Fabrication Of Broadband Absorbers For The Far-Infrared Spectral Range

A broadband electromagnetic wave absorber is presented which spans far-infrared regime. This absorber is non resonant and utilizes silicon micromachining techniques. The structure is made of a doped silicon wafer whose surface is etched anisotropically to form a two-dimensional array of inverse pyramid cavities. Far-infrared waves incident onto this structure undergo multiple reflections by the slanted walls and the energy of the incident waves is partially absorbed by the wall at each reflection, and eventually fully dissipated therein. The absorbance of the structure is at least 90% across the far-infrared hand from 1.25 to 5.00 THz, and can be further extended with a thicker substrate.