Surface-enhanced second harmonic generation at GaAs-AI interface

The formulae of second harmonic generation at a nonlinear crystal-metal interface with a rectangular grating are presented. According to the nonlinear medium theory given by Bloembergen and Pershan, we have solved the Maxwell equations by means of the perturbation method in power of the surface roughness parameter. All formulae and calculation show that the surface-enhanced second harmonic generation arises from the resonant excitation of surface polaritons, which is true to the direct contribution of free waves. The signals of the surface-enhanced second harmonic generation have been measured at GaAs-Al interface with different grating periods and groove depths using a tunable TEA CO2 laser. The experimental results are in good agreement with the theoretical prediction.