Tuning infrared emission from microstrip arrays

Abstract

Earlier work has shown that a narrow-frequency-band, wide-angle emission is produced by an array of metal patches supported on a thin dielectric layer covering a ground plane. The modes responsible for this emission are local plasmons trapped under the metal patches. As the dielectric layer thickness, hd, is increased, the resonant emission fades in strength because the plasmon modes can no longer be trapped under a single patch. Further increases in hd, making it comparable to the light wavelength in the dielectric layer, lead to a collection of new emission peaks. These are narrower than the one peak found for small hd but they are not well separated. We have found that some of these peaks can be suppressed over a narrow range of hd. This leaves one with well-separated, narrow-band emission peaks. We have identified the physical mechanism for this selective suppression of emission peaks.