Ultra-flat and Ultra-small: New Approaches to Atomic-Resolution Nanofabrication with Applications to Sensing and Spectroscopy
Department of Electrical and Computer Engineering
University of Minnesota, Minneapolis, USA
Unlike conventional diffractive optical devices, realization of high-performance optical nanostructures based on metals presents daunting challenges for both fabrication and modeling. Extreme squeezing of optical energy in metallic nanostructures, such as gaps and tips, is possible via surface plasmon waves, yet they are highly susceptible to defects and nanometric surface roughness. This presentation will focus on two nanofabrication techniques that our team has developed to overcome these challenges, namely, template stripping for making ultra-smooth patterned metals and atomic layer lithography for wafer-scale production of sub-nanometer-wide gaps. Applications of ultra-flat and ultra-small optical structures produced via these methods will be presented, including sensing, super-resolution optical microscopy, and visible/IR/THz spectroscopy.
From a computational modeling perspective, these extremely scaled structures (e.g. 1-nm-wide metallic slits) push the limits of existing modeling techniques because of the enormous mismatch in critical lengths scales. For example, the wavelength of incident THz beams can be up to six orders of magnitude larger than the 1-nm-wide slit, yet experimentalists can now produce such structures and measure their optical properties routinely. Examples of such challenging multi-scale computational problems will be discussed.
Biography: Sang-Hyun Oh obtained his B.S. in Physics from KAIST and Ph.D. in Applied Physics from Stanford University, in 1996 and 2001, respectively. After postdoctoral research at Bell Laboratories and the University of California at Santa Barbara, he joined the ECE department at the University of Minnesota, Twin Cities in 2006. He is currently an Associate Professor of ECE and runs a lab focused on plasmonics, nanofabrication, and biosensing. He is a recipient of the young faculty awards from DARPA, ONR, NSF CAREER, ACS PRF, and 3M.