SUMMARY

Coherent thermal emission with a specified polarization has been observed in micro/nanostructured materials supporting electromagnetic resonances. In general, the emissivity of metamaterial is spectral, angular, and polarized-dependent. This proposal aims to investigate the design and characterization of circularly polarized thermal emitters. The proposed research is divided into three tasks.
The first task is to study the polarized-dependent radiative properties of micro/nanostructured materials. Micro/nanostructured materials with nonreciprocity and/or mirror symmetry breaking can give rise to circularly polarized emission. A mid-infrared circular polarizer based on a Weyl semimetal is theoretically demonstrated. It possesses a high circular polarization efficiency in a broad wavelength region and wide operation angle. A bilayer twisted-gratings microstructure is proposed as a full-Stokes emitter. By adjusting the twist angle between the gratings, the polarization state can be continuously tuned from linear to circular, nearly covering the entire surface of Poincaré sphere.
The second task is to directly calculate the coherent thermal emission and analyze the Stokes parameters. Direct calculations of thermal emission from both reciprocal and nonreciprocal multilayered systems are performed based on fluctuational electrodynamics. Polarimetric analysis of Stokes parameters demonstrates that thermal emission from metamaterials can be circularly or linearly polarized in different directions. The result is consistent with the statements of the modified Kirchhoff’s law, justifying the appropriateness of both the direct and indirect methods.
The third task involves exploring the possibility of using partial polarimetry to obtain the Stokes parameters and Mueller matrix. It is proposed to study the symmetries of materials and measure the full Mueller matrix by identifying the simplest combinations of polarimetry measurements. The results obtained from this research will find extensive applications in remote sensing, landmine and target detection, biomedical diagnostics, and surface and materials characterization.