Thermal emission (thermal radiation) is the phenomenon responsible for most of the light in the universe, including light from the sun and stars, the glow of embers in a fire, and the invisible infrared light from people and vehicles that enables thermal imaging. Though detailed understanding of thermal emission dates back over a century, recent advances have encouraged the re-examination of this phenomenon and its potential applications. This project will explore ways to utilize and engineer thermal emission for applications such as passively regulating temperatures without using external power or feedback loops, coatings that camouflage objects from infrared cameras, and improved temperature measurements at a distance. The design and implementation of thermal emitters and thermal-emission measurement schemes will involve computational design, collaboration with materials scientists, micro- and nanofabrication, and table-top optical experiments. Students working on this project will thus gain experience in all parts of the engineering process, and develop analytical, experimental, and communication skills. This project will closely integrate the research, teaching, and outreach missions, with the aims of improving undergraduate and graduate education, communicating science to the public, and increasing participation in science from students at all levels. The principal investigator will incorporate timely research findings into his advanced optics and photonics courses, which will be redesigned using a hybrid model combining lectures and a flipped classroom approach. The project will aim to expand the recruitment of students from groups underrepresented in science and technology programs via targeted recruiting into summer and graduate programs. To promote science communication, the principal investigator and his group will also launch a podcast focused on topics in applied physics, technology, and the practice of science.
Conventional wisdom grounded in the century-old Planck and Stefan-Boltzmann laws holds that thermally emitted light is broadband, unpolarized, non-directional, and becomes brighter with rising temperature. Over the last fifteen years, a number of groups have shown that it is possible to engineer the spectrum, directionality, and polarization of thermal emitters, enabling applications such as thermo-photovoltaics and high-efficiency incandescent light sources. However, other engineering degrees of freedom of thermal emitters have scarcely been explored, including temperature dependence in the emissivity, temperature non-uniformity, and wavefront selectivity. This project will explore these degrees of freedom and their applications to thermoregulation, infrared privacy, and metrology. Phase-transition materials will be used to realize thermal emitters with temperature-dependent emissivity, utilizing thin-film optical design and nanoscale defect engineering to maximize the design space. One set of emitters will enable passive regulation of temperature in systems where radiative heat transfer dominates, such as components of spacecraft or high-temperature power plants. Complementary emitter designs will enable cloaking of objects from infrared cameras, masking temperature profiles. In parallel, a new thermography technique will be developed, granting the ability to measure temperature distributions underneath the surfaces of materials. Finally, thermal emitters will be demonstrated that can directly generate a variety of complex optical wavefronts, including optical vortices and radially polarized beams.
