Abstract-Transient GaAs Plasmonic Metasurfaces at Terahertz Frequencies

Yuanmu Yang, N. Kamaraju, Salvatore Campione, Sheng Liu, John L. Reno, Michael B. Sinclair, Rohit P. Prasankumar, and Igal Brener

ACS Photonics, Just Accepted Manuscript

DOI: 10.1021/acsphotonics.6b00735

Publication Date (Web): December 9, 2016

Copyright © 2016 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acsphotonics.6b00735

We demonstrate the ultrafast formation of macroscopic terahertz (THz) metasurfaces through all-optical creation of spatially modulated carrier density profiles in a deep-subwavelength GaAs film. The switch-on of the transient plasmon mode, governed by the GaAs effective electron mass and electron-phonon interactions, is revealed by structured-optical pump THz probe spectroscopy, on a time scale of 500 femtoseconds. By modulating the carrier density using different pump fluences, we observe a wide tuning of the electric dipole resonance of the transient GaAs metasurface from 0.5 THz to 1.7 THz. Furthermore, we numerically demonstrate that the metasurface presented here can be generalized to more complex architecture for realizing functionalities such as perfect absorption, leading to a 30 dB modulation depth. The platform also provides a pathway to achieve ultrafast manipulation of infrared beams in the linear and potentially, nonlinear regime.

Abstract-Terahertz magneto-optical spectroscopy of two-dimensional hole and electron systems

N. Kamaraju, W. Pan, U. Ekenberg, D. M. Gvozdić, S. Boubanga-Tombet, P. C. Upadhya, J. Reno, A. J. Taylor, R. P. Prasankumar

http://arxiv-web3.library.cornell.edu/abs/1412.5058

We have used terahertz (THz) magneto-optical spectroscopy to investigate the cyclotron resonance in high mobility two-dimensional electron and hole systems. Our experiments reveal long-lived (~20 ps) coherent oscillations in the measured signal in the presence of a perpendicular magnetic field. The cyclotron frequency extracted from the oscillations varies linearly with magnetic field for a two-dimensional electron gas (2DEG), as expected. However, we find that the complex non-parabolic valence band structure in a two-dimensional hole gas (2DHG) causes the cyclotron frequency and effective mass to vary nonlinearly with the magnetic field, as verified by multiband Landau level calculations. This is the first time that THz magneto-optical spectroscopy has been used to study 2DHG, and we expect that these results will motivate further studies of these unique 2D nanosystems.