Broadband and high-pass filtering based on city-wall-shaped MIM waveguide structure

In this paper, broadband high-pass filtering based on a metal-insulator-metal (MIM) waveguide structure with surface plasmon polaritons is proposed, which is composed of a city-wall-shaped waveguide and five coupled rectangular cavities. The city-wall-shaped waveguide allows long-wavelength light to pass through while suppressing the transmission of short-wavelength light. Further, by coupling multiple rectangular cavities, the suppression of short-wavelength light can be significantly enhanced, thereby achieving broadband high-pass filtering. The minimum transmittance of the passband is 0.85, and the edge steepness of high-pass filtering can reach 7.43 × 10⁻³/nm. Then, BK-7 standard optical glass with Kerr effect is introduced into the structure, so that the cutoff wavelength can be adjusted by external light irradiance, and tunable filtering with a tuning sensitivity of 26 nm μm²/W can be obtained. This broadband high-pass filtering structure with outstanding properties may be applied to optical communications and signal processing in integrated optical paths.