סמינר מחלקתי אלקטרוניקה פיזיקאלית : Yuri Svirko

You are invited to attend a lecture

All-optical Injection and Control of Currents in Carbon Films

By:

Yuri Svirko

Professor, Department of Physics and Mathematics,

University of Eastern Finland,

Joensuu, Finland

Abstract

Strong and broadband light absorption in graphene and other ultrathin carbon materials allows one to achieve high carrier densities essential for observation of nonlinear optical phenomena and makes graphene a unique playground for studying many-body effects. Being of strong fundamental importance, these effects also open a wide range of opportunities in photonics and optoelectronics. It is possible in particular to make use of strong photon-drag effect to generate and optically manipulate ensembles of charge carriers via direct transfer of momentum from photons of incident laser beam to excited electrons in unbiased sample.

Direction and amplitude of the photon drag currents in graphene and other carbon films are determined by polarization, incidence angle and intensity of the obliquely incident laser beam. In the two-beam experiment, when sample was irradiated with two mirror-reflected beams, one can either suppress or enhance current produced by each of the beams depending on the time delay between excitation laser pulses. Since the drag current strongly depends on the polarization of the excitation beam, the net current can also be tuned by rotating the polarization plane azimuth of the first beam. The observed phenomenon is solely based on the second order nonlinear optical effect and provides full and non-contact control of the direction, amplitude as well as temporal profile of the injected ultrafast photocurrent. This opens a very interesting opportunity to generate THz pulses with predicted waveform and gives additional insight on dynamics of hot carriers in graphene and other ultrathin carbon films.

On Thursday, December 21, 2017, 15:00

Room 011, Kitot building