Designer Infrared Filters Using Stacked Metal Lattices

摘要

The authors have designed and fabricated infrared filters for use at wavelengths greater than or equal to 15 microns. Unlike conventional dielectric filters used at short wavelengths, these are made from stacked metal grids spaced at a very small fraction of the performance wavelengths. The individual lattice layers are gold, the spacers are polyimide, and they are assembled using integrated circuit processing techniques, They resemble some metallic photonic band-gap structures. The authors simulated the filter's performance, including the coupling of the propagating near-field electromagnetic modes, using computer-aided design codes, and found no anomalous absorption. The geometrical parameters of the grids are easily altered in practice, allowing for the production of tuned filters with predictable and useful transmission characteristics. Although developed for astronomical instrumentation, the filters are broadly applicable in systems across infrared and terahertz bands.