An Amplitude Tunable Dual-Band Bandpass Filter With Perfect Absorption and Its Sensing Applications

A design is presented here that integrates a five-layer structure, which can achieve multiple functions with tunable amplitudes with a dual-band bandpass filter and perfect absorber for sensing applications. When used as a bandpass filter, the design has two center frequencies at 0.708 and 1.733 THz with a 3-dB bandwidth of 0.312 and 0.160 THz, respectively. Among them, the maximum transmission of the first frequency band can attain $\ge 90$ %, while that of the second frequency band exceeds 70%. Using the phase transition characteristics of VO2 as the amplitude modulation principle, the amplitude modulation depth can reach 89.36% and 94.24%, respectively. As a sensor, a perfect absorption peak generated by this structure at 1.478 THz was used, with an absorption rate of up to 99%. Simulation results showed that its sensitivity, quality factor ( ${Q}{)}$ , and figure of merit (FOM) could reach 0.247 THz/RIU, 21.497, and 3.592 RIU $^{-{1}}$ , respectively. The combination of multiple functions gives our design important application values for bandpass filters, modulators, sensors, and other fields.