102 research outputs found
Many-body Correlation Effects in the Ultrafast Nonlinear Optical Response of Confined Fermi Seas
The dynamics of electrons and atoms interacting with intense and ultrashort
optical pulses presents an important problem in physics that cuts across
different materials such as semiconductors and metals. The currently available
laser pulses, as short as 5 fs, provide a time resolution shorter than the
dephasing and relaxation times in many materials. This allows for a systematic
study of many-body effects using nonlinear optical spectroscopy. In this review
article, we discuss the role of Coulomb correlations in the ultrafast dynamics
of modulation-doped quantum wells and metal nanoparticles. We focus in
particular on the manifestations of non-Markovian memory effects induced by
strong electron-hole and electron-plasmon correlations.Comment: 107 pages including 15 figures. Review article to appear in Surf.
Sci. Report
Canonical Transformation Approach to the Ultrafast Non-linear Optical Dynamics of Semiconductors
We develop a theory describing the effects of many-particle Coulomb
correlations on the coherent ultrafast nonlinear optical response of
semiconductors and metals. Our approach is based on a mapping of the nonlinear
optical response of the ``bare'' system onto the linear response of a
``dressed'' system. The latter is characterized by effective time-dependent
optical transition matrix elements, electron/hole dispersions, and interaction
potentials, which in undoped semiconductors are determined by the
single-exciton and two-exciton Green functions in the absence of optical
fields. This mapping is achieved by eliminating the optically-induced charge
fluctuations from the Hamiltonian using a Van Vleck canonical transformation.
It takes into account all many-body contributions up to a given order in the
optical fields as well as important Coulomb-induced quantum dynamics to all
orders in the optical field. Our approach allows us to distinguish between
optical nonlinearities of different origins and provides a physically-intuitive
interpretation of their manifestations in ultrafast coherent nonlinear optical
spectroscopy.Comment: 24 page
Ultrafast response of surface electromagnetic waves in an aluminum film perforated with subwavelength hole arrays
The ultrafast dynamics of surface electromagnetic waves photogenerated on
aluminum film perforated with subwavelength holes array was studied in the
visible spectral range by the technique of transient photomodulation with 100
fs time resolution. We observed a pronounced blueshift of the resonant
transmission band that reveals the important role of plasma attenuation in the
optical response of nanohole arrays. The blueshift is inconsistent with
plasmonic mechanism of extraordinary transmission and points to the crucial
role of interference in the formation of transmission bands. The transient
photomodulation spectra were successfully modeled within the Boltzmann equation
approach for the electron-phonon relaxation dynamics, involving non-equilibrium
hot electrons and quasi-equilibrium phonons.Comment: 4 pages, 3 figure
Spin dynamics in nonlinear optical spectroscopy of Fermi sea systems
We discuss the role of many-body spin correlations in nonlinear optical
response of a Fermi sea system with a deep impurity level. Due to the Hubbard
repulsion between electrons at the impurity, the optical transitions between
the impurity level and the Fermi sea states lead to an optically-induced Kondo
effect. In particular, the third-order nonlinear optical susceptibility
logarithmiclly diverges at the absorption threshold. The shape of the
pump-probe spectrum is governed by the light-induced Kondo temperature, which
can be tuned by varying the intensity and frequency of the pump optical field.
In the Kondo limit, corresponding to off-resonant pump excitation, the
nonlinear absorption spectrum exhibits a narrow peak below the linear
absorption onset.Comment: 7 pages inluding 2 figures. Invited paper for SPIE's Optoelectronics
2001 Conferenc
Mesoscopic cooperative emission from a disordered system
Journal ArticleWe study theoretically the cooperative light emission from a system of N»1 classical oscillators confined within a volume with spatial scale L much smaller than the radiation wavelength λο=2rrc/ω0. We assume that the oscillator frequencies are randomly distributed around a central frequency ωο with some characteristic width Ω«ω0. In the absence of disorder, that is, Ω=0, the cooperative emission spectrum is composed of a narrow subradiant peak superimposed on a wide superradiant band. When Ω≠o, we demonstrate that if N is large enough, the subradiant peak is not simply broadened by the disorder but rather splits into a system of random narrow peaks. We estimate the spectral width of these peaks as a function of N, L, Ω, and λο. We also estimate the amplitude of this mesoscopic structure in the emission spectrum
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