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11.
A variational calculation is presented for the ground-state properties of excitons confined in spherical core-shell quantum-dot quantum-well (QDQW) nanoparticles. The relationship between the exciton states and structure parameters of QDQW nanoparticles is investigated, in which both the heavy-hole and the light-hole exciton states are considered. The results show that the confinement energies of the electron and hole states and the exciton binding energies depend sensitively on the well width and core radius of the QDQW structure. A detailed comparison between the heavy-hole and light-hole exciton states is given. Excellent agreement is found between experimental results and our calculated 1se-1sh transition energies. 相似文献
12.
The sensitivity to temperature of the threshold current in a strained quantum-well semiconductor laser under a perpendicular magnetic field is determined quantitatively by means of a suitable merit parameter. The values taken on by this parameter are discussed in terms of changes in the temperature and in the magnetic-field strength. 相似文献
13.
Copolymers which are synthesized by oligomers or homopolymers have quasi-one-dimensional structures. A tight-binding model
was suggested to study the organic quantum-well properties of triblock copolymers xPA/nPPP/yPA and xPPP/nPA/yPPP consisting
of polyacetylene (PA) and poly( p-phenylene) (PPP). It was found that the electronic density in the lowest conductive state
(LUMO) could be tuned by the ratios of homopolymers and interfacial coupling. The spontaneous quantum tunneling effects will
occur in triblock copolymer xPA/nPPP/yPA with the increasing interfacial coupling. 相似文献
14.
V. K. Kononenko I. S. Manak S. V. Nalivko V. A. Shevtsov D. S. Shulyaev 《Journal of Applied Spectroscopy》1997,64(2):234-241
Laser diodes and amplifiers of a new type based on asymmetric quantum-well heterostructures having a set of effective layers
of different thickness are considered. In distinction to conventional laser heterostructures, for such modified quantum-well
systems the gain spectrum and the set of lasing frequencies can be varied over a wide range by choosing the widths and the
component composition of quantum wells and barrier regions. The transformation of the amplification bands for the TE and TM
modes with the excitation current was studied. Calculations were performed for the GaAs−AlxGa1−xAs system. In a model of direct transitions the subbands of heavy and light holes as well as changes in the polarization factor
with the frequency of light are considered. A number of questions associated with spectral broadening of lines and determination
of radiation localization and distribution of quasi-Fermi levels in the effective layers are discussed.
B. I. Stepanov Institute of Physics, Academy of Sciences of Belarus, 70, F. Skorina Ave., Minsk, 220072, Belarus. Belarusian
State University. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 221–227, March–April, 1997. 相似文献
15.
16.
The principal features of changing (sweeping) the "instantaneous" emission frequency of quantum-well heterolasers as functions
of the modulation frequency and depth and the constant component of the pump current when tuning the lasing frequency within
the gain band are established using numerical modeling. The active medium is described in the framework of a two-band model
with similar distributions of levels in subbands of electrons and holes assuming transitions between ground subbands with
no k-selection rule. Emission frequency sweeping occurs because of changes in both the index of refraction of the active medium
due to a variation in the concentration of non-equilibrium charge carriers and the forbidden-band gap. Emission frequency
sweeping does not occur at low frequencies of current modulation that correspond with quasi-stationary lasing regimes. The
modulation depth of the output radiation and, therefore, the emission frequency sweeping, also approach zero for the other
limiting case of relatively high current modulation frequencies. The sweeping is greatest at intermediate current modulation
frequencies. The sweeping value is approximately halved in certain instances by taking into account the change of forbidden-band
gap of the semiconductor. In general, the sweeping value is determined by the combined effect of the modulation frequency
and depth, the constant component of the pump current, and the spectral position of the laser emission frequency within the
gain band.
Presented at the VIIth International Scientific Conference "Laser physics and optical technologies," June 17–19, 2008, Minsk,
and at the VIIth International Scientific Technical Conference "Quantum electronics," October 13–16, 2008, Minsk, Belarus.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 2, pp. 194–201, March–April, 2009. 相似文献
17.
The ground-state and lowest excited-state binding energies of a hydrogenic impurity in GaAs parabolic quantum-well wires (Q WWs) subjected to external electric and magnetic fields are investigated using the finite-difference method within the quasi-one-dimensional effective potential model. We define an effective radius Pen of a cylindrical QWW, which can describe the strength of the lateral confinement. For the ground state, the position of the largest probability density of electron in x-y plane is located at a point, while for the lowest excited state, is located on a circularity whose radius is Pen. The point and circularity are pushed along the left haft of the center axis of the quantum-well wire by the electric field dire ted along the right half. When an impurity is located at the point or within the circularity, the ground-state or lowest excited-state binding energies are the largest; when the impurity is apart from the point or circularity, the ground-state or lowest excited-state binding energies start to decrease. 相似文献
18.
采用一个光谱匹配的太赫兹(THz)量子阱探测器(QWP)研究了一激射频率约为41 THz的THz量子级联激光器(QCL)在不同驱动电流下的发射谱,分析了测量得到的发射谱谱型和谱峰位置,根据测量的发射谱估算了太赫兹量子级联激光器发射功率随驱动电流变化的情况,从而得到了THz QCL激射的电流密度范围及其阈值电流密度.文中还研究了THz QWP在不同温度下对THz QCL 激光辐射的响应特性.研究结果表明,THz QWP在表征THz QCL的发射谱方面是一种很好的探测器,并有望成为未来THz通信中的接收装置.
关键词:
太赫兹量子阱探测器
太赫兹量子级联激光器
太赫兹通信
Fourier变换红外光谱 相似文献
19.
We have proposed a scheme for double-beam optical bistability in a tunnel-coupled asymmetric double quantum-well driven by two optical fields circulating inside two independently unidirectional ring cavities. In contrast to the single-cavity case where single-photon saturated absorption and self Kerr-nonlinearity are dominant, the two-photon absorption and cross phase modulation can be enhanced via tunneling induced interference and have an important influence to the formation of bistability. The bistable behavior can be controlled effectively via the system parameters such as the input and detuning of control field, the detuning of the probe field, Fano interference strength and cooperation parameter. Furthermore, the proposed scheme has the ability to manipulate the outputs of two optical cavities simultaneously. Due to the flexible design of semiconductor quantum well, our scheme is more practical than atomic system, therefore it can be utilized to achieve dual all-optical switching which has application in optical communication and computing. 相似文献
20.
An analysis of the power-current and tuning characteristics of asymmetric multiple-layer inhomogeneously pumped quantum-well
lasers with mode selection in the external resonator was performed. It is shown that the choice of the parameters of the barrier
and active layers of the laser heterostructure and optimization of the dispersion characteristics of the selective element
of the external resonator make it possible to realize continuous tuning of the lasing wavelength in a wide spectral range
at a practically constant output radiation power.
Reported at the Second International Scientific and Technical Conference on Quantum Electronics, Minsk, November 23–25, 1998.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 687–692, September–October, 1999. 相似文献