共查询到20条相似文献,搜索用时 46 毫秒
1.
A stochastic electromagnetic array beam that is generated by an electromagnetic Gaussian Schell-model source is introduced
by using tensor method. An analytical expression for the cross-spectral density matrix of the stochastic electromagnetic array
beam propagating in a paraxial ABCD optical system is derived after performing vector integration. Some numerical calculations are illustrated for the propagation
characteristics of such an array beam in free space and fractional Fourier transform (FRFT) system as application examples. 相似文献
2.
一阶光学系统分数傅里叶变换的相空间分析 总被引:1,自引:0,他引:1
在维格纳相空间中,通过将一阶光学系统的传输矩阵分解为坐标旋转、比例缩放和啁啾矩阵的组合,得到了一阶光学系统在空域的分数傅里叶表示.结果表明:任意一阶光学系统均可表示为经过比例缩放和二次相位调制的分数傅里叶变换.通过将输入输出光场在相空间中作π/2角旋转,得到了一阶光学系统在频域的传输矩阵和衍射积分公式,进而得到了一阶光学系统在频域的分数傅里叶表示.比较空域和频域一阶光学系统的相空间变换矩阵,说明2个系统本质上属同一变换在不同基坐标下的表示,并推导出了光学系统在空域和频域具有相同分数傅里叶变换的条件. 相似文献
3.
The analytical propagation expression of partially coherent flat-topped vortex beams through a paraxial optical ABCD system is derived, and it then is used to investigate the coherence vortex properties of partially coherent flat-topped vortex
beams in the Fourier transform and fractional Fourier transform systems. It is shown that in the Fourier transform system
the coherence vortex depends on the flat-topped beam order N, spatial coherence parameter α and position (x
1,y
1) of the reference point, whereas in the fractional Fourier transform system the flat-topped beam order N does not affect the spectral degree of coherence. Furthermore, in both transform systems, depending on the choice of the
reference point, the zero value point of the spectral degree of coherence may be present or absent. In particular, if x
1=y
1=0 is selected, the phase at the zero value point of the spectral degree of coherence may be determinate; thus the coherence
vortex does not exist. 相似文献
4.
Kurtosis parameters of super Lorentzben Gauss beams through a paraxial and real ABCD optical system 下载免费PDF全文
Based on the propagation equation of higher-order intensity moments, analytical propagation expressions for the kurtosis parameters of a super Lorentz-Gauss (SLG) SLG01 beam through a paraxial and real ABCD optical system are derived. By replacing the parameters in the expressions of the kurtosis parameters of the SLG01 beam, the kurtosis parameters of the SLG10 and SLG11 beams through a paraxial and real ABCD optical system can be easily obtained. The kurtosis parameters of an SLG01 beam through a paraxial and real ABCD optical system depend on two ratios. One is the ratio of the transfer matrix element B to the product of the transfer matrix element A and the diffraction-free range of the super-Lorentzian part. The other is the ratio of the width parameter of the super-Lorentzian part to the waist of the Gaussian part. As a numerical example, the properties of the kurtosis parameters of an SLG01 beam propagating in free space are illustrated. The influences of different parameters on the kurtosis parameters of an SLG01 beam are analysed in detail. 相似文献
5.
By introducing a hard aperture function into a finite sum of complex Gaussian functions, an approximate analytical expression for the two-dimensional off-axial Hermite-cosh-Gaussian beams passing through a rectangular apertured and misaligned paraxially ABCD optical system has been derived. The results provide more convenience for studying their propagation and transformation than the usual way by using diffraction integral directly. Some numerical simulations are also illustrated for the propagation characteristics of a two-dimensional off-axial Hermite-cosh-Gaussian beam through a rectangular apertured ABCD optical system. 相似文献
6.
7.
By using the beam coherence-polarization (BCP) matrix approach, analytical propagation equations of partially polarized Gaussian Schell-model (PGSM) beams through an axis-unsymmetric paraxial optical ABCD system are derived, which enable us to study the propagation-induced polarization changes and irradiance distributions at any propagation distance of PGSM beams through axis-unsymmetric systems within the framework of the paraxial approximation. Detailed numerical results for a PGSM beam passing through a bifocal lens are presented to illustrate the propagation properties of PGSM beams. A comparison with the previous work is also made. 相似文献
8.
Based on the Collins integral formula and the Hermite–Gaussian expansion of a Lorentz function, an analytical expression for
the Wigner distribution function (WDF) of Lorentz and Lorentz–Gauss beams through a paraxial ABCD optical system is derived. The properties of the WDF of Lorentz and Lorentz–Gauss beams propagating in free space are demonstrated.
The normalized WDFs of Lorentz and Lorentz–Gauss beams at the different spatial points are depicted in the several observation
planes. The influences of the beam parameters on the WDF of Lorentz and Lorentz–Gauss beams in free space are also analyzed
at different propagation distances. The special WDF of a Lorentz beam results in its higher angular spreading than the Gaussian
beam. 相似文献
9.
Guohua Wu Qihong Lou Jun Zhou Jingxing Dong Yunrong Wei Zhouping Su 《Optics & Laser Technology》2008,40(3):494-498
The propagation of flat-topped beams passing through paraxial ABCD optical system is investigated based on the propagation formulas of Gaussian beam. The focal shift of focused coherent flat-topped beam is also studied in detail. Analytical expressions of the M2 factor and the far-field intensity distribution for flat-topped beams are derived on the basis of second-order moments. 相似文献
10.
An approximate analytical propagation formula of the elliptical Gaussian beams through a paraxial ABCD optical system with a circular aperture is obtained on the basis of the expansion of a hard-edged aperture into a finite sum of complex Gaussian functions. And the parameter characteristics of the truncated beams including the beam propagation factor and the kurtosis parameter are also studied in detail by using the second-order-moments method. 相似文献
11.
Combining the ABCD transfer matrix and the generalised Huygens-Fresnel integral equation method, the closed-form expression of a finite Airy Gaussian array beam (FAGAB) threading through a paraxial optical system was established in a space domain. We systematically investigated the evolution of the FAGAB's properties travelling through a curved slab system based on previously derived formula. The wave's characteristics through the flat slab system were the special cases of the main findings. We also assess the influence of the truncation factor and adjustment parameter on the FAGAB's intensity distribution on the slab system model's input and output cross-sections. 相似文献
12.
A. Chafiq 《Optics Communications》2006,265(2):594-602
Using Collins formula and the expansion of Mathieu beams in terms of Bessel beams we derive the exact propagation equations of Mathieu-Gauss beams through an apertured paraxial ABCD optical system. A comparison between the exact propagation equations and the approximated ones, which are derived by expanding the circ function into a finite sum of Gaussian functions, is presented. The propagation characteristics of zeroth-order Mathieu-Gauss beams in (y-z) and (x-z) planes are analyzed with detailed numerical calculations. It is found that the profile of the propagated Mathieu-Gauss beam is similar to that of Bessel-Gauss beam. Furthermore, the focalization of the Mathieu-Gauss beams through a thin lens is illustrated and analyzed with numerical results. 相似文献
13.
Optical encryption by double-random phase encoding in the fractional Fourier domain 总被引:23,自引:0,他引:23
We propose an optical architecture that encodes a primary image to stationary white noise by using two statistically independent random phase codes. The encoding is done in the fractional Fourier domain. The optical distribution in any two planes of a quadratic phase system (QPS) are related by fractional Fourier transform of the appropriately scaled distribution in the two input planes. Thus a QPS offers a continuum of planes in which encoding can be done. The six parameters that characterize the QPS in addition to the random phase codes form the key to the encrypted image. The proposed method has an enhanced security value compared with earlier methods. Experimental results in support of the proposed idea are presented. 相似文献
14.
Juguan Gu Juguan Gu Daomu Zhao Zhangrong Mei Zhangrong Mei Haidan Mao Haibin Xu 《Optik》2004,115(11-12):529-532
By means of Collins diffraction integral formula in the paraxial approximation and based on the fact that a hard aperture function can be expanded into a finite sum of complex Gaussian functions, an approximate analytical expression for linearly polarized Bessel-Gaussian beams passing through a paraxial ABCD optical system with an annular aperture has been derived. The results provide more convenient for studying their propagation and transformation than the usual way by using diffraction integral directly. By using the analytical expression and the diffraction integral formula some numerical simulations are done to illustrate for the propagation characteristics of a linearly polarized Bessel-Gaussian beam through an optical system with an annular aperture. 相似文献
15.
Fractional Fourier transform for partially coherent beam in spatial-frequency domain 总被引:1,自引:0,他引:1 下载免费PDF全文
By using Fourier transform and the tensor analysis method, the fractional Fourier transform (FRT) in the spatial-frequency domain for partially coherent beams is derived. Based on the FRT in the spatial-frequency domain, an analytical transform formula is derived for a partially coherent twisted anisotropic Gaussian-Schell model (GSM) beam passing through the FRT system. The connections between the FRT formula and the generalized diffraction integral formulae for partially coherent beams through an aligned optical system and a misaligned optical system in the spatial-frequency domain are discussed, separately. By using the derived formula, the intensity distribution of partially coherent twisted anisotropic GSM beams in the FRT plane are studied in detail. The formula derived provide a convenient tool for analysing and calculating the FRTs of the partially coherent beams in spatial-frequency domain. 相似文献
16.
The symmetrizing transformation of coherent general astigmatic Gaussian beams is analysed by the tensor ABCD law. It is shown in this paper that a nonorthogonal astigmatic Gaussian beam (with rotation) can be transformed into a rotationally symmetric one by the combination of four cylindrical lenses. A simple example is given. 相似文献
17.
A new form of laser beams called four-petal Gaussian beams is introduced. Based on the Collins integral, two kinds of analytical propagation expressions for this new kind of beams through a paraxial ABCD optical system are derived. The propagation properties of the four-petal Gaussian beams are studied and illustrated with numerical examples. At the source plane the beam has four-petals; the space among the petals is determined by the beam order. In the far field the beam evolves into a number of mirror symmetric petals and the petals of higher order beams can be equally spaced. 相似文献
18.
Xinyue Du 《Optics Communications》2008,281(10):2711-2715
When random electromagnetic beams passing through axially nonsymmetrical ABCD optical systems, the analytical formula for the transformation of the elements of 2 × 2 cross-spectral density matrix is obtained with the help of vector integration. We derive analytical expressions of the spectral degree of polarization, the spectral degree of coherence, and the spectral density in any output plane z > 0. Some numerical calculations are illustrated relating to the electromagnetic Gaussian Schell-model beams propagating through such optical systems. 相似文献
19.
Propagation of relative phase shift of apertured Gaussian beams through axisymmetric optical systems
When a Gaussian beam is apertured, it undergoes a phase shift as well as a focal shift. The relative phase shift of an apertured Gaussian beam through an axisymmetric optical system written in ABCD matrix is analyzed by applying Collins' diffraction integral formula. And, more important, the condition of dispeling the relative phase shift is obtained, which is related with the Fresnel number. At last, some extensions are given. 相似文献
20.
By expanding the hard-aperture function into a finite sum of complex Gaussian functions, we derive approximate analytical formulae for Lorentz and Lorentz-Gauss beams propagating through an apertured fractional Fourier transform (FRT) optical system. As an application example, properties of a Lorentz-Gauss beam in the FRT plane after propagating through a squarely or annularly apertured FRT optical system are studied numerically. The results obtained using the approximate analytical formula are in good agreement with those obtained using numerical integral calculation. The FRT optical system provides a convenient way for laser beam shaping. 相似文献