Critical Coupling and Perfect Absorption Using α‐MoO₃ Multilayers in the Mid‐Infrared

Abstract

α‐Phase molybdenum trioxide(α‐MoO3) is a biaxial van der Waals semiconductor that can naturally support anisotropic phonon polaritons with elliptic and hyperbolic in‐plane dispersion. α‐MoO3 can meet critical coupling (CC) condition for both transverse magnetic (TM) and transverse electric (TE) polarizations along the x and y directions and exhibit high absorption in the mid‐infrared region due to strong phonon polaritons. In this study, an absorber composed of few‐layer α‐MoO3 and one‐dimensional photonic crystal separated by a cavity is proposed. Perfect absorption for TE and TM polarized light is achieved at the longitudinal and transverse optical phonon frequencies, respectively. The underlying mechanism of perfect absorption is investigated by using coupled mode theory and simulating electric field and power dissipation profiles. The results prove that CC is responsible for the perfect absorption. Moreover, the influence of the thickness of α‐MoO3 layer, width of cavity between α‐MoO3 and photonic crystal, and angle of incident light on the CC and absorption performance are examined. Accordingly, the rules for realizing perfect absorption at different operation frequencies are established. Overall, this study provides useful insights on designing a perfect absorber based on α‐MoO3 for detection and sensing applications in the mid‐infrared region.

Broadband and Incident-Angle-Modulation Near-Infrared Polarizers Based on Optically Anisotropic SnSe

“…The reflectance of s and p light R s and R p of the SnSe-SiO 2 -Si multilayers can be thus calculated with the matrix elements of T [ 39 ]: …”

Ultra-Narrowband Anisotropic Perfect Absorber Based on α-MoO3 Metamaterials in the Visible Light Region

“…Zhu et al presented tunable wide-angle and ultra-broadband perfect absorbers by using BP-dielectric multilayer stacking structure and BP-dielectric-metallic hybrid architecture [40,41], respectively. However, to our knowledge, the understanding of the interaction of light with α-MoO 3 materials is still in its infancy, and few works have been reported on the electromagnetic absorbers based on α-MoO 3 [42][43][44], especially for ultra-narrowband anisotropic perfect absorption, which are of significance for some applications, such as photodetectors, spectral imaging, and sensors.…”

Triple-Band Anisotropic Perfect Absorbers Based on α-Phase MoO3 Metamaterials in Visible Frequencies

“…Recently, Deng et al presented a broadband absorber with an in-plane trapezoid α-MoO 3 patch arrays structure in an infrared regime [ 37 ]. Dong et al proposed an absorber with a single resonant peak by utilizing α-MoO 3 combined with a dielectric distributed Bragg reflector in a mid-infrared frequency [ 38 ]. However, the potential of α-MoO 3 materials in metamaterial absorbers has been underutilized.…”