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| 2. |
- Chen, Zhihui, et al.
(författare)
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Exciton Polariton Contribution to the Stokes Shift in Colloidal Quantum Dots
- 2011
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Ingår i: The Journal of Physical Chemistry C. - 1932-7447. ; 115:13, s. 5286-5293
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Tidskriftsartikel (refereegranskat)abstract
- We study the exciton polariton contribution to the Stokes shift in colloidal quantum dots (QDs). By detailed quantum mechanical description of light-matter interaction and temporal analysis of incident electromagnetic field across the QD using the finite-difference time-domain method, we have shown that the optical excitation of an exciton in the QD and its coupling with the excitation radiation (i.e., exciton polariton) induce strong variations in the dielectric constant of the QD which contribute significantly to the Stokes shift and cause modifications 50 in the absorption spectrum that agrees well with experiments.
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| 3. |
- Chen, Zhi-Hui, et al.
(författare)
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Comb-shaped photonic crystal structure for efficient broadband light diffraction and funnelling in solar cells
- 2012
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Ingår i: Solar Energy Materials and Solar Cells. - 0927-0248. ; 99, s. 316-320
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Tidskriftsartikel (refereegranskat)abstract
- We present a comb-shaped photonic-crystal (PhC) rods-lattice structure of broadband light diffraction and funnelling for solar cell applications. It is shown that the photonic band of this PhC structure is very dispersive over a broad bandwidth so that light will be efficiently diffracted in the wavelength region of solar radiation. The PhC structure also creates resonance modes leading to further diffraction and funnelling of light so that the light propagates in many pathways in the whole PhC lattice region, which will greatly facilitate light-matter interaction when light-absorbing elements are embedded in the PhC structure. The proposed structure is also valid for photodetection applications.
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| 4. |
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| 5. |
- Chen, Zhihui, et al.
(författare)
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Multiple beam splitting to free space from a V groove in a photonic crystal waveguide
- 2011
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Ingår i: Applied physics. B, Lasers and optics (Print). - 0946-2171. ; 102:4, s. 857-861
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Tidskriftsartikel (refereegranskat)abstract
- We present multiple-beam splitting to free space from a V groove in a two-dimensional photonic crystal waveguide (PCW) with a few additional dielectric rods at the exit of the PCW. Numerical study shows that 'one-beam-in to two-beams-out' (one-to-two, also denoted as Y-shaped), one-to-three, and one-to-five beam splittings can be easily realized over a wide bandwidth, and the split beams have remarkable properties such as symmetric energy distributions and high directional transmissions. Off-axis directional emission can also be achieved by simple displacements of the additional rods at the exit of the PCW.
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| 6. |
- Chen, Zhihui, et al.
(författare)
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Time-resolved photocurrents in quantum well/dot infrared photodetectors with different optical coupling structures
- 2012
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Ingår i: Applied Physics Letters. - 0003-6951. ; 100:4, s. 043502
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Tidskriftsartikel (refereegranskat)abstract
- Temporal developments of photocurrents excited by an infrared radiation pulse in quantum well/dot infrared photodetectors with different optical coupling structures have been theoretically studied. It is shown that the light diffraction in a conventional reflective grating structure is a near-field effect containing severe crosstalk from neighboring pixels. A concave reflector not only eliminates the crosstalk but also strongly diffracts and focuses the incident electric field into deep active layers, which significantly increases the photocurrents in the photodetectors.
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| 7. |
- Engström, Olof, 1943-, et al.
(författare)
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Electron capture cross sections of InAs/GaAs quantum dots
- 2004
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Ingår i: Applied Physics Letter. - 0003-6951. ; 85:14, s. 2908-2910
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Tidskriftsartikel (refereegranskat)abstract
- The thermal emission rates of electrons from InAs/GaAs quantum dots were measured, to found the capture cross sections in the extremely high region of 10-11-10-10 cm2. An additional method based on a static measurement at thermal equilibrium was used where the Fermi level was positioned at the free energy level of the quantum dot s shell. A Schottky diode with a plane of QDs grown in its depletion region and back-biased in such a way that the Fermi level coincides with the electron energy level. The Fermi level passes the lowest energy level of the QD, at the voltage marked by Vp in the graphs.
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| 9. |
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| 10. |
- Fu, Kai, et al.
(författare)
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Kinetic Monte Carlo study of metal organic chemical vapor deposition growth dynamics of GaN thin film at microscopic level
- 2008
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Ingår i: Journal of Applied Physics. - 0021-8979. ; 103:10, s. 103524
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Tidskriftsartikel (refereegranskat)abstract
- Group III nitrides, especially gallium nitride (GaN), have many applications. The materials are usually grown by metal organic chemical vapor deposition (MOCVD) technology. By combining the computational fluid dynamics and kinetic Monte Carlo method, we present a multiscale modeling of fluid dynamics, thermodynamics, and molecular dynamics to study the chemical and physical growth process of GaN in a standard MOCVD reactor, which shows a general agreement with experimental results. The theoretical model thus provides us with a fundamental guideline for optimizing GaN MOCVD growth at the microscopic level.
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