Experimental Demonstration of a Low-Pass Spatial Filter Based on a One-Dimensional Photonic Crystal with a Defect Layer

It is predicted theoretically that a one-dimensional photonic crystal (PC) with a defect layer has an incident-angle dependent transmittance. Growing a multilayer of this PC structure on a BK7 glass substrate by means of thermal vacuum evaporation, we have experimentally measured its transmittance at near-infrared wavelength. The measured transmittance are in good agreement with the theoretical prediction if the influence of random errors in the layer thicknesses resulting from the deposition process is excluded. This work suggests that a one-dimensional PC with a defect layer can be fabricated as a two-dimensional near-field low-pass spatial filter.