Mid‐infrared transmission through a subwavelength circular aperture coupled to a surrounding concentric metal grating by surface plasmon excitation

Abstract

AbstractSurface plasmon polariton (SPP) coupling of mid‐infrared light to the electrons on the surface of a concentric metal grating integrated onto a GaSb substrate is simulated with 3‐dimensional finite difference time domain methods. The transmission through a subwavelength circular aperture at the center of the grating by this coupling is highly sensitive to the variation of the aperture diameter and shows the strongest SPP coupling when the diameter approximately becomes a half period of the grating. On the other hand, the simulation reveals that SPP coupling does not decay so fast for d larger than a half period and provides noticeable effects until the diameter becomes comparable to the grating period. It also shows that the coupling is ineffective when the diameter reaches a few grating periods. Transmission through the subwavelength aperture is remarkably enhanced by such SPP coupling, which can be very important in its practical applications. The simulation is focused on its application to mid‐infrared focal plane arrays. Some potential factors for additional enhancement of transmission are discussed. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)