Independent Modulation of the Phase and Amplitude of Electromagnetic Waves Based on the Phase Change of VO2 and Mode Coupling

Metasurfaces in a metal–semiconductor–metal configuration have been studied in multiple contexts, including perfect absorption and phase modulation. Nevertheless, limit progress has been achieved in independent phase modulation. To study further in this work, a metasurface composed of an Au film/ VO2 film/ Au patch array with square holes was proposed in this paper. Through simulating and analysing the optical properties, simulated results indicated that an extremely switchable function can be realized by modulating the phase transition of VO2, when VO2 was in the metal (semiconductor) phase, the whole structure represented as ON (OFF) state. Additionally, the efficient modulation depth is approximately 99.6% for the y-polarization at a wavelength of 2.019 µm. What’s more, by modulating symmetry-breaking of the structure or polarization, an extreme reflection phase change can been applied. As for the former, by adjusting the asymmetry degreed, the reflection phase can change from less than 180° to nearly 360°, and for the latter, the adjustment in polarization resulted in a phase change of nearly 180° for the x-polarization and nearly 360° for the y-polarization. While the amplitude remained almost constant at the corresponding wavelength. That is to say, an independent regulation of amplitude and phase was accomplished. And a two-mode one-port temporal coupled mode theory supported by full-wave simulations can explain the underlying physics of the designed independent phase modulation. The research findings mentioned above established the possibility for plasmonic integration as well as the design of multi-functional devices such as gradient metasurfaces and temperature-controlled switches.