Broadband coherent perfect absorption in epsilon-near-zero bilayer planar thin film

Abstract

Interactions of electromagnetic wave with epsilon-near-zero (ENZ) bilayer planar thin films have been extracted in near-infrared. The ENZ material properties are harnessed theoretically as broadband and narrowband coherent perfect absorption (CPA). A dielectric layer is deposited with a tunable ITO layer on substrate for analysis of narrowband CPA. The broadband spectral regimes of CPA are produced at bilayer of tunable ITOs. The designs of these planar thin films are carried out by admittance matching method at the illumination of two counter input beams. The CPA condition is obtained by this method and the mode is characterized in effective medium approximation (EMA). It develops the eigenvalue expression of CPA mode that behaves like the transverse resonance phase matching status. The output irradiance expressions are established with phase controlling beams in scattering matrix method. These devices are applicable in energy conversion, optical switching, modulation and infrared sensor at the communication system.