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D H Feng

Publications and source records attributed to D H Feng.

4 recordsLinked to original sources
PubMed2006

Electron spin dynamics in a self-assembled semiconductor quantum dot: the limit of low magnetic fields.

Using the trion as an optical probe, we uncover novel electron spin dynamics in CdSe/ZnSe Stranski-Krastanov quantum dots. The longitudinal spin lifetime obeys an inverse power law associated with recharging processes in the dot ensemble. No hint at spin-orbit mediated spin relaxation is found. At very weak magnetic fields (< 50 mT), electron spin dynamics related to the hyperfine interaction with the lattice nuclei is uncovered. A strong Knight field gives rise to nuclear ordering and formation of dynamical polarization on a 100-micros time scale under continuous electron spin pumping. The associated spin transients are temperature robust and can be observed up to 100 K.

Journal Article↗
PubMed2005

Incoherent subharmonic light scattering in isotropic media.

Incoherent subharmonic light scattering in isotropic media is a new kind of nonlinear light scattering, which involves single input photon and multiple output photons of equal frequency. We investigate theoretically the dependence of the subharmonic scattering intensity on the hyperpolarizability of molecules and the incident intensity using nonlinear optics theory similar to that used for Hyper-Rayleigh scattering and degenerate optical parametric oscillators. It is derived that the subharmonic scattering intensities grow exponentially or superexponentially with the hyperpolarizability of molecules and the incident intensity.

Light↗
PubMed1996

Virtual bronchoscopy: segmentation method for real-time display.

Computed tomography (CT) data sets obtained in 14 patients were used in a segmentation method for virtual bronchoscopy (VB). The method constrained the distance of propagation of a region-growing algorithm. The resulting three-dimensional bronchial model was a faithful representation of the source CT data and could be manipulated in real time at frame rates of one to two frames per second. Preliminary data showed that 90% of bronchi (up to third order) measureable on multiplanar CT reformations were also measurable at VB. The bronchial diameters measured at VB were within 1 mm of those measured on multi-planar reconstructions of the CT data.

Adult↗