Abstract
Near-field photoluminescence (NPL) spectroscopy with a spatial resolution below the light diffraction limit was used to study the optical fields of whispering-gallery modes (WGMs) in GaAs and AlGaAs microdisks (radii and quality factors ) containing InAs quantum dots (QDs). WGMs with azimuthal mode numbers and radial mode numbers , together with low- Fabry-Pérot modes and other non-WGMs, have been resolved in NPL spectra in the range of . We found that spectrally resolved NPL intensity images of the WGMs reveal azimuthal maxima around the disk circumference, which correspond to the period of the field amplitude. Using finite-difference-time-domain (FDTD) calculations, we show that the amplitude imaging arises from the interference between the WGMs and a background field formed by low- modes. We show further that such interference reflects the inhomogeneity of the radiation decay of the QD ensemble in the MD. We demonstrate a direct measurement of WGM quantum numbers in microdisks by using NPL imaging, which shows good agreement with FDTD calculations.
- Received 15 April 2008
DOI:https://doi.org/10.1103/PhysRevB.77.195322
©2008 American Physical Society