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**排序方式：**共有159条查询结果，搜索用时 109 毫秒

1.

Second-order nonlinear optical materials for efficient generation and amplification of temporally-coherent and narrow-linewidth terahertz waves

**总被引：1，自引：0，他引：1**We have considered forward and backward optical parametric oscillation and amplification, and difference-frequency generation for efficiently generating and amplifying terahertz waves in several second-order nonlinear optical materials. We have used a single crystal of CdSe as an example. We have also investigated GaSe, periodically-poled LiNbO

_{3}and LiTaO_{3}, and diffusion-bonded-stacked GaAs and GaP plates. The advantage of using birefringence in CdSe and GaSe is tunability of the output terahertz frequency. Furthermore, both CdSe and GaSe can be used to achieve the backward parametric oscillation without any cavity. On the other hand, in periodically-poled LiNbO_{3}and LiTaO_{3}, one can take advantage of large diagonal elements of second-order nonlinear susceptibility tensor. In the diffusion-bonded-stacked GaAs and GaP plates, quasi-phase matching can be achieved by alternatively rotating the plates. We have shown that it is feasible to achieve forward optical parametric oscillation in the THz domain using these plates. The advantage of using coherent parametric processes is possibility of efficiently generating and amplifying temporally-coherent and narrow-linewidth terahertz waves. Compared with a noncollinear configuration, by using the parallel wave propagation configurations, the conversion efficiency can be higher because of longer effective interaction length among all the waves. 相似文献2.

Cavity-linewidth narrowing in a ring cavity that is due to the high dispersion and reduced absorption produced by electromagnetically induced transparency (EIT) in rubidium-atom vapor has been experimentally observed. The cavity linewidth with rubidium atoms under EIT conditions can be significantly narrowed. Cavity-linewidth narrowing was measured as a function of coupling beam power. 相似文献

3.

Properties of ferroelectric nanodots embedded in a polarizable medium: atomistic simulations

**总被引：1，自引：0，他引：1**An atomistic approach is used to investigate finite-temperature properties of ferroelectric nanodots that are embedded in a polarizable medium. Different phases are predicted, depending on the ferroelectric strengths of the material constituting the dot and of the system forming the medium. In particular, novel states, exhibiting a coexistence between two kinds of order parameters or possessing a peculiar order between dipole vortices of adjacent dots, are discovered. We also discuss the origins of these phases, e.g., depolarizing fields and medium-driven interactions between dots. 相似文献

4.

Understanding sub-20 nm breakdown behavior of liquid dielectrics

**总被引：1，自引：0，他引：1**Nanoscale confinement of dielectric molecules is expected to influence their breakdown mechanism in applications such as nanoprobe based machining, molecular electronics, and other related technologies. This Letter presents the first experimental study of the breakdown of nonpolar, nonthiolated liquid dielectrics in the nanometer regime and develops a field emission assisted avalanche based approach to model such behavior. The studies show that dielectric breakdown in the sub-20 nm regime is independent of the cathode materials and is dominated by the electron emission and atomic cluster migration due to the "sub-20 nm scale confinement of the liquid dielectric." 相似文献

5.

J.W. Ekin T.M. Larson A.M. Hermann Z.Z. Sheng K. Togano H. Kumakura 《Physica C: Superconductivity and its Applications》1989,160(5-6):489-496

A double step characteristic is observed at 76 K in the transport critical current as a function of magnetic field (10

^{-4}T to 10 T) in bulk sintered Y-, Bi- and Tl-based high-*T*_{c}superconducting materials. The low-field, step-like drop in the critical current density*J*_{c}commences at magnetic fields*B*between about 0.3 and 2 mT. This is followed by a plateau region of relatively constant critical current extending from about 30 to 300 mT, and then a second drop at fields between about 0.3 and 10 T. These features occur for all three superconductor materials and are interpreted respectively as a self-field/weak-link regime, a remnant percolation path regime and a flux-flow/upper-critical-field regime. The sharpness of the transition of the voltage-current (*V-I*characteristic, represented by the transition parameter*n*(i.e.,*V*∝*I*^{n}), has a similar double-step shape as a function of magnetic field directly corresponding to the features of the*J*_{c}(*B*) characteristic. 相似文献6.

Exact stationary-state solutions of the cubic (unsaturated) nonlinearity model of degenerate two-photon absorption by counterpropagating beams are found, and are used to describe power limiting and multiple optical bistability within a Fabry-Perot etalon. 相似文献

7.

I. Filikhin V.M. Suslov B. Vlahovic 《Physica E: Low-dimensional Systems and Nanostructures》2006,33(2):349-354

A 3D model of semiconductor quantum ring (QR) based on the single sub-band approach with an energy-dependent electron effective mass is considered. The non-linear energy confinement problem is numerically solved iteratively by using the finite elements method. We calculate the energy spectrum of the electron states for the InAs/GaAs QR using the geometrical parameters obtained in the fabrication of such rings by A. Lorke, et al. (Phys. Rev. Lett. 84 (2000) 2223). The calculated energies are compared with the experimental data. 相似文献

8.

Augusto Gonzalez Juan David Serna Roberto Capote Guillermo Avendao 《Physica E: Low-dimensional Systems and Nanostructures》2005,30(1-2):134-137

Properly regularized second-order degenerate perturbation theory is applied to compute the contribution of higher Landau levels to the low-energy spectrum of interacting electrons in a disk-shaped quantum dot. At “filling factor” near , this contribution proves to be larger than energy differences between states with different spin polarizations. After checking convergence of the method in small systems, we show results for a 12-electron quantum dot, a system which is hardly tractable by means of exact diagonalization techniques. 相似文献

9.

Z. Ding D. W. Bullock P. M. Thibado V. P. LaBella Kieran Mullen 《Surface Science (including Surface Science Letters)》2003,540(2-3):491-496

The GaAs(0 0 1) surface is observed to evolve from being perfectly flat to a surface half covered with one-monolayer high spontaneously formed GaAs islands. The dynamics of this process are monitored with atomic-scale resolution using scanning tunneling microscopy. Surprisingly, pit formation dominates the early stages of island formation. Insight into the nucleation process is reported. 相似文献

10.

William G. Harter 《Journal of Molecular Spectroscopy》2001,210(2):166

Symmetries and dynamics of wave nodes in space and time expose principles of quantum theory and its relativistic underpinning. Among these are key principles behind recently discovered dephasing and rephasing phenomena known as

*revivals*. A reexamination of basic Eberly revivals, Berry “quantum fractal” landscapes, and the “quantum carpets” of Schleich and co-workers reveals a simple Farey arithmetic and*C*_{n}-group revival structure in one of the earliest quantum wave models, the Bohr rotor. These principles may be useful for interpreting modern time-dependent rovibrational spectra. The nodal dynamics of the Bohr rotor is seen to have a quasi-fractal structure similar to that of earlier systems involving chaotic circle maps. The fractal structure is an overlay of discrete versions of Bohr's rotor model. Each*N*-point Bohr rotor acts like a base-*N*quantum “odometer” which performs rational fraction arithmetic. Such systems may have applications for optical information technology and quantum computing. 相似文献