Braun Group People
Xindi Yu ,
Graduate Student in Materials Science and Engineering
B.S. in Physics Fudan University, Shanghai, China 2003
M.S. in Physics University of Michigan-Ann Arbor 2004
My research so far has been focused on dielectric-metallic photonic crystals: periodic structures composed of both dielectric material and metal. Some of these structures are believed to have superior optical properties over conventional dielectric photonic crystals. Also the absorptive nature of metal provides the potential for those structures to be designed as frequency selective absorption/emission devices.
Other research interests include plasmonics, novel micro/nano fabrication techniques, colloidal self-assembly
Research description:
Since the discovery of the wavelength-selective emissivity of tungsten woodpile structure, lots of effort has been paid to find 3D metallic photonic structures with similar optical effects and simpler fabrication routes. We created 3D metallic inverse opal structures with different structural openness using an electro-chemical approach. Extensive optical study revealed that before metal filling fraction is significantly reduced, all optical properties are affected only by the surface of the structure, which can be explained by a combination of Bragg surface plasmon and Mie plasmon. The penetration depth of light into the 3D structure is increased with reducing metal filling fraction and structure becoming hollower. At all metal filling fraction, absorption and emission are strongly modulated from the properties of bulk metal. However, sharp transition between high to low emissivity doesn’t appear, which limits the potential application. But the electro-chemical approach is compatible with other popular techniques in fabricating 3D periodic structures, like laser holography, phasemask lithography, direct writing. A combination of those might generate structures with stronger optical properties
Selected Publication:
Jian Zi, Xindi Yu, Yizhou Li, Xinhua Hu, Chun Xu, Xingjun Wang, Xiaohan Liu, and Rongtang Fu: Coloration strategies in peacock feathers, PNAS, vol.100 12576-12578 (2003)
Professor Paul Braun • Phone: +1.217.244.7293 • Fax: +1.217.333.2736 • Email: pbraun@illinois.edu
Department of Materials Science and Engineering • University of Illinois at Urbana-Champaign