Multilayer THz Metasurface Bandpass Filter with PTFE and HDPE Dielectric Spacers

Terahertz (THz) metasurfaces enable subwavelength electromagnetic wave control, offering a path to compact and tunable filters for spectroscopy, sensing, and communications. Here, we present a simulation-driven design for a compact multilayer THz bandpass metasurface filter [1]. The 3D device geometry consists of a silicon substrate supporting a thin gold film perforated with subwavelength annular apertures, a high-transmittance dielectric spacer (PTFE or HDPE), and an aligned array of gold rings on top. This stack can be fabricated by depositing gold through annular masks, eliminating the need for lithographic etching of the substrate presented in our previous model [2].

Full-wave electromagnetic simulations (COMSOL) guided the design process, optimizing spacer thickness and geometric parameters. Simulated transmission spectra show that devices with either PTFE or HDPE spacers yield broad passbands with high transmission. The spectral peak position and shape remain largely invariant under minor geometric deviations, indicating a robust design. The enhanced transmission is attributed to constructive interference between waves reflected at multiple interfaces in the multilayer structure. The combination of a simple mask-defined architecture, material-dependent tunability, and tolerance to fabrication imperfections makes this metasurface filter a promising candidate for THz bandpass filtering, anti-reflection coatings, spectroscopy, and biosensing. This work highlights the effectiveness of computational design in advancing THz metasurface technologies.

Foundation

This work was supported by Grants No. 22rl-056 and 24AA-2J068 of the Higher Education and Science Committee of the RA MoESCS.

References
[1] G.-M. Li, et al. Terahertz bandpass and bandstop filter based on the babinet complementary metamaterials, Optics Communications 571, 130944 (2024).

[2] K. Simonyan, et al. Broadband THz metasurface bandpass filter/antireflection coating based on metalized Si cylindrical rings, Semicond. Sci. Technol. 39 095012 (2024).