Browsing by Author "Fu, Y. J."

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Anomalous diamagnetic shift for negative trions in single semiconductor quantum dots
(2010-03-01)
Fu, Y. J.
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Lin, S. D.
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Tsai, M. F.
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Lin, H.
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Lin, C. H.
We report on the magnetic response of negative trions X(-) in single self-assembled InAs/GaAs quantum dots. Unlike the conventional quadratic diamagnetic shift for neutral excitons, the observed X(-) diamagnetic shifts are small and nonquadratic. In particular, we also observed a reversal in sign of the conventional diamagnetic shift. A theoretical analysis indicates that such anomalous behaviors for X(-) arise from an apparent change in the electron wave function extent after photon emission due to the strong Coulomb attraction induced by the hole in its initial state. This effect can be very pronounced in small quantum dots, where the electron wave function becomes weakly confined and extended much into the barrier region. When the electrons gradually lose confinement, the magnetic response of X(-) will transit gradually from the usual quadratic diamagnetic shift to a quartic dependence, and finally into a special paramagnetic regime with an overall negative energy shift.
Wide spectral range confocal microscope based on endlessly single-mode fiber
(2010-08-30)
Hubbard, R.
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Ovchinnikov, Yu. B.
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Hayes, J.
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Richardson, D. J.
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Fu, Y. J.
We report an endlessly single mode, fiber-optic confocal microscope, based on a large mode area photonic crystal fiber. The microscope confines a very broad spectral range of excitation and emission wavelengths to a single spatial mode in the fiber. Single-mode operation over an optical octave is feasible. At a magnification of 10 and lambda = 900 nm, its resolution was measured to be 1.0 mu m (lateral) and 2.5 mu m (axial). The microscope's use is demonstrated by imaging single photons emitted by individual InAs quantum dots in a pillar microcavity. (C) 2010 Optical Society of America