10 research outputs found
Highly tunable hybrid metamaterials employing split-ring resonators strongly coupled to graphene surface plasmons
Metamaterials and plasmonics are powerful tools for unconventional
manipulation and harnessing of light. Metamaterials can be engineered to
possess intriguing properties lacking in natural materials, such as negative
refractive index. Plasmonics offers capabilities to confine light in
subwavelength dimensions and to enhance light-matter interactions.
Recently,graphene-based plasmonics has revealed emerging technological
potential as it features large tunability, higher field-confinement and lower
loss compared to metal-based plasmonics. Here,we introduce hybrid structures
comprising graphene plasmonic resonators efficiently coupled to conventional
split-ring resonators, thus demonstrating a type of highly tunable
metamaterial, where the interaction between the two resonances reaches the
strong-coupling regime. Such hybrid metamaterials are employed as high-speed
THz modulators, exhibiting over 60% transmission modulation and operating speed
in excess of 40 MHz. This device concept also provides a platform for exploring
cavity-enhanced light-matter interactions and optical processes in graphene
plasmonic structures for applications including sensing, photo-detection and
nonlinear frequency generation
Quantum-dot lithium in the strong-interaction regime: Depolarization of electron spins by a magnetic field
Magnetic field usually leads to a polarization of electron spins. It is shown
that in a system of {\em strongly interacting} particles applying magnetic
field may lead to an opposite effect -- depolarization of electron spins.
Results of the work are based on an exact-diagonalization study of quantum-dot
lithium -- a system of three Coulomb interacting two-dimensional electrons in a
parabolic confinement potential.Comment: 4 pages, incl 3 figure
Comment on "Photon-assisted electron transport through a quantum point contact in a microwave field" (Pis'ma v ZhETF 102(6), 417 (2015))
Terahertz wave amplification, stimulated by dc electric current, in grating coupled low-dimensional electron systems
Giant enhancement of the third harmonic in graphene integrated in a layered structure
Graphene was shown to have strongly nonlinear electrodynamic properties. In
particular, being irradiated by an electromagnetic wave with the frequency
, it can efficiently generate higher frequency harmonics. Here we
predict that in a specially designed structure "graphene -- dielectric --
metal" the third-harmonic () intensity can be increased by more than
two orders of magnitude as compared to an isolated graphene layer.Comment: 4 pages, 3 figure
Microwave response of a two-dimensional electron stripe: electrodynamic effects and the influence of contacts
Gate-tunable nonlinear refraction and absorption in graphene-covered silicon nitride waveguides
The nonlinear optical properties of graphene have received significant interest in the past years. Especially third-order nonlinear effects have been demonstrated to be large. Recently several groups have shown, through four-wave mixing (FWM) and third harmonic generation (THG) experiments, that the optical nonlinearity of graphene can be tuned through electrostatic gating. These effects are quantified by a strongly tunable vertical bar sigma((3))(s)vertical bar, with sigma((3))(s) the complex third-order conductivity. Here, by simultaneously observing cross-phase and cross-amplitude modulation on a silicon nitride waveguide covered with gated graphene, we are able to confirm such strong tunability for these nonlinear effects as well. Moreover, we can separately quantify the real and imaginary parts of sigma((3))(s), which respectively represent nonlinear absorption and refraction. This unveils a tunability that is far more drastic than what could be observed through FWM or THG, including sign changes in both the nonlinear absorption and refraction. Our results are confirmed by a theoretical model for the optical nonlinearity of graphene. The ability to tailor the nonlinearity of graphene to this extent can lead to new opportunities, such as nanophotonic devices with electrically tunable nonlinear properties