Multipolar interband absorption in a semiconductor quantum dot.: II.: Magnetic dipole enhancement

We derive the magnetic dipole selection rules and the magnetic dipole absorption rate for a spherical semiconductor quantum dot. We find that electric dipole and magnetic dipole transitions are exclusive and therefore can be spectrally distinguished. The magnitudes of electric and magnetic absorption rates are compared for excitation with a strongly focused azimuthally polarized beam. It turns out that spatial optical resolution can be increased by detection of the ratio of magnetic and electric absorption rates. Resolution is limited only by the purity of the laser mode used for excitation. (C) 2002 Optical Society of America.