Thermally controllable perfect absorber at telecommunication spectrum based on phase change material and cavity grating

Abstract

We proposed and demonstrated a high-efficiency active absorber based on surface plasmon polaritons and Fabry–Perot cavity operating at telecommunication regime. The absorber comprised a resonance-cavity grating sandwiched between a metal and vanadium dioxide (VO2), a phase-change material (PCM) widely used in optical devices. As a PCM, VO2 is characterized by a large difference in the refractive index between the insulator and metallic phases initiated by various stimuli, such as heat, voltage, and current, thereby enabling the tailoring of optical properties in different systems. Herein, heating caused VO2 to undergo a transition from insulator to metallic phase, resulting in changes in its optical properties. For transverse magnetic polarization at resonance wavelength, the cavities beneath the VO2 confined the impinging light when VO2 was in insulator phase. Our simulation results revealed that the confinement enhanced the absorption up to 99%; conversely, when the system was heated beyond the phase-transition temperature of VO2 (68 °C), the absorption intensity decreased from 99% to 30%. For transverse electric polarization, a similar behavior was observed but the absorption intensity was about 50% at telecommunication band. These findings indicated that the proposed absorber was active, intensity tunable and highly responsive and may have applications in sensors and imaging.