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1.
In this paper, based on the extended Huygens–Fresnel integral formula, the analytical expression for the beam coherence-polarization (BCP) matrix of the partially coherent azimuthally polarized (PCAP) beams propagating in turbulent atmosphere has been derived. The distribution of the spectral density, the spectral degree of polarization, the spectral degree of coherence and the spectral degree of cross-polarization of the PCAP beams propagating in turbulent atmosphere with different coherences in the source are investigated in detail. It is shown by numerical results and analysis that the distribution of the spectral properties of the PCAP beam will change on propagation in a turbulent atmosphere, and this change is dependent upon the degree of coherence of the source beam and atmospheric turbulence. It is also shown that even through the source beam is chosen as δgxx ≠ δgyy the distribution of the spectral density, the spectral degree of polarization, the spectral degree of coherence and the spectral degree of cross-polarization in the far field tends to symmetrical profile. 相似文献
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3.
Guoquan Zhou 《Optics & Laser Technology》2009,41(8):953-955
Based on the second-order moments, the beam propagation factors and the kurtosis parameters of a Lorentz beam have been investigated. The M2 value of a Lorentz beam is verified to be . The analytical expressions of the kurtosis parameters have been derived. The kurtosis parameter varies upon the propagation, and it is decided by two ratios z/zrx and z/zry. The kurtosis parameter versus the two ratios z/zrx and z/zry is plotted and discussed in detail. This work is of benefit to the practical application of laser sources that produce highly divergent beams. 相似文献
4.
C. L. Ding L. Z. Pan B. Lü 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,59(2):329-336
Taking the stochastic electromagnetic J
0-correlated Schell-model pulsed
(JSMP) beam as a typical example of stochastic spatially and spectrally
partially coherent electromagnetic pulsed beams, the analytical expressions
for the cross-spectral density matrix, spectral density, spectral degree of
polarization and spectral degree of coherence of stochastic electromagnetic
JSMP beams propagating in free space are derived, and used to study the
changes in the spectrum, polarization, and coherence of stochastic spatially
and spectrally partially coherent electromagnetic JSMP beams. It is shown
that the on-axis spectrum is blue-shifted in free-space propagation and is
dependent on the pulse temporal coherence length and spatial correlation
parameter. The distribution of the on-axis spectral degree of polarization
depends on the frequency and spatial correlation parameter. The spectral
degree of coherence increases with increasing pulse temporal coherence
length. The results derived are interpreted physically. 相似文献
5.
Based on the theory of coherence, an analytical propagation formula for partially polarized and partially coherent hollow Gaussian Schell-model beams (HGSMBs) passing through a paraxial optical system is derived. Furthermore, we show that the degree of polarization of source may affect the evolution of HGSMBs and a tunable dark region may exist. For two special cases of fully coherent and partially coherent δxx = δyy, normalized intensity distributions are independent of the polarization of source. 相似文献
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Ce:KNSBN晶体衍射特性研究 总被引:1,自引:0,他引:1
在非同时读出条件下测量了Ce:KNSNB晶体两波耦合体光栅衍射效率随写入光强比、写入光偏振态和写入光夹角的变化关系,并与同时读出条件下衍射效率变化规律的测量结果进行了比较,发现二者基本一致.利用耦合波理论对实验结果进行了理论分析和拟合,拟合结果和实验数据较好的吻合. 相似文献
8.
Optimization of the design for beamline with fast polarization switching elliptically polarized undulators
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Jiefeng Cao Yong Wang Ying Zou Xiangzhi Zhang Yanqing Wu Renzhong Tai 《Journal of synchrotron radiation》2016,23(2):436-442
Fast switching of X‐ray polarization with a lock‐in amplifier is a good method for acquiring weak signals from background noise for X‐ray magnetic circular dichroism (XMCD) experiments. The usual way to obtain a beam with fast polarization switching is to use two series of elliptically polarized undulators (tandem twin EPUs). The two EPUs generate two individual beams. Each beam has a different polarization and is fast switched into the beamline. It is very important to ensure that the energy resolution, the flux and the spot size at the sample of the two beams are equal in XMCD experiments. However, it is difficult in beamline design because the distances from the two EPUs to the beamline optics are different and the beamline is not switchable. In this work, a beamline design without an entrance slit for fast polarization switching EPUs is discussed. The energy resolution of the two beams can be tuned to be equal by minor rotation of the optics in the monochromator. The flux of the two beams can be balanced through separation blades X, Y in the exit slit, and by adjusting the position of the X blades along the beam. The spot size of the two beams can be adjusted to be equal by shifting the sample as well. 相似文献
9.
A. A. Chernyshov K. V. Fel’de G. V. Bogatyreva P. V. Polyanskii M. S. Soskin 《Optics and Spectroscopy》2009,107(4):645-650
It is shown that, at an incoherent superposition of orthogonally polarized laser beams, a special type of singularities are
formed in the cross section of a combined beam in place of the well-known singularities, such as optical vortices (for scalar
fields); C points, at which the polarization is circular; and L lines, along which the polarization is linear (for coherent vector fields). These new singularities are U lines, along which the degree of polarization is zero and the state of polarization is undetermined, and P points, at which the degree of polarization is equal to unity and the state of polarization is determined by the nonzero
component of the combined beam. Conditions of topological stability of U and P singularities are discussed, as well as peculiarities of the spatial distribution of the degree of polarization of the field
in the vicinity of such singularities. First experimental results on the reconstruction of a vector skeleton formed by U and P singularities in combined speckle fields are presented. 相似文献
10.
Polarization properties of Gaussian Schell-mode type photon beams propagating through the non-Kolmogorov turbulence in a slant channel are studied which are based on the model of quantum field and the effective photon annihilation/creation operator. Our numerical results show that the degree of polarization increases with the increasing of the transverse coherent width of source ρs0, the source's transverse size ω0 and the power law of the turbulent spectrum, but the degree of polarization P decreases as the zenith angle θ increases. The effect of the wavelength of light beam on the degree of polarization of Gaussian Schell-model beams is small. 相似文献
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We have investigated the polarization state of a gated phase conjugate beam using a methyl-orange doped poly-vinyl alcohol (MO/PVA) film in 16 different combinations of linear and circular polarization states of a probe beam and pump beams. The experimental results agree with the theoretical prediction based on the Jones matrix method. Of the third-order nonlinear susceptibility tensors Xijkl of the MO/PVA film, the X1221 at the 647 nm wavelength in degenerate four-wave mixing under exposure of a gating 515 nm light takes a very small value compared with X1111 and X1122. On the other hand, in the configuration of a probe beam and pump beams having linearly crossed polarizations and without gating light, the MO/PVA film generates a strong linearly polarized PC beam, so that X1221 takes a large value at 515 nm. 相似文献
13.
Xiaoxu Lian 《Optics Communications》2011,284(22):5253-5258
Young's interference experiment is regarded as a two-slit diffraction phenomenon, the polarization singularities in Young's two-slit configuration illuminated with two linearly, orthogonally polarized Gaussian vortex beams are studied. It is shown that generally, there exist L-lines (linearly polarization) and polarization singularities including C-points (circular polarization), S23 and S31 singularities even though the parameters of two beams are the same. The pair creation-annihilation and motion of polarization singularities take place upon propagation, or by varying a control parameter, such as the amplitude ratio of two beams or obscure ratio of slits etc. For a special case of the illumination with two linearly, orthogonally polarized Gaussian vortex-free beams, polarization singularities, in particular, C-points may occur if a parameter of two beams is not equal. 相似文献
14.
The closed-form expression for the mean-squared width of apertured partially coherent beams propagating through turbulent media is derived by using the integral transform technique. The influence of turbulence on the spreading of apertured partially coherent beams is studied quantitatively by examining the relative mean-squared width, which is defined as the ratio of the mean-squared width of an apertured partially coherent beam in turbulence to the mean-squared width of the same beam in free space. On the other hand, the range of turbulence-independent propagation, also a reasonable measure of the resistance of a beam to turbulence, is obtained by examining the mean-squared width. It is shown that the spreading of apertured partially coherent beams is less affected by turbulence with smaller truncation parameter δ and coherence parameter α than with larger δ and α. In addition, the influence of turbulence on the spreading of apertured partially coherent beams increases first and then decreases due to increasing waist width w0. The results obtained are explained physically. 相似文献
15.
F.G. Mitri 《Ultrasonics》2009,49(8):794-798
Background and objective
Particle manipulation using the acoustic radiation force of Bessel beams is an active field of research. In a previous investigation, [F.G. Mitri, Acoustic radiation force on a sphere in standing and quasi-standing zero-order Bessel beam tweezers, Annals of Physics 323 (2008) 1604–1620] an expression for the radiation force of a zero-order Bessel beam standing wave experienced by a sphere was derived. The present work extends the analysis of the radiation force to the case of a high-order Bessel beam (HOBB) of positive order m having an angular dependence on the phase ?.Method
The derivation for the general expression of the force is based on the formulation for the total acoustic scattering field of a HOBB by a sphere [F.G. Mitri, Acoustic scattering of a high-order Bessel beam by an elastic sphere, Annals of Physics 323 (2008) 2840–2850; F.G. Mitri, Equivalence of expressions for the acoustic scattering of a progressive high order Bessel beam by an elastic sphere, IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control 56 (2009) 1100–1103] to derive the general expression for the radiation force function YJm,st(ka,β,m), which is the radiation force per unit characteristic energy density and unit cross-sectional surface. The radiation force function is expressed as a generalized partial wave series involving the half-cone angle β of the wave-number components and the order m of the HOBB.Results
Numerical results for the radiation force function of a first and a second-order Bessel beam standing wave incident upon a rigid sphere immersed in non-viscous water are computed. The rigid sphere calculations for YJm,st(ka,β,m) show that the force is generally directed to a pressure node when m is a positive even integer number (i.e. YJm,st(ka,β,m)>0), whereas the force is generally directed toward a pressure antinode when m is a positive odd integer number (i.e. YJm,st(ka,β,m)<0).Conclusion
An expression is derived for the radiation force on a rigid sphere placed along the axis of an ideal non-diffracting HOBB of acoustic standing (or stationary) waves propagating in an ideal fluid. The formulation includes results of a previous work done for a zero-order Bessel beam standing wave (m = 0). The proposed theory is of particular interest essentially due to its inherent value as a canonical problem in particle manipulation using the acoustic radiation force of a HOBB standing wave on a sphere. It may also serve as the benchmark for comparison to other solutions obtained by strictly numerical or asymptotic approaches. 相似文献16.
The closed-form expression for the angular spread of Gaussian Schell-model (GSM) array beams propagating through atmospheric
turbulence is derived. It is shown that the angular spread θ
sp of GSM array beams for the superposition of the cross-spectral density function is smaller than of those for the superposition
of the intensity. However, the θ
sp of GSM array beams for the superposition of the intensity is less sensitive to turbulence than that for the superposition
of the cross-spectral density function. For the superposition of the cross-spectral density function, θ
sp of GSM array beams with smaller coherence length σ
0, smaller waist width w
0, smaller beam number N, and larger separation distance x
d
are less affected by turbulence than of those with larger σ
0,w
0,N, and smaller x
d
; while, for the superposition of the intensity, the effect of turbulence on θ
sp is independent of N and x
d
. In addition, the angular spread is nearly the same for the two types of superposition when σ
0 or w
0 is small enough, or x
d
is large enough. On the other hand, it is found that there exist equivalent GSM array beams for the two types of superposition
which may have the same directionality as the corresponding fully coherent Gaussian beam in free space and also in turbulence. 相似文献
17.
Yuzhao Ma 《Optical Review》2012,19(2):39-44
We present an experimental setup to generate radially polarized beams without using high-cost optical elements. In the setup
a four-segment polarization converter is used in front of the fiber to produce a pseudo radially polarized beam. A traditional
step-index fiber which supports only LP01 and LP11 modes is then used as a mode-cleaning device. A commercial mechanical fiber-squeezer polarization controller is applied to
produce adequate pressure and twist onto the fiber. The four-segment polarization converter and the fiber squeezer polarization
controller are adjusted by turns for improving the beam quality in intensity and polarization. Additionally, several methods
of characterizing the polarization properties of radially polarized beams are reviewed. One of the latest methods is applied
for characterizing the polarization properties of the radially polarized beams produced by using our technique. The results
show the highquality of the obtained beams. 相似文献
18.
The dynamics of light-induced change in the refractive index of a resonant medium are examined. For illumination with weak fields, the two relevant relaxation times are T
1, the population lifetime and T
2, the dipole-dephasing time. The response time of the index change is determined by the slower relaxation time of the medium which is usually the time T
1 taken by the excited system to relax back to its thermal equilibrium value. Illumination with two beams of the same frequency that intersect within the medium leads to the formation of a volume grating in the medium that is spatially local. Hence there is no exchange of energy between the beams that write the grating, each beam merely reducing the absorption experienced by the other beam. Illumination with a moving, spatially periodic intensity pattern leads to gain for one beam and additional absorption for the other beam as they propagate through the medium. A complete set of coupled equations describing the intensities and phases of the beams undergoing non-degenerate two-wave mixing in the resonant media is derived using third-order perturbation theory, and the solutions are studied numerically. In particular, the two-beam coupling constant for intensity is shown to depend on the frequency difference between the two beams and on the pressure-induced collisional relaxations in the system. 相似文献
19.
采用积分变换的技巧,推导出了径向分布高斯列阵光束通过湍流大气传输的二阶矩束宽和远场发散角的解析公式,并详细研究了大气湍流对光束扩展和方向性的影响.研究表明,相干合成情况下,子光束数N越小、径向分布半径r0越大,列阵光束扩展受湍流影响越小.相干较非相干合成时列阵光束的扩展小,但非相干合成时列阵光束扩展受湍流的影响比相干合成时的小.特别地,N足够小或r0足够大时,相干与非相干合成列阵光束的远场束宽相等.另一方面,还给出了相干和非相干合成径向分布高斯列阵
关键词:
径向分布高斯列阵光束
大气湍流
相干和非相干合成
二阶矩束宽 相似文献
20.
Based on vectorial Debye theory, the focusing properties of partially polarized vortex beam by high numerical aperture Fresnel zone plate are investigated. The effects of the numerical apertures of and the phase difference of binary phase Fresnel zone plates, the topological charge of vortex beam and the degree of polarization of incident beam on the intensity distribution and degree of coherence in the focal plane are investigated in detail. It is shown that elliptical light spots and the flat top beam can be obtained by selecting certain parameters. Studies of degree of coherence reveal that the degree of coherence between x and y components of the electric field, which is zero in the source plane, is improved in the focal plane for vortex beam, but it is hardly changed for the nonvortex beam. It is also proved that any two of the three electric field components Ex, Ey and Ez are completely coherent everywhere in the focal region if the incident light beam is linearly polarized. 相似文献