共查询到20条相似文献,搜索用时 31 毫秒
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Spontaneous emission from GaAs/AlGaAs quantum dots (QDs) embedded in photonic crystals with a narrow photonic band gap is studied theoretically. The results show that the decay lifetime is very sensitive to the sizes of QDs, and both inhibited and accelerated emission can occur, which had been indicated in a previous experiment. The Weisskopf–Wigner approximation, good for atoms and molecules, may be incorrect for QDs. A damped Rabi oscillation of the excited state with the transition frequency outside the photonic band gap may appear, which is impossible for atoms and molecules. 相似文献
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Luz E. GonzálezN. Porras-Montenegro 《Physica E: Low-dimensional Systems and Nanostructures》2012,44(4):773-777
In this work using the transfer-matrix formalism we study pressure, temperature and plasma frequency effects on the band structure of a 1D semiconductor photonic crystal made of alternating layers of air and GaAs. We have found that the temperature dependence of the photonic band structure is negligible, however, its noticeable changes are due mainly to the variations of the width and the dielectric constant of the layers of GaAs, caused by the applied hydrostatic pressure. On the other hand, by using the Drude's model, we have studied the effects of the hydrostatic pressure by means of the variation of the effective mass and density of the carriers in n-doped GaAs, finding firstly that increasing the amount of n-dopants in GaAs, namely, increasing the plasma frequency, the photonic band structure is shifted to regions of higher frequencies, and secondly the appearance of two regimes of the photonic band structure: one above the plasma frequency with the presence of usual Bragg gaps, and the other, below this frequency, where there are no gaps regularly distributed, with their width diminishing with the increasing of the plasma frequency as well as with the appearance of more bands, but leaving a wide frequency range in the lowest part of the spectrum without accessible photon states. Also, we have found characteristic frequencies in which the dielectric constant equals for different applied pressures, and from which to higher or lower values the photonic band structure inverts its behavior, depending on the value of the applied hydrostatic pressure. We hope this work may be taken into account for the development of new perspectives in the design of new optical devices. 相似文献
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A standard plane-wave expansion method is used to investigate the photonic band structure of two-dimensional square and triangular lattices composed by cylindricalshell rods (GaAs rods surrounded by air shells) embedded in a semiconducting GaAs background. An analysis of the influence of geometry of the lattice basis is performed by changing inner and outer radii. The effect of dispersive dielectric responses as well as the influence of temperature and applied hydrostatic pressure to obtain efficient tunable bandgaps has also been considered. The presence of applied magnetic field is discussed as an efficient tool for tuning of the photonic band gaps in this kind of systems. The results suggest that a combination of a doped semiconductor constituent with an anisotropic geometry provides an efficient realization of photonic systems with tunable bandgaps. 相似文献
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V.P. Kandidov A.E. Dormidonov O.G. Kosareva N. Akozbek M. Scalora S.L. Chin 《Applied physics. B, Lasers and optics》2007,87(1):29-36
The geometric phase of a three-level atom interacting with single-mode in the presence of the one-dimensional photonic band
gap material is studied. We consider dipole emitters situated in the thin slab region between two semi-infinite one-dimensionally
periodic photonic crystals, a situation reminiscent of planar cavity laser structures. It shows that the Pancharatnam phase
depends crucially on the presence of the photonic band gap. This feature is attributed to the fact that in the photonic band
gap region electromagnetic modes are not allowed to propagate into the dielectric slab and hence no interaction can take place
in this region. The outcomes are illustrated with numerical simulations applied to GaAs.
PACS 03.67.-a; 32.80.Pj; 42.50.Ct; 42.65.Yj; 03.75.-b 相似文献
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《Superlattices and Microstructures》1997,22(1):109-113
Two-dimensional photonic lattices have been fabricated in GaAs by using standard electron beam lithography and reactive ion etching techniques. In order to obtain absolute photonic band gaps at near-infrared frequencies, graphite structures which consist of parallel cylindrical rods of GaAs at the vertices of regular hexagons have been studied. Typically, for quarter micron diameter rods and half micron nearest spacing, an etching depth of more than one micron was obtained. Preliminary results from optical characterization are also presented. 相似文献
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P. V. Dolganov S. O. Gordeev V. K. Dolganov 《Journal of Experimental and Theoretical Physics》2014,118(6):891-895
The reflection spectra of a cholesteric photonic crystal have been measured. The experimental spectra are described by a theoretical expression that follows from the analytical solution of the Maxwell equations. The photonic bandgap width Δν has been determined. The photonic bandgap width changes abruptly as the position of the diffraction band changes. The temperature dependence of the relative bandgap width Δν/ν0 and the order parameter for a photonic crystal are described by Landau’s theory of phase transitions. 相似文献
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Absolute band gaps can be created by lifting the degeneracy in the bands of a photonic crystal.To calculate the band structure of a complicated photoinc crystal generated by e.g.symmetry breaking ,general forms of all possible linear operations are presented in terms of matrices and procedure to combine these operations in given.Other forms of linear operations (Such as the addition,subtraction,and translation transforms)are also presented to obtain an explicit expression for the Fourier coefficient of the dielectric function in the plane-wave expansion method.With the present method,band structures for various complicated photoinc crystals(related through these linear operations)can be obtained easily and quickly.As a numerical example,a large absolute and gap for a complicated photonic crystal structure of GaAs is found in the high reglon of normalized frequency. 相似文献
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H. Ajlani A. Meftah R. Chtourou M. Oueslati H. Maaref 《Physica E: Low-dimensional Systems and Nanostructures》2006,33(2):325-330
In the recombination spectra of AlGaAs/GaAs heterostructures, a peculiar and asymmetric photoluminescence (PL) band F has previously been reported [Aloulou et al., Mater. Sci. Eng. B 96 (2002) 14] to be due to recombinations of confined electrons from the two-dimensional electron gas (2DEG) formed at AlGaAs/GaAs interface in asymmetric quantum well (AQW). Detailed experiments are reported here on GaAs/Al0.31Ga0.69As/GaAs:δSi/Al0.31Ga0.69As/GaAs samples with different spacer layer thicknesses. We show that the band F is the superposition of two PL bands F′ and F″ associated, respectively, to AQW and a symmetric quantum well (SQW). In the low excitation regime, the F′ band present a blue shift (4.4 meV) followed by important red shift (16.5 meV) when increasing optical excitation intensity. The blue shift in energy is interpreted in terms of optical control of the 2DEG density in the AQW while the red shift is due to the narrowing of the band gaps caused by the local heating of the sample and band bending modification for relatively high-optical excitation intensity. Calculation performed using self-consistent resolution of the coupled Schrödinger–Poisson equations are included to support the interpretation of the experimental data. 相似文献
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为了在可见及近红外波段得到具有良好带隙结构的三维光子晶体,利用传输矩阵法分析了MgF2、Ta2O5 以及Ta2O5/MgF2异质结构三维光子晶体的带隙性质.结果表明:Ta2O5/MgF2异质结构三维光子晶体在820~1 020 nm的近红外波段TM模式下具有不受入射光方向影响的全方位光子带隙.该结构有望用于制作近红外光波段的偏振器件. 相似文献
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《Physics letters. A》2019,383(25):3207-3213
In this paper, the plane wave expansion method is used to calculate the photonic band structure (PBS) for the transverse electric (TE) polarization in a two-dimensional hexagonal lattice composed air holes with cross-sections in the shape of equilateral triangles embedded in a GaAs background. We consider that the dielectric constant of GaAs is dependent on both hydrostatic pressure and temperature. Further, an increase can be observed in the width of the photonic band gap (PBG) while the lengths of the sides of the equilateral triangles are increased. When the pressure increases in the presence of a constant temperature, the dielectric constant of GaAs decreases; further, the PBS exhibits a more noticeable shift toward regions of higher frequencies than that observed while the temperature is increased at a given pressure. We also observed that the PBG obtained by rotating the triangular holes by an angle θ increases when compared against the results obtained for the lattice of holes without performing any rotation. In addition, the results obtained using the supercell technique denote that the position and width of the PBG remain unchanged while removing a triangular hole from the structure, denoting the presence of a defective band within the PBG. 相似文献
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《Physica E: Low-dimensional Systems and Nanostructures》2011,43(10):2765-2767
We report the growth of self-assembled InAs/GaAs quantum dots (QDs) on germanium-on-insulator-on-silicon (GeOI/Si) substrate by antimony-mediated metal organic chemical vapor deposition. The influence of various growth procedures for the GaAs buffer layer on the QD formation and optical quality was investigated. We obtained QDs with density above 1010 cm−2, and ground state emission in the 1.3 μm band at room temperature. These results demonstrate the promising suitability of germanium-on-insulator for the monolithic integration of QD-based and other GaAs-based photonic devices on silicon. 相似文献
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Investigation of various optical transitions in GaAs/Al0.3Ga0.7As double quantum ring grown by droplet epitaxy 下载免费PDF全文
Jong Su Kim 《固体物理学:研究快报》2016,10(9):696-702
This work examines the optical transitions of a GaAs double quantum ring (DQR) embedded in Al0.3Ga0.7As matrix by photoreflectance spectroscopy (PR). The GaAs DQR was grown by droplet epitaxy (DE). The optical properties of the DQR were investigated by excitation‐intensity and temperature‐dependent PR. The various optical transitions were observed in PR spectra, whereas the photoluminescence (PL) spectrum shows only the DQR and GaAs band emissions. The various optical transitions were identified for the GaAs near‐band‐edge transition, surface confined state (SCS), DQR confined state, wetting layer (WL), spin–orbital split (EGaAs + Δo), and AlGaAs band transition. PR spectroscopy can identify various optical transitions that are invisible in PL. The PR results show that the GaAs/AlGaAs DQR has complex electronic structures due to the various interfaces resulting from DE. 相似文献
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We develop an effective way to engineer a two-dimensional GaAs photonic crystal slab with its leaky eigenmodes at desired wavelengths by investigating its spectral dispersion, particularly in terms of transmission efficiency spectra at different launch angles of the light beam. Structural parameters for the photonic crystal slab with leaky eigenmode wavelengths at both 1492 nm and 1519 nm are obtained. This may lead to the enhanced luminescence from erbium-doped trinitride-template fullerenes (Er3N@C80) on the surface of the photonic crystal slabs. 相似文献
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The plane-wave expansion method is used to calculate photonic band gaps for two structures with hollow anisotropic tellurium (Te) rods. Both structures are found to have absolute band gaps at the low- and high-frequency regions. Compared with the photonic crystal with solid Te rods, the photonic crystal with hollow Te rods has a large absolute band gap at the high-frequency region: for the triangular lattice of oval hollow Te rods, there is an absolute band gap of 0.058we (we=2πc/a), and for the square lattice of square hollow Te rods, there is an absolute band gap of 0.056we. 相似文献