共查询到20条相似文献,搜索用时 31 毫秒
1.
Polarization calibration unit(PCU) has become an indispensable element for solar telescopes to remove the instrumental polarization; the polarimetric accuracy of calibration depends strongly on the properties of PCU. In the paper, we analyze the measurement errors induced by PCU based on polarized light theory and find that the imperfections of the waveplate generate the main calibration errors. An optimized calibration method is proposed to avoid the effects from waveplate imperfections, and a numerical simulation is given to evaluate the polarization accuracy by analyzing the relation between calibration error and intensity instability. The work is very important for solar telescopes with high polarization precision up to 10~(-4) I_c. 相似文献
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极化转换是电磁波调控的重要研究方向之一.本文基于场变换理论提出一种宽入射角的宽带毫米波半波片.基于等效媒质理论,该半波片可由亚波长厚度的两种介电常数不同的材料周期性排布后旋转45°得到.通过设计控制两种材料的介电常数、高度比值以及整个半波片的厚度可以在毫米波段实现极化转换的功能,此设计具有低损耗和高转化效率的特点.此半波片能实现横电波与横磁波的相互转换以及圆极化波的相互转换,极化转换-3 dB相对带宽达49%.仿真和实测结果相符,验证了该半波片宽带高效的极化转换效果.在入射角为60°时,极化转换-3 dB带宽依然能够达到36%左右. 相似文献
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基于双折射晶体的光交叉波分复用器 总被引:6,自引:0,他引:6
光交叉波分复用器能够把一组DWDM光信号分解成两组奇偶信道输出 ,或反之。双折射晶体的设计关健部分由两个光轴成 45°的波片A和B组成。入射光信号经过偏振分束器和偏振元件处理后 ,在A波片中形成o光、e光并产生位相差。在B波片中再次分解并发生干涉形成奇偶信道光输出。A波片厚度决定位相差从而决定输出信道间隔。用两片光轴垂直或相同但不同材料的波片按一定的厚度组合代替波片A可消除输出频率间隔的温度漂移。基于双折射晶体的设计是实现商用化光交叉波分复用器的有效途径。 相似文献
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研究了一种新型模拟双折射结构DWDM滤波器的中心频率和带宽的可调谐特性.研究表明:当给定满足一定平坦化要求的光谱透射率所需的各模拟波片中偏振旋转器的旋转角时,通过模拟波片中楔形介质对的相对位移来调节光在各模拟波片中的光程差,同时保持光程差仍满足特定的比例关系,可实现中心频率及带宽的调谐.当光在各模拟波片中的光程差变化较小时,可实现中心频率的调谐,此时带宽的改变很小,可忽略不计;随着光程差变化的不断增大,带宽的改变则不能忽略. 相似文献
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Yunfeng Bai 《Optics Communications》2011,284(19):4272-4274
A novel polarization measurement approach using multi-slit diffraction method is proposed in this paper. Part of binary grating is covered by one polarizer. And based on Fraunhofer diffraction, the diffraction intensity formula is deduced. Then we can get the polarization state of the incident light by fitting the measured diffraction pattern with theory diffraction intensity formula. This method only uses polarizer, but not 1/4 waveplate, therefore, it can be applied to measure monochromatic light of any wavelength without a replacing device. 相似文献
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A CCD-based polarization interferometric technique is developed to test waveplates. A Babinet compensator is used to produce interference fringes for polarized input and the retardance introduced by the waveplate when inserted in the optical beam is calculated from the fringe shifts using the phase matching technique. A theoretical model is fitted with the observed fringe shifts to get an accuracy of 0.5° in the retardance calculation. The experimental set-up and the measurement of retardance for zero-order and high-order quarter waveplates are discussed. The retardance calculation for a zero-order waveplate is found to be more accurate than the high-order waveplate. This technique can also be used to measure an arbitrary amount of retardance produced by any birefringent waveplate and also to determine its optic axis direction. 相似文献
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利用1/4波片调整左、右旋偏振光的理论研究 总被引:4,自引:2,他引:2
首先利用斯托克斯矢量法分析了一束自然光通过起偏器和 1/ 4波片后的偏振态 ,指出了出射光偏振态变化的原因 ,然后将起偏器和 1/ 4波片二者之一固定 ,转动另一器件来分析出射光的偏振态变化 ,找出了出射光是左旋偏振光还是右旋偏振光的分界点 ,并由此推导出了将左 (右 )旋偏振光调为右 (左 )旋偏振光的新方法 相似文献
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《中国光学快报(英文版)》2017,(5)
An elliptical initial polarization state is essential for generating mode-locked pulses using the nonlinear polarization rotation technique. In this work, the relationship between the ellipticity ranges capable of maintaining mode-locked operation against different pump power levels is investigated. An increasing pump power, in conjunction with minor adjustments to the polarization controller's quarter waveplate, results in a wider ellipticity range that can accommodate mode-locked operation. Other parameters such as noise, pulsewidth, and average output power are also observed to vary as the ellipticity changes. 相似文献
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Generation and Modulation of Phase Difference of Output Intensities in a Feedback Nd:YAG Laser with an Extracavity Waveplate Rotated 总被引:1,自引:0,他引:1 下载免费PDF全文
External anisotropic feedback effects on the phase difference behaviour of output intensities in a microchip Nd:YAG laser are presented. By rotating a quarter wave plate placed in the external cavity, the angle between laser initial polarization direction and o-axis of the wave plate is tuned from -45°to 45°, which results in variable extra-cavity birefringence along two orthogonal detection directions. With only one optical path and one wave plate, laser intensities of the two orthogonal directions, both modulated by the external cavity length, are output with a tunable phase difference, which can be continuously changed from zero to twice as large as that of the waveplate. Experimental results as well as a theoretical analysis based on Fabry-Perot cavity equivalent model and the refractive index ellipsoid, are presented. The potential applications of this phenomenon are also discussed. 相似文献
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Toshihiro Mino Yuika Saito Hiroyuki Yoshida Satoshi Kawata Prabhat Verma 《Journal of Raman spectroscopy : JRS》2012,43(12):2029-2034
Polarization‐dependent Raman microscopy is a powerful technique to perform both structural and chemical analyses with submicron spatial resolution. In conventional Raman microscopy, the polarization measurements are limited only in the direction parallel to the sample plane. In this work, we overcome the limit of conventional measurements by controlling the incident polarization by a spatially modulated waveplate. In this method, the polarization perpendicular to the sample surface (z‐polarization) can be detected together with the parallel polarization (xy‐polarization). Because of this unique polarization control, our Raman microscope has the ability to image the molecular orientation, together with the molecular analysis. Here, we have investigated thin films of pentacene molecules that are widely studied as an organic semiconductor material. The orientations of pentacene molecules are imaged with a spatial resolution of 300 nm. Our results clearly indicate that the lamellar grains show the lower tilt angles compared to the neighboring islands, which has not been proved in conventional methods. The substrate effects and the thickness dependence of the film are also studied. These results provide knowledge about the relationship between the devise performance and the film structures, which is indispensable for future device exploitations. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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A detailed analysis of the polarization eigenmodes of a QHQ retarder (a half-wave plate sandwiched between two identical quarter-wave plates) is presented. These are shown to be discontinuous as a function of the orientation of the half-wave plate, as a function of the wavelength of incident light and as a function of the retardation of the middle waveplate. 相似文献
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Two-wave mixing (TWM) in transmission geometry of photorefractive (PR) crystals of 23 symmetry such as BSO, BGO is investigated by solving a set of coupled wave equations and taking their optical activity as one of the effective parameter. Coupled wave equations are solved numerically by fourth order Runge-kutta method and results are presented in graphical form. The effects of various parameters such as crystal thickness, optical activity, coupling coefficient, absorption, and input polarization angle of pump beam has been studied on the input beam polarization components. It has been observed that by varying the behaviour of pump beam polarization, signal beam can be modified. This can be used in various applications such as spatial light modulation and optical information processing, etc. 相似文献
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Ignacio Moreno Pablo Velásquez Daniel Puerto Asticio Vargas 《Optics Communications》2006,260(1):12-18
In this work, we show a very simple birefringent filter useful to modulate a broadband light spectrum. We first show the generation of various oscillating spectra using two identical multiple-order waveplates. In particular a sinusoidal broadband spectrum with a rapid oscillation is obtained. This spectrum is amplitude modulated by adding another waveplate to the system. This waveplate has a small phase shift, and with the proper orientation generates amplitude beats on the broadband spectrum. Finally, we show how this system can be voltage controlled by means of a ferroelectric liquid crystal modulator. We experimentally demonstrate this behavior with the aid of a portable spectrophotometer, and we provide a theoretical explanation on the basis of the Jones matrix formalism. 相似文献
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Broadband Terahertz Polarization Converter and Asymmetric Transmission Based on Coupled Dielectric‐Metal Grating 下载免费PDF全文
Coupled dielectric‐metal gratings are investigated for broadband terahertz (THz) wave polarization conversion and asymmetric transmission by the experiments and numerical simulations, which are composed of the subwavelength Si grating and metallic wire grating layers. The dielectric grating layer with a large artificial birefringence and low dispersion is employed as a phase engineered waveplate, and the metal wire grating arranged with a 45° angle to the dielectric grating is utilized as a high‐efficiency polarizer. Due to the subwavelength integration, this coupled grating presents a local resonance coupling mechanism between dielectric and metal gratings, which greatly enhances the polarization rotation and expands the bandwidth, not a simple combination with dielectric and metallic gratings. The results demonstrate that a broadband asymmetric transmission with an extinction ratio of 30dB from 0.2 to 1.2 THz is achieved and the highest transmission of 90% can be obtained. It provides a simple way towards practical applications for THz artificial dispersion materials, polarization control and asymmetric transmission. 相似文献
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利用旋转波片组实现偏振变换器的两种新方法 总被引:4,自引:1,他引:3
偏振变换器作为一种重要的光学器件.以其高偏振变换精度、低成本、低插入损耗以及控制算法简单的特性在相干光纤通信和高速光纤通信领域具有十分重要的地位。提出了利用两个λ/4波片和一个λ/2波片的三波片组合实现任意偏振态变换的新方法。用改进的三维庞加莱球方法—偏振态投射平面的二维几何方法分别推导出了λ/4 λ/4 λ/2组合以及λ/2 λ/4 λ/4组合实现任意偏振态变换时每个波片的位置参量计算公式。研究结果表明:两个λ/4波片和一个λ/2波片的任意组合都可以实现任意偏振态的变换;用偏振态投射平面的几何方法处理偏振变换的相关问题比庞加莱球方法和矩阵处理方法简洁明了。研究结果为偏振变换器的设计提供了理论依据。 相似文献
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Yandong Gong Banghong Zhang Takashi Notake Hiroaki Minamide Malini Olivo Shigeki Sugii 《Applied Physics A: Materials Science & Processing》2014,115(1):83-86
A polarimetric Terahertz frequency-domain spectroscopy system is presented which has an additional polarization measurement function at the Terahertz band. The achromatic Terahertz waveplate, which acts as the key device in the system, is also presented. 相似文献
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A blind-angle calibration method is introduced for self-spectral calibration of a compound zero-order waveplate. By rotating the waveplate at blind detection angles, the wavelength-dependent retardance and the orientation of the effective fast axis can be determined through iterative least-squares calculations of the spectra measured by a multi-channel spectrometer. Excellent agreement between the experimental values and the theoretical values is achieved, indicating that the new method can be used as a reliable way to calibrate compound zero-order wave plates. Using the new method, there is no need to rotate the waveplate at specific detection angles. A high-precision waveplate holder or complex adjustment procedure is not required. 相似文献