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