Improvement of Angle-Selective Thermal Radiation Property Based on the Formation of Directional Emissive Surfaces on Conical Cavity Walls

We propose a method to control thermal radiation directivity by combining a conical cavity structure with a polymer waveguide. The combination of a conical cavity and a polymer waveguide suppresses lateral emission losses and achieves effective directivity control of thermal radiation, which cannot be realized by either element alone. The directivity and spectral property of thermal radiation was analyzed using ray tracing and RCWA, and verified experimentally with infrared imaging, showing improved directivity. Furthermore, arrayed conical cavities indicates potential for unique radiative surfaces. This study provides a design guideline for enhancing radiation-based energy systems such as thermophotovoltaic (TPV) devices.