An Amplitude Tunable Dual-Band Bandpass Filter With Perfect Absorption and Its Sensing Applications
Aijun Zhu, Zongteng Li, L. J. Cheng, Cong Hu, Rabi Mahapatra
Abstract
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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\ge 90$ </tex-math></inline-formula> %, 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 ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}{)}$ </tex-math></inline-formula> , and figure of merit (FOM) could reach 0.247 THz/RIU, 21.497, and 3.592 RIU <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula> , respectively. The combination of multiple functions gives our design important application values for bandpass filters, modulators, sensors, and other fields.