Scalable 3D Micropillar Frequency Selective Devices for Low-Loss Terahertz Bandpass Applications

This study presents the feasibility of utilizing micropillar array as frequency selective devices (FSDs) that set a new benchmark in terahertz technology. Leveraging an advanced UV lithography process combined with precision metallization, our approach addresses the persistent challenges of traditional 2D fabrication methods, such as significant dielectric losses and limited scalability. This study examined the effects of varying pillar heights while maintaining a constant pitch of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$170\ \mu \mathrm{m}$</tex>. Samples with heights of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$40\ \mu \mathrm{m}, 61\ \mu \mathrm{m}$</tex>, and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$72\ \mu \mathrm{m}$</tex> were analyzed, demonstrating exceptional performance at 1 THz, achieving approximately 90% absorption (reflectance of 0.1) across all configurations. This innovation significantly advances terahertz bandpass filters for high-speed wireless communications and other terahertz applications.