634 research outputs found
Nonlinear dynamics in superlattices driven by high frequency ac-fields
We investigate the dynamical processes taking place in nanodevices driven by
high-frequency electromagnetic fields. We want to elucidate the role of
different mechanisms that could lead to loss of quantum coherence. Our results
show how the dephasing effects of disorder that destroy after some periods
coherent oscillations, such as Rabi oscillations, can be overestimated if we do
not consider the electron-electron interactions that can reduce dramatically
the decoherence effects of the structural imperfections. Experimental
conditions for the observation of the predicted effects are discussed.Comment: REVTEX (8 pages) and 4 figures (Postscript
Polarization dependence of the two-photon Franz-Keldysh effect
The effect of a constant electric field on two-photon absorption in a direct
band gap semiconductor is calculated using an independent-particle theory. Two
band structure models for GaAs are used: a two-band parabolic model and an
eight-band "k dot p" model. Both predict a strong dependence of the two-photon
electroabsorption spectrum on the polarization of the light with respect to the
constant field. We attribute the polarization dependence to the strong effect
of a constant field on intraband dynamics.Comment: 5 pages, 1 figur
Frequency Comb Assisted Diode Laser Spectroscopy for Measurement of Microcavity Dispersion
While being invented for precision measurement of single atomic transitions,
frequency combs have also become a versatile tool for broadband spectroscopy in
the last years. In this paper we present a novel and simple approach for
broadband spectroscopy, combining the accuracy of an optical fiber-laser-based
frequency comb with the ease-of-use of a tunable external cavity diode laser.
This scheme enables broadband and fast spectroscopy of microresonator modes and
allows for precise measurements of their dispersion, which is an important
precondition for broadband optical frequency comb generation that has recently
been demonstrated in these devices. Moreover, we find excellent agreement of
measured microresonator dispersion with predicted values from finite element
simulations and we show that tailoring microresonator dispersion can be
achieved by adjusting their geometrical properties
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