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.
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