This paper presents several ultrathin multi-band terahertz bandpass filters (BPFs) based on metal-dielectric-metal (MDM) metasurfaces, achieving independently tunable multi-band transmission characteristics through parametric adjustment of the geometric parameters (side length w, gap spacing \(\varDelta s\) , and loop count N) of the square-loop arrays. The designed tri-band filter is primarily analyzed for its excellent performance at 0.72/1.23/2.23 THz, including a roll-off rate >30 dB/THz, average transmittance of 97% (peak insertion loss \(< -0.10\) dB), and out-of-band rejection ratio >25 dB. The multi-band spectral response is validated via finite integration technique (FIT) simulations in CST Microwave Studio, combined with surface electric field distribution analysis and effective medium theory (EMT) to elucidate the propagation mechanism of THz waves and the functional roles of each structural layer. A systematic investigation of geometric parameter dependencies on transmission performance is also conducted. The designed BPF exhibits potential applications in electromagnetic interference suppression, ultrasensitive biosensing, and dynamic THz signal multiplexing, owing to its multi-band transmission, polarization insensitivity, and compact footprint.
