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Phase decoherence of semiconductor excitons: using nonlinear optics to probe an ensemble of oscillators
Amy Spivey
University of Puget Sound This talk will focus on experiments using
three-beam transient four-wave mixing (TFWM) of sub-picosecond laser pulses to
probe the dephasing of light-hole (LH) and heavy-hole (HH) excitons and of the
non-radiative LH-HH exciton Raman coherence in weakly disordered GaAs quantum
wells. By varying the two inter-pulse
delays independently, we are able to probe the radiative inter-band and
non-radiative intra-band coherences independently. A theoretical model based on the density
matrix and including inhomogeneous broadening and inhomogeneous dephasing rates
is fit to the TFWM data to extract the dephasing rates. I will present result that relate the
dephasing rates of the LH and HH exciton coherences to the LH-HH exciton Raman
coherence as well as give insight into the role of inhomogeneous broadening in
the exciton dephasing process. |