Broadband Resonant Absorption in Anisotropic α-phase MoO3 Trapezoidal Pyramids

Trapezoidal pyramids made of α-phase MoO
₃
on a metal ground can be used to achieve perfect absorption in a relatively broad spectral region is realized in this paper. Due to the different Reststrahlen (RS) bands for different crystal axes of α-MoO
₃
, we demonstrate anisotropic broadband absorption behavior by aligning two different crystal axes of α-MoO
₃
trapezoidal gratings in the x-direction. For instance, the proposed absorber achieves a wideband absorption over 90% in the wavelength region from 10.36-12.19 μm and 11.51-16.92 μm when aligning x- and y-crystal axis of α-MoO
₃
trapezoidal gratings in the x-direction, respectively. Electromagnetic simulations show that the combination of phonon resonances within RS band results in the broadband absorption, which traps the incident wave of different wavelengths in different regions of the trapezoidal grating.