Implementation of Terahertz High-Pass Filters Based on All-Metal Microstructures using Deep X-ray Lithography

A method for fabricating high-pass terahertz quasi-optical filters in the form of thick (up to 1 mm in thickness) self-bearing copper microstructures of subwavelength topology is described. This method is based on forming a high-aspect-ratio mask of SU-8 resist on a silicon wafer via deep X-ray lithography through a tungsten X-ray mask followed by electroplating a copper layer through the resistive mask. An example of a 212-µm thick structure with a cutoff frequency of 0.42 THz having the geometry of hexagon-shaped through-holes arranged on a triangular lattice is considered. The results of broadband THz characterization and electromagnetic analysis of the structure fabricated are presented.