Thermal signature control by microscopic structures

The thermal signature of an object is determined by its thermal-infrared radiation, origi nating from the electromagnetic emission of thermally-induced stochastic currents in ma terials. While Planck’s law has well-established the upper limit of the thermal radiation  spectra for macroscopic objects, microscopic structures with characteristic lengths smaller  than the thermal wavelength exhibit an extraordinary ability to manipulate thermal radia tion beyond the constraints of Planck’s Law. Achieving spectral, directional, and spatial  control of thermal signatures holds significant applications in thermal management, energy  conservation and harvesting, and information technologies. But at the same time, there  is a substantial demand for a deepened physical understanding of thermal emission at the  microscopic scale, which facilitates the design and development of microscopic structures  for thermal radiation manipulation.  

This dissertation emphasizes the importance of theoretical and numerical studies of  microscopic thermal radiation. Our investigation approached thermal radiation from both  a first-principles perspective, developing time-efficient numerical tools for precise calcula tions of microscopic thermal radiation, and applying a phenomenological theory framework  to capture key characteristics of resonating emitters. Enabled by the theories and numerical tools developed and adopted, we designed multiple microscopic devices utilizing novel  geometries and material properties. The functionalities of these designs were demonstrated  through combined simulations and experiments.