Ultra-broadband actively tunable terahertz modulator based on multi-stacked metamaterial

The flexible and tunable metasurfaces employing phase transition materials hold significance in developing terahertz photonic components for applications in 6G and beyond. This research article introduces ultra-broadband terahertz amplitude modulation caused by the metal-insulator phase transition in a vanadium dioxide thin film. Utilizing a multi-stacked metamaterial (MM) on a flexible substrate, the proposed design offers an ultra-broadband bandwidth. The high-quality vanadium dioxide film, capable of undergoing metal-insulator phase transition with temperature, is grown on a quartz substrate. Flexible multi-stacked MM, separately fabricated in a clean room, is transferred onto the VO₂ film. Terahertz time-domain spectroscopy reveals an ultra-broadband FWHM of 1.02 THz and a high modulation depth of 55% as the temperature of the integrated MM increases from 50 to 90 °C. A transmission line model is proposed to understand the resonance broadening observed through simulation and experiments. This work showcases a flexible and actively tunable ultra-broadband modulator developed via the facile polyimide-mediated peel-off technique of the MM and its transfer onto the phase transition material. The study unlocks avenues to develop versatile, flexible, tunable terahertz photonics components for applications in wireless communication systems.