A Tunable Low-Pass Filter Based on MIM Structure with Kerr Effect

In this paper, a tunable low-pass optical filter based on metal–insulator-metal (MIM) structure with surface plasmon polaritons (SPPs) is proposed and discussed, which is composed of a bus waveguide containing two silver rods with square section (SRSS) and two semi-elliptical resonators (SERs) partially filled with Kerr material. After optimizing the structural parameters, a relatively ideal low-pass filtering effect is achieved. The minimum transmittance of the passband is 0.76, and the roll off coefficient (ROC) of the filtering barrier is up to 1.55 × 10⁻⁷ GHz⁻¹. Furthermore, based on the influence of refractive index on optical modes in the two SERs, the cutoff frequency of the filtering effect can be conveniently adjusted by controlling the external light field irradiated on the Kerr material. The sensitivity of the right cutoff frequency adjustment is 11.6 GHz·μm²/mW, accompanied by an increase in the ROC. The low-pass filter with tunable cutoff frequency may have promising applications in integrated optical communication and information processing.