排序方式: 共有306条查询结果,搜索用时 15 毫秒
41.
We present a solution to the problem of reflection and transmission of a polarized paraxial light beam at an interface between two homogeneous media by using a two-form amplitude and an extension matrix to represent the vectorial angular spectrum of a three-dimensional (3D) light beam. We derive general formulas for the Imbert-Fedorov (IF) shift of the reflected and transmitted beams of a polarized paraxial light beam. The IF shift of two different types of polarized beams is calculated, and the influence of the polarization state and the polarization feature of the vectorial angular spectrum on the IF shift is discussed. 相似文献
42.
K.H. Jensen M.N. Alam B. Scherer A. Lambrecht N.A. Mortensen 《Optics Communications》2008,281(21):5335-5339
Optical gas detection in microsystems is limited by the short micron scale optical path length available. Recently, the concept of slow-light enhanced absorption has been proposed as a route to compensate for the short path length in miniaturized absorption cells. We extend the previous perturbation theory to the case of a Bragg stack infiltrated by a spectrally strongly dispersive gas with a narrow and distinct absorption peak. We show that considerable signal enhancement is possible. As an example, we consider a Bragg stack consisting of PMMA infiltrated by O2. Here, the required optical path length for visible to near-infrared detection (760 nm) can be reduced by at least a factor of 102, making a path length of 1 mm feasible. By using this technique, optical gas detection can potentially be made possible in microsystems. 相似文献
43.
Qiong-Yi He Xiao-Gang Wei Jin-Hui Wu Bing Zhang Jin-Yue Gao 《Optics Communications》2008,281(11):3137-3142
In a Doppler-broadened three-level Λ-type system driven simultaneously by a coupling laser and two equal-amplitude saturating laser fields with a frequency difference 2δ, the absorption spectrum of a weak probe laser exhibits multiple deep spectral holes through coherent hole-burning CHB with controllable numbers, widths, depths, and positions. More significant, changing δ or lasers directions, CHBs can degenerate into narrower and deeper spectral holes where the slope of the refractive index is very steep. The multiple narrow spectral holes in a single absorption profile are expected to have potential applications in high density storage, optical information processes, and slow-light. 相似文献
44.
We propose a new scheme for realizing left-handed electromagnetic properties in a coherently driven four-level system. At the presence of spontaneously generated coherence and the local field effect, both dielectric permittivity and magnetic permeability may have negative real parts of the same order in a small frequency band. Thus, one can achieve the negative refractive index and then manipulate it by modulating the coherent field or changing the atomic density. With incoherent pumping applied to have more remarkable spontaneously generated coherence, one can further obtain a wider frequency band of negative refraction and simultaneously reduce the accompanied absorption. 相似文献
45.
Lead zirconate titanate (PZT) thin films are deposited on platinized silicon substrate by sol-gel process. The crystal structure and surface morphology of PZT thin films are characterized by X-ray diffraction and atomic force microscopy. Depth-sensing nanoindentation system is used to measure mechanical characteristics of PZT thin films. X-ray diffraction analyses confirm the single-phase perovskite structures of all PZT thin films. Nanoindentation measurements reveal that the indentation modulus and hardness of PZT thin films are related with the grain size and crystalline orientation. The increases of the indentation modulus and hardness with grain size are observed, indicating the reverse Hall-Petch effect. Furthermore, the indentation modulus of (1 1 1)-oriented PZT thin film is higher than those of (1 0 0)- and random-oriented films. The consistency between experimental data and numerical results of the effective indentation moduli for fiber-textured PZT thin films using Voigt-Reuss-Hill model is obtained. 相似文献
46.
Xin-Mei Li 《Applied Surface Science》2008,254(20):6350-6357
Porous nanocrystalline Ti(C0.7N0.3) film on Ti6Al4V substrate was prepared by plasma electrolytic carbonitriding (PECN). The film was characterized and analyzed by using a variety of analytical techniques, such as XRD, SEM, EDX, TEM, FESEM, Rockwell C indenter, scratch tester, Vickers microhardness tester and ring-on-block tribometer. The results showed that the film was about 15 μm thick and its hardness was Hv 2369 at a load of 0.2 N. The adhesion of the film was characterized by Lc and Pc value, and was found to be about 42 N and more than 800 N, respectively. The friction coefficients and wear volume loss of the PECN-treated samples sliding against a steel counterpart were much less than those of the untreated Ti6Al4V. The film possessed a good wear-resistance and antifriction under oil-lubricated condition due to its high hardness, adhesion and fracture toughness. Also, the porous surface morphology of the Ti(C0.7N0.3) film contributed to the enhanced tribological resistance by promoting the formation of lubricant film and entrapping wear debris. 相似文献
47.
The alteration of atomic absorption via quantum coherence is observed in the degenerate two-level atomic system. It is shown that when the detuning of coupling field equals to that of probe light, i.e. two-photon resonance, the reduction of atomic absorption via electromagnetically induced transparency occurs. However, when we tune the coupling field to two-photon off-resonance, the enhancement of absorption is obtained for the probe field. The influences of one-photon detuning and intensity of coupling field on absorption are also experimentally demonstrated. 相似文献
48.
Entangled Radiation through an Atomic Reservoir Controlled by Coherent Population Trapping
下载免费PDF全文
![点击此处可从《中国物理快报》网站下载免费的PDF全文](/ch/ext_images/free.gif)
We show that it is possible to generate Einstein-Podolsky-Rosen (EPR) entangled radiation using an atomic reservoir controlled by coherent population trapping. A beam of three-level atoms is initially prepared in nearcoherent population trapping (CPT) state and acts as a long-lived coherence-controlled reservoir. Four-wave mixing leads to amplification of cavity modes resonant with RabJ sidebands of the atomic dipole transitions. The cavity modes evolve Jnto an EPR state, whose degree of entanglement is controlled by the intensities and the frequencies of the driving fields. This scheme uses the long-lived CPT coherence and is robust against spontaneous emission of the atomic beam. At the same time, this scheme is implemented in a one-step procedure, not in a two-step procedure as was required in Phys. Rev. Lett. 98 (2007) 240401. 相似文献
49.
A. Harhira L. Guilbert P. Bourson H. Rinnert 《Applied physics. B, Lasers and optics》2008,92(4):555-561
Photoluminescence related to the bound polaron NbLi4+ is investigated as a function of temperature and incident light intensity in iron-doped lithium niobate crystals with various
iron concentrations. Experiments are done under constant-wave (CW) and pulsed illumination. Its found that the decay time
is always monoexponential. The radiative lifetime, the activation energy of the nonradiative lifetime and the quenching temperature
are only weakly sensitive to iron concentration. On the other hand, the magnitude of the photoluminescence signal seems strongly
correlated to the Fe2+ concentration, and the superlinear regime evidenced at low CW illumination definitely confirms that polaron excitation in
lithium niobate is a two-step process. 相似文献
50.
C. Keller J. Schmiedmayer A. Zeilinger T. Nonn S. Dürr G. Rempe 《Applied physics. B, Lasers and optics》1999,69(4):303-309
We report experiments on the diffraction of atoms from a standing light wave in the channeling regime, characterized by long
interaction time and large potential height. The observed far-field diffraction patterns depend specifically on the way in
which the potential is switched on and off. For fast switching, the evolution is non-adiabatic and many diffraction orders
are populated. For slow switching, however, the evolution is adiabatic and the number of populated diffraction orders decreases
dramatically. The experiments are performed in two different setups employing rubidium and argon atoms, respectively. In one
of the setups, we study the dependence of the diffraction pattern on the interaction time, in the other setup that on the
incidence angle.
Received: 30 November 1998 / Revised version: 5 July 1999 / Published online: 8 September 1999 相似文献