Infrared radiative properties of two-dimensional square optical black holes with materials of insulators and semiconductors

Optical black hole (OBH) is a special optical structure in which the dielectric function or refractive index of media becomes gradually larger from the outside to the core. Square optical black hole (SOBH) has been proven to be a special and remarkably useful optical structure with broadband omnidirectional light absorption, and a device that is easier to fabricate than circular optical black hole (COBH). The main goal of this paper is to find potential applicable materials of SOBH due to fabrication and infrared radiative properties consideration. The infrared radiative properties of an optical slab with periodic two-dimensional SOBHs with several insulators and semiconductors materials are numerically studied with the finite-difference time-domain (FDTD) method. The results show that the spectral radiative properties of the optical slab change with different number of materials and dimensions of SOBHs. When the incidence wavelength increases to 10 μm, the absorptance of the optical slab decreases as SOBH dimension decreases. This is due to the diffraction effect. The material selection and spectral radiative property requirement should be taken into account for device designs and fabrication.

► We investigate the infrared radiative properties of SOBHs with several materials. ► The infrared radiative properties of SOBHs shift with the structure dimensions. ► The spectral absorptance decreases as the number of materials decreases. ► The absorptance decreases as λ greater than Lc/2 due to diffraction effect. ► The materials and radiative property requirement related to SOBH designs.