The Woodruff School

SUMMARY

Micro/nanoscale thermal radiation is of great importance in advanced energy systems, nanomanufacturing, local thermal management, and near-field imaging. This dissertation explores the use of nanostructures, metamaterials, and two-dimensional (2D) materials to control far- and near-field thermal radiation. First, a 2D grating/thin-film periodic nanostructure is theoretically studied for their ability to excite magnetic polaritons (MPs) and surface waves, including surface plasmon polaritons and Wood’s anomaly, in order to create wavelength-selective emission for thermophotovoltaic applications. Deep metallic gratings are investigated for their coherent radiative properties due to MPs. The polarization dependence of the radiative properties of periodic anisotropic surfaces is also examined. Second, a graphene-covered deep metal grating is numerically investigated where the MPs in gratings couple with graphene. A natural phononic hyperbolic 2D material, hexagonal boron nitride (hBN), is used with metal gratings to achieve strong wavelength-selective absorption by phonon-plasmon coupling. Trapezoidal gratings made of hBN is studied for its ability to support broadband perfect absorption. The directional hyperbolic phonon polaritons are inspected for its capability to create resonance absorption in resonators with different shapes. Third, the near-field heat transfer and photon tunneling between graphene, hBN films, and heterostructures assembled by them are calculated based on fluctuational electrodynamics. The dispersion of a hybrid polariton, surface plasmon-phonon polariton, is discussed and its impact on the near-field heat transfer is elaborated. This dissertation provides a better understanding of the radiative properties of various micro/nanostructured plasmonic metamaterials and 2D materials. The results may benefit a wide spectrum of applications where thermal radiation control is highly desirable, such as personal thermal management, radiative cooling, thermal imaging, solar energy harvesting, and thermophotovoltaics.

SUBJECT:	Ph.D. Dissertation Defense

BY:	Bo Zhao

TIME:	Thursday, October 20, 2016, 10:00 a.m.

PLACE:	Love Building, 109

TITLE:	Thermal Radiative Properties of Micro/Nanostructured Plasmonic Metamaterials Including Two-Dimensional Materials

COMMITTEE:	Dr. Zhuomin Zhang, Chair (ME) Dr. Peter Hesketh (ME) Dr. Satish Kumar (ME) Dr. Wenshan Cai (ECE) Dr. Andrew Peterson (ECE)

SUMMARY Micro/nanoscale thermal radiation is of great importance in advanced energy systems, nanomanufacturing, local thermal management, and near-field imaging. This dissertation explores the use of nanostructures, metamaterials, and two-dimensional (2D) materials to control far- and near-field thermal radiation. First, a 2D grating/thin-film periodic nanostructure is theoretically studied for their ability to excite magnetic polaritons (MPs) and surface waves, including surface plasmon polaritons and Wood’s anomaly, in order to create wavelength-selective emission for thermophotovoltaic applications. Deep metallic gratings are investigated for their coherent radiative properties due to MPs. The polarization dependence of the radiative properties of periodic anisotropic surfaces is also examined. Second, a graphene-covered deep metal grating is numerically investigated where the MPs in gratings couple with graphene. A natural phononic hyperbolic 2D material, hexagonal boron nitride (hBN), is used with metal gratings to achieve strong wavelength-selective absorption by phonon-plasmon coupling. Trapezoidal gratings made of hBN is studied for its ability to support broadband perfect absorption. The directional hyperbolic phonon polaritons are inspected for its capability to create resonance absorption in resonators with different shapes. Third, the near-field heat transfer and photon tunneling between graphene, hBN films, and heterostructures assembled by them are calculated based on fluctuational electrodynamics. The dispersion of a hybrid polariton, surface plasmon-phonon polariton, is discussed and its impact on the near-field heat transfer is elaborated. This dissertation provides a better understanding of the radiative properties of various micro/nanostructured plasmonic metamaterials and 2D materials. The results may benefit a wide spectrum of applications where thermal radiation control is highly desirable, such as personal thermal management, radiative cooling, thermal imaging, solar energy harvesting, and thermophotovoltaics.