Thermally Switchable Terahertz Absorber Based on a Vo2-Included One-Dimensional Photonic Crystal

Abstract

Here, a thermally switching absorber based on a one-dimensional photonic crystal containing a phase change material is proposed, which operates in the terahertz range. Vanadium dioxide (VO2) is utilized as the phase-change material in the structure, which shows semiconductor-to-metal transition with varying temperatures. The frequency of switching is regulated in such a way that according to the VO2 thickness, the absorption band displays switching properties from low to high frequencies and vice versa, and also from narrow to broadband absorption at the same frequency when the temperature increases from 300 to 350 K. The absorptivity in both bands is obtained at over 90%. Field distribution profile and the impedance matching technique elucidate the physical mechanism of absorption peaks. At 300 K, maximum absorption is realized by localizing the intensity at the defect layer, and at 350 K, the Tamm state excitation makes it possible to achieve perfect absorption. Also, relative impedance matching of the structure at the peak frequencies with vacuum impedance explains high absorption. Finally, the effects of incidence angle and polarization of light that influence the absorption peaks are analyzed. According to the results, the proposed absorber, despite showing switching features between two bands, also can be adjusted by incident angle for both TE and TM polarizations. This work may have potential applications in designing terahertz switches, filters, and sensors.