Physics Department, UC Berkeley and Materials Research Division, LBNL
Nonlinear optical properties of materials are important as tools in basic research and optical technology. Recently there has been a tremendous upsurge of interest in optical nonlinear effects, especially in crystals with curved bandstructure geometry. Such materials are candidates for applications based on the conversion of light to dc current. In this talk I describe our discovery that a family of Weyl semimetals has by far the largest second-order susceptibility of any previously known crystal. In puzzling over this result, we uncovered a surprising theorem relating the strength of optical nonlinearity to a quantum invariant property of the bandstructure that unites nonlinear optics with the celebrated “modern theory of polarization.” This quantum invariant provides a new strategy for algorithmic computational searches for nonlinear materials with optimal response functions.
About the speaker
Joseph W. Orenstein earned his Ph.D. in Solid State Physics from the Massachusetts Institute of Technology in 1980. He received an IBM Postdoctoral Fellowship 1978-79, and was a Member of the Technical Staff at the AT&T Bell Laboratories from 1981 to 1989. In 1989, he was made a Distinguished Member of the Technical Staff. He joined the Physics Dept. at UC Berkeley in 1990. He is a Fellow of the American Physical Society.
Joe Orenstein's research group we use light (or electromagnetic radiation to we physicists) to probe condensed matter systems. They measure quantities like transmission and reflection coefficients, and nonlinear optical properties as well. For different experiments, the gourp uses light waves whose wavelength varies from the millimeter range to less than 0.5 micron. Currently, they are studying high-Tc superconductors organic molecular crystals.
More details on Joe Orenstein's research can be found here.