Abstract-Time-dependent population inversion gratings in laser frequency combs

Marco Piccardo, Dmitry Kazakov, Noah A. Rubin, Paul Chevalier, Yongrui Wang, Feng Xie, Kevin Lascola, Alexey Belyanin, and Federico Capasso

https://www.osapublishing.org/optica/abstract.cfm?uri=optica-5-4-475

In standing-wave lasers, spatial hole burning induces a static grating of the population inversion, enabling multimode operation with several independent lasing modes. In the presence of a mode-locking mechanism, these modes may become correlated, giving origin to a frequency comb. Quantum cascade lasers, owing to their ultrafast gain dynamics, are ideally suited to achieve comb operation. Here we experimentally demonstrate that the modes of a quantum cascade laser frequency comb coherently beat to produce time-dependent population inversion gratings, which spatially modulate the current in the device at frequencies equal to the mode separation and its higher harmonics. This phenomenon allows the laser to serve as a phased collection of microwave local oscillators and is utilized to demonstrate quadrature amplitude modulation, a staple of modern communications. These findings may provide for a new class of integrated transmitters, potentially extending from the microwave to the low terahertz band.

 © 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Terahertz dephasing of Landau level transitions in graphene

Harald Schneider, Jacob C. König-Otto,  Alexej Pashkin, Yongrui Wang, Alexey Belyanin, Manfred Helm,  Stephan Winnerl

http://ieeexplore.ieee.org/document/8066873/

Using degenerate four-wave mixing (DFWM), we have investigated the coherent polarization between the lowest Landau levels in graphene under resonant excitation with narrowband THz pulses. A pronounced DFWM signal is observed and its dependence on THz field strength and magnetic field detuning is explored and compared with theoretical expectations.

Abstract-Magnetopolaritons in Weyl semimetals in a strong magnetic field

Zhongqu Long, Yongrui Wang, Maria Erukhimova, Mikhail Tokman, Alexey Belyanin

https://journals.aps.org/prl/accepted/db079YeeU431ec6360d15d55d3caf290cc659514f

Exotic topological and transport properties of Weyl semimetals generated a lot of excitement in the condensed matter community. Here we show that Weyl semimetals in a strong magnetic field are highly unusual optical materials. The propagation of electromagnetic waves is affected by an interplay between plasmonic response of chiral Weyl fermions and extreme anisotropy induced by a magnetic field. The resulting magneto-polaritons possess a number of peculiar properties, such as hyperbolic dispersion, photonic stop bands, coupling-induced transparency, and broadband polarization conversion. These effects can be used for optical spectroscopy of these materials including detection of the chiral anomaly, or for broadband terahertz/infrared applications.

Abstract- Strong magneto-optical effects due to surface states in three-dimensional topological insulators

Strong magneto-optical effects due to surface states in three-dimensional topological insulators Xianghan Yao, Mikhail Tokman, and Alexey Belyanin  »View Author Affiliations

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-23-2-795

Optics Express, Vol. 23, Issue 2, pp. 795-806 (2015)
http://dx.doi.org/10.1364/OE.23.000795

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We show that a thin film of a three-dimensional topological insulator such as Bi₂Se₃ or Bi₂Te₃ can exhibit strong linear and nonlinear magneto-optical effects in a transverse magnetic field. In particular, one can achieve an almost complete circular polarization of an incident terahertz or mid-infrared radiation and an efficient four-wave mixing.

© 2015 Optical Society of America

Abstract-Superradiant Decay of Cyclotron Resonance of Two-Dimensional Electron Gases

Qi Zhang, Takashi Arikawa, Eiji Kato, John L. Reno, Wei Pan, John D. Watson, Michael J. Manfra, Michael A. Zudov, Mikhail Tokman, Maria Erukhimova, Alexey Belyanin, and Junichiro Kono
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.113.047601

We report on the observation of collective radiative decay, or superradiance, of cyclotron resonance (CR) in high-mobility two-dimensional electron gases in GaAs quantum wells using time-domain terahertz magnetospectroscopy. The decay rate of coherent CR oscillations increases linearly with the electron density in a wide range, which is a hallmark of superradiant damping. Our fully quantum mechanical theory provides a universal formula for the decay rate, which reproduces our experimental data without any adjustable parameter. These results firmly establish the many-body nature of CR decoherence in this system, despite the fact that the CR frequency is immune to electron-electron interactions due to Kohn’s theorem.

DOI: http://dx.doi.org/10.1103/PhysRevLett.113.047601

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• Published 21 July 2014
• Received 5 May 2014

© 2014 American Physical Society