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In this work, we study carrier dynamics in gated graphene using tunable-infrared (IR)–pump/terahertz (THz)-probe spectroscopy. Interband transitions are Pauli blocked in highly doped graphene when pumping at long wavelengths.
More than 60 years ago, Zener has predicted that an electron in a periodic potential subject to a static electric field will perform harmonic oscillations (socalled Bloch oscillations) in real space. We present here results which directly prove the existence of these spatial oscillations: By observing the field-induced shift of the wannier-Stark ladder, the macroscopic dipole moment associated with...
We report thermal effects on carrier dynamics in graphene revealed by terahertz spectroscopy. We attribute our observations to extreme sensitivity of carrier density and mobility to environmental changes.
We study nonlinear THz effects in photoexcited gated graphene, using optical-pump/Zwtewse-THz-probe spectroscopy. A crossover from negative to positive differential THz transmission has been observed at the lowest doping concentration when the THz field is increased. Using a simple Drude model of the graphene photoconductivity, we attributed the observed behavior to a transition from a domain in which...
Using optical-pump/THz-probe spectroscopy on gated, undoped graphene, we find that as the amplitude of the THz probe is increased, we observe a cross-over from optically-induced transmission decrease to increase.
A fully quantum mechanical formalism is developed to calculate photon pair detection probabilities in leaky coupled-resonator optical waveguide. Using our formalism we have studied the effect of loss on pair evolution as well as higher order pair generations in the system.
Terahertz field-induced transmission enhancement in monolayer epitaxial graphene is observed with increasing terahertz field. Photoexcitation leads to further transmission enhancement that is found to be less for the higher terahertz field amplitudes.
We model the dependence of terahertz third harmonic generation in undoped graphene on the frequency of the incident pulse. We find a very strong increase in the response in going from 0.5 THz to 2 THz.
We develop a density-matrix formalism in the length gauge to simulate the nonlinear response on undoped graphene at terahertz frequencies. The generation of high harmonics is controlled by the strong interplay between intraband and interband dynamics. We present the differential signal, which reveals clear evidence of the high harmonic generation.
We report nonlinear terahertz transmission through photoexcited graphene using optical-pump/terahertz-probe technique. Transient enhancement in the terahertz transmission of the graphene sample is observed when the sample is photoexcited. This transmission enhancement is found to decrease nonlinearly with the terahertz electric field.
We report temperature dependence and thermal hysteresis behavior of terahertz transmission through photoexcited graphene. We vary the temperature between room temperature and 1800°C, and use the optical-pump/terahertz-probe differential transmission technique.
We employ a density-matrix formalism in the length gauge to simulate the nonlinear terahertz response of graphene. The generation of high harmonics is dominated by the strong interplay between intraband and interband dynamics.
We demonstrate nonlinear effects induced by an intense terahertz field on the transmission response of metamaterial structures fabricated on a silicon wafer, as well as ultrafast modulation in the terahertz response of our samples.
We present a formalism to model the coupling of photons and quantum dots in coupled cavities in photonic crystal slabs using a quasimode-based master equation. We show the effects of quasimode non-orthogonality.
We present the first experimental observation of exact dynamic localization in waveguide arrays with non-square-wave curvatures. The deviated square-wave profile offers broadband control over the bandwidth of the dynamic localization.
We study the 1s–2p exciton transition in a quantum well. If the ratio of free carrier to 1s exciton density is greater than 0.15%, screening dominates exchange and phase-space filling, yielding a red shift.
We treat multiple-quantum-dot-multiple-photon dynamics in coupled-cavity photonic crystal slab systems by projecting the Hamiltonian onto a discrete basis of quasimodes. We apply this approach to spontaneous emission into two coupled cavities.
We simulate the coherent carrier dynamics of an optically-excited, updoped AlGaAs superlattice in the presence of a Terahertz pulse using an excitonic formalism that includes 1s excitonic states as well as higher in-plane excited states and allows for dephasing and population decay. We show that this system exhibits large tunable terahertz gain due to excitonic effects, even in the presence of large...
We present the first experimental observations of exact dynamic localization of an optical beam in periodically-curved strongly-coupled waveguide arrays. Spatial and spectral measurements of two and four period devices agree well with theory.
We examine the strong-coupling quantum-dot-photon dynamics at the bandedge of a realistic, lossy, coupled-cavity waveguide and show that the signatures of bandedge coupling and Rabi oscillations are transmitted down the waveguide.
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