Rapid technological progress continues to provide new ways of manipulating and confining light on the nanoscale. The talk will discuss how 2D materials (such as graphene) create novel states of light that facilitate new effects of light-matter interaction and give new insight into old and fundamental problems in physics.        We develop a new electron-plasmon scattering theory to propose a highly directional, tunable and monochromatic radiation source based on free electrons interacting with graphene plasmons. Graphene plasmons show strong confinement of light, 200-300 times more than light of the same frequency in vacuum. This enables the generation of high frequency radiation from relatively low energy electrons, bypassing the need for lengthy acceleration of the electrons. For instance, highly-directional 20 keV photons could be generated in a table-top design using electrons from conventional radiofrequency (RF) electron guns.

A related property of plasmons is their potentially very slow phase velocity, which for plasmons in 2D conductors can be several hundred times slower than the speed of light. We show how this property creates the scenario where the velocity of light can become comparable for the first time to that of charge carriers flowing through graphene. Then, the interaction between the charge carriers and the plasmons presents a highly efficient, tunable, and ultrafast conversion mechanism from electrical signal to plasmonic excitation. This happens since the velocity of the charge carriers breaks the “light barrier”, leading to Čerenkov radiation of plasmons in 2D. Quantum mechanical considerations in the graphene Čerenkov effect reveal new features that the usual classical treatment does not predict.

Altogether, the seminar will touch topics in light matter interaction, condensed matter physics, photonics, as well as in electron beam and accelerator physics.

[1] L. J. Wong*, I. Kaminer*, O. Ilic, J. D. Joannopoulos, and M. Soljačić, Toward Graphene Plasmon-Based Free-Electron IR to X-ray Sources,Nature Photonics 10, 46 (2016)

[2] I. Kaminer, M. Mutzafi, A. Levy, G. Harari, H. Herzig Sheinfux, S. Skirlo, J. Nemirovsky, J. D. Joannopoulos, M. Segev, M. Soljačić, Quantum Cerenkov Radiation: Spectral Cutoffs and the Role of Spin and Orbital Angular Momentum,PRX 6, 011006 (2016).

[3] I. Kaminer, Y. Tenenbaum Katan, H. Buljan, Y. Shen, O. Ilic, J. J. Lopez, L. J. Wong, J. D. Joannopoulos, M. Soljačić, Quantum Čerenkov Effect from Hot Carriers in Graphene: An Efficient Plasmonic Source, Nature Communications, 7, 11880(2016).

[4] N. Rivera*, I. Kaminer*, B. Zhen, J. D. Joannopoulos, and M. Soljačić,Shrinking Light to Allow Forbidden Transitions on the Atomic Scale, arXiv:1512.04598 (2016).

Ido is a graduate of the Technion Excellence Program, receiving his Bachelor in both Electrical Engineering and Physics. He was granted the Knesset (Israeli Parliament) Award for outstanding undergraduate student achievements in 2007. Ido has completed his PhD degree in Physics, where he discovered new classes of accelerating beams in nonlinear optics and electromagnetism, for which he received the 2012 Israel Physical Society Prize, and the 2014 APS Award for Outstanding Doctoral Dissertation in Laser Science. Ido is currently a Marie Curie fellow at MIT working with Prof. Marin Soljačić and Prof. John Joannopoulos. At MIT, Ido is studying new kinds of light-matter interactions in 2D materials, and new ways to generate light from terahertz to x-ray.

时间：2016年6月29日（星期三）上午10：30

地点：中科院物理研究所M236会议室

联系人：金奎娟研究员（Tel：82648099）

邀请人：陆凌副研究员（Tel：82649203）

主办单位：中国科学院光物理重点实验室