Novel Elements of Terahertz Optics Based on Artificial Opal

Opal-like structures are proposed as a promising new material for terahertz (THz) optics. Opal matrices deposited from SiO 2 globules with a diameter of 300 nm with subsequent annealing in the temperature range 200–1500°C are investigated. It is experimentally shown that the THz optical properties of such a material can vary over a wide range with an increase in the annealing temperature (refractive index from 1.6 to 1.95, amplitude absorption coefficient of the material from 7 to 0.4 cm –1 ). On the basis of effective medium theory, namely the Bruggemann equation, a model is proposed that makes it possible to predict the optical properties of the material under study depending on the annealing temperature. To demonstrate the possibility of manufacturing an optical THz component, a plane-convex cylindrical lens is fabricated from the material under study. The possibility of varying the optical properties of the opal matrix in a wide range, a low absorption coefficient, and the absence of dispersion in the THz spectral region show the prospects of opal-like materials for THz applications.