Surface second-harmonic generation based on periodically poled LiNbO ₃ nonlinear optical crystal

Abstract

We have generated a second-harmonic generation (SHG) of a Q-switched microchip Nd:YAG laser on the surface of a periodically poled LiNbO 3 (PPLN) nonlinear crystal near the grazing incidence angle. Three individual SHG waves as transmitted homogeneous, inhomogeneous and reflected radiations have been generated and their intensities are measured and characterized within a desirable range of about 10 different incidence angles of the Nd:YAG laser as pump source on the PPLN surface. The basic of surface nonlinear radiation is also investigated and similar results are calculated and extracted from the theory. Comparison between calculated and measured data shows that they are in good agreement with each other.

Second harmonic generation of metal nanoparticles under tightly focused illumination

“…Hence, the SHG usually arises from the surface of metal nanoparticles, where centrosymmetry is broken. [13] Compared to the linear response, it has been experimentally demonstrated that SHG is more sensitive to the metal nanostructure shape. [14] We have already investigated the SHG of centrosymmetric dielectric nanoshperes excited by tightly focused linearly polarized beams [15] or cylindrical vector beams [16] in the frame of the nonlinear Rayleigh-Gans-Debye (RGD) theory [17] when the incident field is not significantly perturbed by particles of low refractive index contrast.…”