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, $h_d$, is increased, the resonant emission fades in strength because the plasmon modes can no longer be trapped under a single patch. Further increases in $h_d$, 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 $h_d$ but they are not well separated. We have found that some of these peaks can be suppressed over a narrow range of $h_d$. This leaves one with well-separated, narrow-band emission peaks. We have identified the physical mechanism for this selective suppression of emission peaks.