Absorbing coating in the terahertz part of spectrum

Absorption of electromagnetic radiation in the frequency range of $35$ to $55$ THz by the multilayer coating, in which the top layer contains an array of pyramids arranged in a strictly geometric pattern in two mutually perpendicular directions is investigated. It is shown that the proposed structure provides a return loss better than $39.5$ dB at the resonance frequency of $42.3$ THz and a change of temperature of the sensitive layer of $3$ mK at the input power density of radiation of $0.1$ W/m$^2$.