A New Angle on Second Harmonic Generation from a Small Hole in a Metal Film

Bethe's theory treats a subwavelength aperture in a metal film as the combination of a parallel magnetic dipole and transverse electric dipole. For linear optics, this gives the usual dipole transmission; however, for nonlinear optics, it is interesting to consider how these two components interact. While many works have studied the nonlinear harmonic generation for metal nanoapertures, here we show that the Lorentz force dominates the second harmonic generation by an order of magnitude at angled incidence where the generation is maximized. The angular dependence matches that of the magnetic and electric dipoles accounting for Lambert's cosine law. The theoretical analysis and numerical calculations agree well with past experiments.

Automated summary

The study applies Bethe's theory to analyze the transmission of a subwavelength aperture in a metal film, treating it as a combination of a magnetic dipole and electric dipole for linear and nonlinear optics. The research shows that at angled incidence, the Lorentz force dominates the second harmonic generation, and matches well with the angular dependence of the magnetic and electric dipoles.