High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy

Abstract

High resolution optical spectroscopy methods are demanding in terms of either technology, equipment, complexity, time or a combination of these. Here we demonstrate an optical spectroscopy method that is capable of resolving spectral features beyond that of the spin fine structure and homogeneous linewidth of single quantum dots (QDs) using a standard, easy-to-use spectrometer setup. This method incorporates both laser and photoluminescence spectroscopy, combining the advantage of laser line-width limited resolution with multi-channel photoluminescence detection. Such a scheme allows for considerable improvement of resolution over that of a common single-stage spectrometer. The method uses phonons to assist in the measurement of the photoluminescence of a single quantum dot after resonant excitation of its ground state transition. The phonon's energy difference allows one to separate and filter out the laser light exciting the quantum dot. An advantageous feature of this method is its straight forward integration into standard spectroscopy setups, which are accessible to most researchers.

Spectral broadening of optical transitions at tunneling resonances in InAs/GaAs coupled quantum dot pairs

“…In contrast, we find that the PL linewidth of the indirect exciton is 83 ± 5 µeV, while the linewidth at the upper branch of the anticrossing is 130 ± 3 µeV. In resonant measurements, resolution limited by the laser linewidth, such as described by Czarnocki et al, 19 we have been able to show that the actual transition linewidth of the direct exciton is on the order of a few µeV, consistent with the typical radiative lifetimes for InAs/GaAs QDs. 12 For the indirect exciton one would expect a much-reduced linewidth, due to the reduced overlap of the electron and hole wavefunctions.…”

“…( 18), allowing calculation of the optical transition rates and absorption and emission spectra using Eq. (19). As a final step, Gaussian convolutions are applied to the optical transition spectra in the energy and bias directions to reproduce broadening due to the spectrometer response and local charge fluctuations, respectively.…”