Multi-band tunable terahertz bandpass filter based on vanadium dioxide hybrid metamaterial

A multi-band terahertz (THz) bandpass filter based on vanadium dioxide (VO₂) hybrid metamaterial is experimentally demonstrated. From bottom to top of the filter, they are 650 nm-thick high resistance silicon substrate, 100 nm-thick Silicon nitride, 125 nm-thick VO₂, 500 nm-thick Silicon nitride, and 200 nm-thick aluminium pattern. When the incident THz wave polarized along with they direction, the filter has three tunable passbands whose central frequencies locate at 0.32, 0.70 and 0.94 THz, respectively. Under bias current of 0.22 mA, the transmission of the three bands can be electrically modulated and their modulation depths are 97%, 97.5% and 96%, respectively. When the THz wave polarized in x direction, there is only one tunable passband with central frequency of 0.73 THz, and the modulation depth achieves 96.5%. The tunable mechanism is due to the Joule heat induced isolator-to-metal transition (IMT) of the VO₂ film. The proposed approach provides a promising platform for THz frequency selection.