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With 3-pulse wave-mixing ultrafast spectroscopy we probe simultaneously the intra and inter-band coherent dynamics in GaAs/AlGaAs quantum wells in a perpendicular magnetic field. By comparing to theory, we identify the role of inter-Landau-level coherences.
A simple first-principle analytical derivation of the permanent matrix elements of the dipole moment responsible for most of the resonant nonlinearities in III-V and II-VI semiconductors is presented.
We present a microscopic interpretation of recent differential transmission measurements of electron spin coherence in GaAs quantum wells. We show that certain unexpected features in the beat signal can reveal finer characteristics of excitonic correlations.
We demonstrate a muW-level broadly tunable THz source based on parametric down-conversion in orientation-patterned GaAs pumped by femtosecond pulses from a Tm-doped fiber laser. Generated THz powers should be scalable to mW-levels with this approach.
Preliminary measurements of the electron spin relaxation rate (T1) in charged GaAs quantum dots are made using a nonlinear optical phase-modulation spectroscopy technique. T1 approaches 46 musec at zero magnetic field.
Sum frequency data are reported from the nonlinear interaction of two coherently excited resonant modes of a two-dimensional planar photonic crystal microcavity patterned in a free-standing InP slab.
We have developed a vectorial quantum model of spontaneous parametric down-conversion in one-dimensional nonlinear photonic-band-gap structures that shows that these structures represent a promising perspective source of entangled two-photon states.
We investigated many-body and radiative coupling effects on intersubband Rabi oscillations in a multiple quantum well system. Under certain conditions, radiative coupling is the dominating effect, yielding distinctively different excitation behaviors in the wells.
We show that a guided-wave approach to Fresnel phase-matching is relevant even for thick semiconductor wafers. This approach is implemented to design a bulk GaAs optical parametric oscillator and a terahertz generator by difference-frequency generation.
We report cavity-enhanced second-harmonic generation from a tightly confining non-linear optical device for optical frequency conversion, which employs a novel waveguide-embedded dichroic mirror, highly reflective at the fundamental wavelength and transmissive at the second harmonic.
An ultrabroad infrared continuum can be produced using optical parametric generation (OPG) in quasi-phasematched GaAs. Spectra over an octave wide, spanning 4.5 to 10.7 microns, measured 20 dB down from the peak, have been observed.
We present experimental evidence for the formation of nonlinear X-waves in AlGaAs waveguide arrays. These results agree with numerical simulations based on the discrete nonlinear Schrodinger equation with an appropriate temporal dispersion term.
Terahertz (THz) radiation from p-type (100) InAs was investigated using time domain spectroscopy. Azimuthal angle dependence measurements and the ambipolar mobility theory suggest the dominant THz radiation mechanism to be that of the surge current.
Room temperature carrier lifetimes of both type-I and type-II InP-based multiple quantum wells near optical transparency were measured using the pump-probe technique. Longer carrier lifetime in the type-II sample was observed.
Polaron dephasing processes are investigated using far-infrared degenerate four wave mixing. Long (~80 ps) dephasing times are measured and a clear change from phonon-mediated to Auger-mediated dephasing is observed as the dot carrier population increases.
Experimental studies of nearly degenerate time-resolved Faraday rotation (TRFR) in GaAs and InGaAs quantum wells show that many body interactions between excitons strongly modify the TRFR response from the electron spin coherence.
Ultrafast optical bistability is demonstrated at 1550 nm in an InP-based two-dimensional photonic crystal distributed resonator. A low intensity threshold of 4 kW/cm2 is observed, with a contrast of 65% between the high and low reflectivity states.
Ballistic pure spin currents generated via quantum interference in the absorption of femtosecond pulses are demonstrated to produce transverse ballistic Hall pure charge currents and vice versa via spin-dependent asymmetric scattering processes.
Intensity of second-harmonic generation from 3D photonic crystals fabricated from opal templates impregnated by gallium nitride and silicon shows pronounce enhancement for wavelength and angles of incidence corresponding to efficient nonlinear diffraction along the Lambda direction.
We demonstrate strong-coupling and exciton hybridization in an organic-inorganic microcavity containing InGaP QWs and the small molecular weight organic tetraphenylporphyrin. The hybrid excited state is found to persist up to temperatures of 100 K.
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