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151.
L. Hilico J. M. Courty C. Fabre E. Giacobino I. Abram J. L. Oudar 《Applied physics. B, Lasers and optics》1992,55(3):202-209
We assess in this paper the advantages and drawbacks of different nonlinear (3) materials for the purpose of generating squeezed light. The respective roles of nonlinearity, losses, response time and excess noise are discussed. Two simple models of nonlinear media are considered more precisely: parametric media with linear losses and an empty cavity with moving mirrors. 相似文献
152.
We investigate the kinetics and thermal stability of a simple Cu50.3Zr49.7 binary bulk metallic glass (BMG). The long-term thermal stability of CU50.3Zr49.7 BMG is evaluated by a newly developed method from an extension of Vogel- Fulcher-Tammann analysis. The method has been proven to be valid in CU50.3Zr49.7 or even other BMGs. 相似文献
153.
S. Odendahl 《Physics letters. A》2008,372(11):1760-1769
Spin can be described in the star product formalism by extending the bosonic Moyal product in the fermionic sector. One can then establish the relation to other approaches that describe spin with fermionic variables. The fermionic star product formalism and the fermionic path integral formalism are related in analogy to their bosonic counterparts. 相似文献
154.
Polarized visible and infrared emission characteristics of Er3+ ions in vapor-transport-equilibration (VTE)-treated LiNbO3 crystals codoped with different concentrations of Zn and Er were investigated in comparison with corresponding as-grown crystals. The results show that the VTE treatment leads to substantial spectral changes of Er3+ emissions at 0.65, 0.98 and 1.5 μm regions, and the spectral changes in the 0.98 and 1.5 μm regions appear to be Zn-concentration-dependent. It is concluded in combination with X-ray powder diffraction results and optical absorption characteristics reported previously that the VTE treatment resulted in crystalline phase transformation with respect to Er3+ ions from original LiNbO3 to ErNbO4 phase in all crystals studied. The formation of the ErNbO4 phase and the Zn2+ codopants are responsible for the VTE-induced substantial spectral changes. The emission characteristics of the ErNbO4 precipitates in the Zn/Er-codoped crystals are found to be very different from those of the ErNbO4 precipitates in the only Er-doped crystal in the infrared region, and the difference is attributed to the influence of the Zn2+ codopant on the Er3+ ion environment. The mechanism of the crystalline phase transformation is qualitatively explained from the viewpoint of the declined solubility of Er3+ ion in a Li-rich LiNbO3 crystal and from the phase diagram of Li2O-Nb2O5 system. 相似文献
155.
Xinyue Du 《Optics Communications》2008,281(24):5968-5972
Using the derived formulas for the transformation of 2 × 2 cross-spectral density matrix of the stochastic electromagnetic beams propagating through ABCD optical systems and in the turbulent atmosphere, the changes in the generalized Stokes parameters of the beams propagating under these conditions can be investigated directly. Some typical numerical calculations are illustrated relating to the electromagnetic Gaussian Schell-model beams passing through free space, focal system, dual-focus system, and the turbulent atmosphere with different structure parameters. Further extensions are also pointed out. 相似文献
156.
An analytical expression for the self-coherence function of a microcavity and a partially coherent source is derived. Excellent agreement is found between the model and the experimental measurements from two resonant-cavity light-emitting diodes. The variation of coherence length as a function of numerical aperture is examined and indicates that the variable coherence properties of planar microcavities are determined by the underlying coherences of the microcavity and the source. Furthermore, coherence-length variations approaching a factor of five can be achieved by engineering the cavity finesse. 相似文献
157.
The behaviour of the temporal Talbot effect under carrier partial coherence is analysed. This effect finds application as a passive method for multiplying the repetition rate of the intensity of pulse trains in first-order dispersive media. The study is based on the representation of the average intensity of partially coherent modulated light after first order dispersion as a coherence-dependent low pass filter acting on the intensity distribution obtained with a monochromatic carrier. The resulting coherence limitations are more restrictive in Talbot devices with high indices, due to the necessity of highly coherent carriers to produce a faithful reconstruction of trains by multiple pulse-to-pulse interference. Coherence limitations for architectures composed of externally modulated cw sources are analysed. Generalizations of the theory to several spectral lines, and its relation with the Collett-Wolf theorem are also reported. 相似文献
158.
A. Marucci P. Launois R. Moret A. Pénicaud 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(1):29-34
The phase diagram of the newly synthesized mixed crystal C60-biphenyl is investigated as a function of temperature by single-crystal X-ray scattering. Diffuse scattering investigations
evidencing complex disorder and local order effects are presented. Two phase transitions leading to two different doublings
of the high temperature unit cell are observed, at 212 K and 147 K. The first transition is attributed to the ordering of
twisted biphenyls, which couples to the orientational ordering of the C60 molecules as the temperature decreases. Full ordering of the C60 molecules is achieved below 100 K only, in the low temperature phase. The rich phase diagram of C60-biphenyl is due to the interplay between fullerene and biphenyl ordering phenomena.
Received 31 August 2001 and Received in final form 4 December 2001 相似文献
159.
A new theoretical method combining analyser-based and propagation-based hard X-ray phase-contrast imaging is investigated. Unlike the previous theoretical model of the combined imaging method constructed under the assumption of slow variation of the individual transfer functions (large Fresnel numbers), a new model proposed in this paper uses the assumption of a weak scatterer (analogous to the first Born approximation). Consequently, the results are not limited to the case of short propagation distances or low-resolution imaging. An explicit expression for the combined transfer function is derived and analytical and numerical examples solving related inverse imaging problems are presented. 相似文献
160.
Polycrystalline SrTiO3 thin films were prepared by pulsed laser deposition technique. The phonon properties and structural phase transition were studied by Raman spectroscopy. The first-order Raman scattering, which is forbidden in SrTiO3 single crystal, has been observed in the films, due to the structural distortion caused by strain effect and oxygen vacancies. The Fano-type line shape of TO2 phonon reveals the existence of polar microregions in the STO thin films. The evolution of TO2 and TO3 phonons with temperature shows the occurrence of a structural phase transition at 120 K related to the formation of polar macroregions in the films. 相似文献