Numerical analysis of a thermally tunable spectrally selective absorber enabled by an all-dielectric metamirror.

ABSTRACT

In this Letter, we numerically propose a temperature-tunable, ultra-narrowband one-way perfect near-infrared radiation absorber with high transmission in the longer wavelength neighboring spectral range. We obtained this functionality by using a guided-mode resonance-based grating-waveguide metamirror that is comprised of silicon, a spacer dielectric, an absorbing semiconductor, and germanium. Within the ultra-narrow bandwidth of the guided-mode resonance excited at 1.16 µm with a full width at half-maximum of 3.3 nm, we confirmed perfect absorption when light is incident from one of the two opposite directions. Excitation from the opposite direction resulted in perfect reflection. The thickness of the entire structure is limited to about one third the operating wavelength. Furthermore, due to the temperature tunability of silicon and germanium the thermo-optical sensitivity was found to be approximately 0.068 nm/K. In addition to this spectral tunability, our proposed device supports transparency windows with 80% transmission in the higher wavelength ranges. Our device is highly promising in the applications of thermo-tunable modulators and obtaining single frequency near-infrared signals from broadband sources.