Second Harmonic Generation from Plasmon-Polariton Excitation on Silver Diffraction Gratings : Comparisons of Theory and Experiment

We present a comparison between experimental and theoretical results for the diffraction efficiencies of the second-harmonic light produced in the orders of silver diffraction gratings. The gratings considered are sinusoidal, have depths of a few nanometers, and can produce significant surface plasmon polariton excitation at fundamental and second-harmonic frequencies. The calculations are based on a general expression for the nonlinear polarization of the surface of a homogeneous and isotropic medium, and the diffraction problems at the fundamental and harmonic frequencies are solved using a Rayleigh method. The silver gratings were fabricated using holographic lithography and evaporative metal deposition techniques. The samples were illuminated with picosecond pulses of wavelength 1064 nm and photon-counting techniques were used to study the diffracted orders at 532 nm, with absolute normalization provided by a quartz reference. The diffracted orders exhibit anomalies and other features, many of which are related to plasmon polariton excitation at both fundamental and second-harmonic frequencies. Employing previously measured values for the nonlinear susceptibilities of a flat silver surface, remarkably good comparisons of theory and experiment are obtained for the second harmonic order efficiencies