Patterns in two photon photo-emission images of light diffraction structures in wave guiding transparent thin films

We have studied the patterns in two Photon Photo Emission 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 Fraunhoffer diffraction to determine the relative amplitude of modes exited at the periphery of the film where the in- coupling occurred. The evolution of waves in the film was then calculated using Fresnel-Kirchoff of integration where diffracting structures served as the aperture and two dimensional attenuated Green's function describes the guided mode fields at the vacuum interface. We used the results from their analysis to compute the photo electron emission rate, which we 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 photo excitations and compared the electron micrographs to field based calculations where we found good agreement. (author)