The study of metamaterials has emerged as a new frontier in optics and photonics, along with plasmonics. While theory has predicted unusual transmission, reflection, and emission with negative index materials, little has been done on the design and fabrication of metamaterials for tailoring thermal radiative properties. A new type of metamaterial is proposed that consists of a layer of periodic grating coupled with an opaque metallic film via a dielectric spacer. By realizing diamagnetic response and by coupling a negative permeability material with a negative permittivity material, this structure can tailor the emission and absorption properties. Rigorous modeling as well as an effective medium theory will be developed to study the interaction of thermal radiation with the fabricated nanostructures. Infrared spectrometry and emissometry will be employed to verify the theoretical predictions. Intellectual Merit: This transformative research will result in novel material structures and a better understanding of the electromagnetic wave interaction with complex materials. Moreover, this project will provide an unprecedented way of designing radiation emitters for thermophotovoltaic systems and absorbers for infrared radiation detectors. Broader Impacts: Students involved in this multidisciplinary project will gain fundamental knowledge of electromagnetic wave and thermal radiation, as well as experience in micro/nanofabrication and spectroscopic experiments. By encouraging underrepresented students to participate in research, this project will increase the opportunity for women and minorities in engineering. Undergraduate curriculum will be enhanced by the proposed Nanoscale Energy Transport course. The PI will organize conferences and give seminars to serve the community as well as to educate the public about nanoscale thermal engineering.
This project was extended for one year to a total of four years from August 2008 to July 2012. The PI and his students have given nearly 20 conference presentations, published 20 journal papers, and two book chapters, which reflect major advances across the disciplines of thermal radiation, nanoengineering, and photonics. A number of graduate students and undergraduate students have participated in this research, and have learned nanoscale heat transfer and gained hands-on experience in measuring radiative properties through coursework and lab experience. Through partial support of this project, two Ph.D. students (including one female) and two M.S. students have graduated. The students participated in this project also have had opportunities to present papers at national and international conferences and have received a number of distinctions, including (1) The Innovation Award at the First ASME Society-Wide Micro/Nano Technology Forum during IMECE2009 in Orlando; (2) the 2010 Hartnett-Irvine Award from the International Centre of Heat and Mass Transfer (ICHHM); and (3) an Outstanding Master’s Thesis Award from Georgia Tech Chapter Sigma Xi. It has been shown that magnetic (plasmon) polaritons (MPs) are responsible for the resonant absorption and transmission in metallic deep gratings as well as in double-layer nanoslit arrays. The mechanism of MPs can provide convincing explanations of enhanced transmission and absorption over a large range of geometric parameters and frequency than some previously postulated mechanisms like cavity resonance or coupled surface plasmon polaritons. Furthermore, there exist phonon-mediated MPs inside dielectric grating structures made of SiC or other polar materials. A high-temperature emissivity measurements facility was developed and used to demonstrate MP-assisted coherent thermal emission in periodic structures. The resonance phenomenon associated with MPs has promising applications in the infrared spectral region and can enhance thermophotovoltaic emitters. The PI updated ME6301 Conduction Heat Transfer in Spring 2010 and Spring 2012 by introducing the microscopic underlying physics of nanoscale heat transport. This course has stimulated interest in a large number of students both on-campus and through distance learning in the advancements of nanotechnology, and provided them a clear and deep understanding of the physical mechanisms underlying thermal transport processes. The research results were used to teach ME6309 Nanoscale Heat Transfer (Spring 2009 and Spring 2011). Furthermore, the PI initiated an undergraduate elective ME4803 Micro/Nanoscale Energy Transport in Spring 2011 that encourages and prepares undergraduates to pursue research in the related field. The PI has been invited to give lectures, seminars, and keynote speeches at a number of conferences, workshops, and universities. In particular, the PI has delivered a series of graduate seminars and lectures at major universities in China, Korea, and Finland on nanoscale thermophysical engineering. The PI also played leadership role in organizing a number of international conferences and workshops in the area of micro/nanoscale heat transfer and energy conversion. These activities have promoted interactions and collaborations as well as helped identifying the challenges and future research needs.
