Proposal Number: CTS-0421661 Principal Investigator: James Hammonds Affiliation: CUNY City College of New York Proposal Title: SGER: The spectral dependence of thermal radiation in micron scale spaces on the optical properties of surface microstructures
Surface polaritons (SP) are coupled electromagnetic and plasmon or phonon waves at the surface of a body, and can be driven by visible light or thermal energy. In the case of thermal energy, the associated radiated energy has a broad spectral range, while SP's have a relatively short spectral range and thus could be useful for particular applications such as those using thermophotovoltaic (TVP) cells, which are typically spectrally selective. SP's however, do not carry energy away from the body surface, and without the aid of some coupling mechanism, their special spectral properties cannot be utilized. Recent experimental and theoretical results suggest that micron and submicron scale surface texturing can alter the spectral thermal radiation properties at distances beyond the microscale regime from a substrate surface, because thermally driven SP's are scattered at the textures. While it has been demonstrated theoretically and experimentally that the spectral properties of thermal radiation can be affected by SP scattering at surface gratings, quantitative analysis of how varying the optical properties of the scattering sites can affect thermal radiation is lacking. In this research, a first step to investigating shifting thermal radiation via SP scattering will be accomplished by developing preliminary methods that will be useful in understanding the spectral properties of the radiation that results from SP scattering, and how this spectrum is related to the resonance frequencies of both the substrate and the islands. To do so, approximate analytical solutions will be obtained by developing the scattered SP in the far field limit. This work would represent the first such study and, if successful, would demonstrate that even greater control of thermal emission is possible, thus allowing for greater optimization of TPV and related devices.
