Patterns in Two Photon Photoemission Images of Light Diffracting Structures in Wave Guiding Transparent Thin Films

Abstract

We have studied the patterns in two photon photoemission images of light diffracting structures in wave guiding transparent thin films. We first determined the wave numbers of guided modes that can be expected in dielectric thin films, then used Fraunhofer diffraction to determine the relative amplitude of modes excited at the periphery of the film where the in-coupling occurred. The evolution of waves in the film was then calculated using Fresnel-Kirchhoff integration, where the diffracting structure served as the aperature and a two dimensional, attenuated Green’s function describes the guided mode fields at the vacuum interface. We used the results from this analysis to compute the photoelectron emission rate, which derived from the complex sum of surface fields and incident light. We studied two photonic structures in an aberration corrected photoemission electron microscopy using two photon excitation and compared the electron micrographs to field based calculations, where we found good agreement.