yobo体育app:Scattering from singular surfaces, from AFM tip for NSOM to polygonal plates for Terahertz sensor

题目:Scattering from singular surfaces, from AFM tip for NSOM to polygonal plates for Terahertz sensor

报告人:S. T. Chui,Professor, Department of Physics and Astronomy, University of Delaware, DE 19716, USA (E-mail: chui@bartol.udel.edu



报告联系人: 孙树林



We study the response of a conical metallic surface to an external electromagnetic (EM) field by representing the fields in basis functions containing integrable singularities at the tip obtained by conformal mapping between the cone and a round disk. We found the field-induced charge distribution to consist of localized terms at the tip apex and the base and an extended bulk term along the body of the cone far way from the tip. We apply our calculation to the scattering-based scanning near-field optical microscope (s-SNOM) and successfully quantify the elastic light scattering from a vibrating metallic tip over a uniform sample. In recent s-SNOM experiments at the optical range (< 1um) the fundamental is much larger than the higher harmonics whereas at THz range (> 1mm) the fundamental becomes comparable to the higher harmonics. We find that the tip charge dominates the contribution to the higher harmonics and becomes much bigger for the THz experiments, thus providing an explanation. Our calculation is orders of magnitude faster than current approaches. We demonstrate this by extracting a two dimensional dielectric constant map from the s-SNOM image of a finite metallic disk which suggests the possibility of mapping the charge density distribution of a finite metallic surface induced by an EM field.



Siu-Tat Chui was born in Hong Kong, China on April 20, 1949. He went to McGill University in 1967 and obtained his B.S. degree in physics in 1969. He won the first prize of the 1969 University Prize Exam sponsored by the Canadian Association of Physicists while in Canada. After that, he went to Princeton University on an Imperial Oil Fellowship and obtained a Ph.D. in physics in 1972. He remained an instructor at Princeton from 1972-73. He was a member of the Technical Staff at Bell Laboratories from 1973 to 1975, an Assistant Professor at SUNY-Albany from 1975 to 1979 and joined the Bartol Research Foundation in 1979 and is currently professor. He has been visiting professors at the University of Maryland, the Institute of Materials Research of Tohoku University, Japan; the Hong Kong University of Science and Technology, Umea University, Sweden, and the Institute of Theoretical Physics, Beijing, China. He, has published more than 200 journal papers, including Physics Review Letters, Physical Review B, etc.