Present review examines the basic physical principles of operation of terahertz radiation filters. The main types of filters are presented, namely, based on absorbing/scattering materials, metamaterials (frequency-selective surfaces), interference, polarization, and some exotic types. The basic principles of calculating the filters transmission based on matrix methods are described, as well as based on solving Maxwell's equations. The areas of application of THz filters are listed.

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Keywords: THz, cutoff filters, high-pass filters, band-pass filters, notch filters, absorption, metamaterials, frequency-selective surface PACS: 07.57.−c, 42.25.Ja, 42.81.Gs (all) DOI: 10.3367/UFNe.2025.11.040059 URL: https://ufn.ru/en/articles/2026/2/e/ Citation: Kaveev A K, Kropotov G I "Physical principles of filtration and the design of terahertz radiation filters" Phys. Usp. 69 (2) (2026) Received: 16th, March 2025, revised: 9th, November 2025, accepted: 11th, November 2025 Оригинал: Кавеев А К, Кропотов Г И «Физические принципы фильтрации и устройство фильтров терагерцового излучения» УФН 196 182–204 (2026); DOI: 10.3367/UFNr.2025.11.040059