonlinear self-defocusing effect increases the performance of the optical limiting. The engineering of the experimental geometry can accomplish the tunability of the limiting threshold of optical limiters.