Prof. Jacob B. Khurgin
Johns Hopkins University, USA
地点：唐仲英楼 B501
时间：2018-11-08 10:00
In this talk we shall investigate the genesis of hot carriers in metals by investigating rigorously and within the same quantum framework all four principle mechanisms responsible for their generation: interband transitions, phonon-and-defect assisted intraband processes, carrier-carrier scattering assisted transitions and Landau damping. For all of these mechanisms we evaluate generation rates as well as the energy (effective temperature) and momenta (directions of propagation) of the generated hot electrons and holes. We show that as the energy of the incoming photons increases towards the visible range the electron-electron scattering assisted absorption becomes important with dire consequences for the prospective “hot electron” devices as four carriers generated in the process of the absorption of a single photon can at best be characterized as “lukewarm” or “tepid” as their kinetic energies may be too small to overcome the potential barrier at the metal boundary. Similarly, as the photon energy shifts further towards blue the interband absorption becomes the dominant mechanism and the holes generated in the d-shell of the metal can at best be characterized as “frigid” due to their low velocity. It is the Landau damping process occurring in the metal particles that are smaller than 10nm that is the most favorable on for production of truly “hot” carriers that are actually directed towards the metal interface. We also investigate the relaxation processes causing rapid cooling of carriers. Based on our analysis we make predictions about performance characteristics of various proposed plasmonic devices.
Jacob B. Khurgin had graduated with MS in Optics from the Institute of Fine Mechanics and Optics in St Petersburg, Russia in 1979. In 1980 he had emigrated to US, and, to his own great surprise, immediately landed a job with Philips Laboratories of NV Philips in Briarcliff Manor, NY. There for 8 years he worked with a very modest degree of success on miniature solid-state lasers, II-VI semiconductor lasers, various display and lighting fixtures, X-ray imaging, and small appliances such as electric shavers and coffeemakers (for which he holds 3 patents). Simultaneously he was pursuing his graduate studies at Polytechnic Institute of NY (nowadays NYU School of Engineering) where he had received PhD in Electro-physics in Jan. 1987. In Jan. 1988 Khurgin’ s industrial career rather abruptly came to an end, and he had joined the Electrical and Computer engineering department of Johns Hopkins University, where he had settled down and is currently a Professor. His research topics over the years included an eclectic mixture of optics of semiconductor nanostructures, nonlinear optical devices, lasers, optical communications, microwave photonics, opto-mechanics, and condensed matter physics. Currently he is working in the areas of mid-infrared frequency combs, silicon RF photonics, laser refrigeration, non-reciprocal light propagation and bio-detection. His publications include 8 book chapters, one book edited, 300+ papers in refereed journals and 36 patents. Prof Khurgin had held a position of a Visiting Professor in a number of institutions of relatively high repute– Princeton, UCLA, Brown, Ecole Normale Superieure (Paris), Ecole Polytechnique (Paris), EPFL (Lausanne), ETH (Zurich) and so on. Prof. Khurgin is a Fellow of American Physical Society and Optical Society of America, and loves dogs, skiing, kayaks and bicycles.