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1.
利用偏振全息记录的方法在一种含偶氮侧链的液晶聚合物薄膜中写入了二维偏振光栅.实验采用两束正交偏振的532 nm线偏光作为写入光,在样品同一点上分别记录了相互垂直的两个一维偏振光栅,继而对所构成的二维偏振光栅的特性进行了研究.实验结果表明:二维光栅的衍射效率比一维光栅低,其偏振特性是两个一维光栅元特性的叠加;二维光栅衍射效率对入射光偏振态的依赖性和光栅的偏振转换性质来源于材料中线双折射和圆双折射的共同作用.
关键词:
偏振全息
二维光栅
偶氮液晶聚合物 相似文献
2.
R. S. Akopyan A. V. Galstyan G. G. Zakharyan N. F. Vardanyan Yu. S. Chilingaryan 《Technical Physics》2006,51(6):752-757
The diffraction and polarization properties of thick anisotropic holographic gratings recorded in polymer-dispersed liquid crystals are studied experimentally and theoretically. Such gratings are anisotropic and sensitive to temperature variations and also exhibit a strong dependence of the diffraction properties on the incident radiation polarization because of the presence of liquid-crystal molecules. The dependences of the diffraction efficiency and diffracted beam polarization orientation on the diffraction grating temperature and incident beam linear polarization are obtained for the case of Bragg incidence. The same dependences are derived using the known experimental temperature curves of the liquid crystal permittivity. The experimental data are in agreement with the theoretical calculations. The feasibility of controlling the diffraction characteristics of the grating in a wide temperature interval is demonstrated. 相似文献
3.
《中国光学快报(英文版)》2019,(8)
In this Letter, an all-optical logic sequence generator based on two different polarization holographic gratings has been proposed and demonstrated, which has one input port and four output ports. The polarization state of input light signal determines logic output signals. It can produce four kinds of logic sequence output signals:1000, 0100, 0010, and 0001, corresponding to the input light signal of four different polarization states: the p-linear, s-linear, left-handed circular, and right-handed circular. The two polarization gratings have been fabricated, and the working principle of the logic sequence generator has been proved by diffraction pattern analysis of polarization gratings. 相似文献
4.
A method of designing photonic crystal grating slow-wave circuit for Ribbon--Beam microwave travelling wave amplifiers 下载免费PDF全文
A method of designing a photonic crystal grating slow-wave circuit in which
the cylinders of the 2D photonic crystals dot on a cross-sectional plane is
established by calculating the band structures of the 2D photonic crystals,
and the eigenfrequency of the equivalent waveguide grating. For calculating
the band structures, the eigenvalue equations of the photonic crystals in
the system of photonic crystal grating slow-wave circuit are derived in a
special polarization mode. Two examples are taken to show the method. The
design result is validated by the scattering parameters of the same circuit.
The result indicates that there exists no photonic band gap if the metal
gratings do not extend into the photonic crystals; the design of the circuit
without the metal gratings extending into the photonic crystals is less
flexible than that with the metal gratings extending into the photonic
crystals. 相似文献
5.
We show, using rigorous diffraction theory, that resonance gratings can be used to transfer partial spatial correlation to partial polarization even if the incident light beam is fully polarized. The phenomenon is based on the fact that either of the two orthogonal polarization components can be coupled into the leaky waveguide mode, leading to a strong phase delay, while the other one is reflected without being coupled into the grating. Numerical demonstrations are based on a Gaussian Schell-model beam and a grating analysis performed by rigorous Fourier modal method. 相似文献
6.
Optimal design of sub-wavelength metal rectangular gratings for polarizing beam splitter based on effective medium theory 下载免费PDF全文
A novel optimal design of sub-wavelength metal rectangular
gratings for the polarizing beam splitter (PBS) is proposed. The
method is based on effective medium theory and the method of
designing single layer antireflection coating. The polarization
performance of PBS is discussed by rigorous couple-wave analysis
(RCWA) method at a wavelength of 1550~nm. The result shows that
sub-wavelength metal rectangular grating is characterized by a high
reflectivity, like metal films for TE polarization, and high
transmissivity, like dielectric films for TM polarization. The
optimal design accords well with the results simulated by RCWA
method. 相似文献
7.
采用模态法研究了共振域光栅分束器及闪耀光栅等光学器件的设计原理及逆向设计方法,给出了-1级非偏振闪耀光栅的典型设计示例。研究表明,自准直角入射时,光束在光栅内传输将激发产生离散模,通过调节离散模透过光栅传输时的累积相位差,可对衍射光进行调控,实现偏振(非偏振)分束、偏振(非偏振)闪耀等功能。采用严格耦合波法对基于模态法逆向设计的-1级非偏振石英闪耀光栅的几何参数进行验证,计算结果显示两者非常吻合,证明了该方法的正确性。 相似文献
8.
9.
光轴方向任意时光折变晶体中体全息光栅的衍射性质 总被引:2,自引:2,他引:0
利用坐标旋转方法和Kogelnik耦合波理论,建立了光轴方向任意时单轴晶体中体光栅布拉格衍射的耦合波方程,分析了Li NbO3晶体的光轴方向对光折变体全息光栅的各向同性和各向异性布拉格衍射性质的影响。模拟计算表明,在给定光栅的结构参量时,通过适当选择光轴方向角可以使得光折变体光栅的各向同性和各向异性布拉格衍射的衍射效率达到最大,给出了相应类型的衍射效率取得最大值时晶体光轴的大致方向。这些理论分析为光折变体全息光学器件的优化设计和进一步广泛应用提供了很好的理论参考依据。 相似文献
10.
New fabrication method for anisotropic gratings formed in photocrosslinkable polymer liquid crystals
We present a new fabrication method, called two-step ultraviolet exposure, to prepare anisotropic gratings in photocrosslinkable polymer liquid crystal films. Using the controllability of the reorientation direction of mesogenic molecules, anisotropic phase gratings, in which the mesogenic molecules were periodically modulated in orthogonal directions, were prepared by the use of one grating photomask. The resultant gratings diffract the light and convert the polarization states at the same time, and have applications as diffraction optical devices. PACS 42.65.Hw; 42.70.Df; 42.70.Nq; 78.20.-e; 78.40.Me 相似文献
11.
We have studied the optical transmission properties of a number of different dielectric diffraction gratings that each exhibit
two-dimensional chirality in their grating elements. We have found that the diffracted beams transmitted through these structures
exhibit large anisotropic polarization changes and polarization-dependent intensity modulations even though the chiral elements
are arranged in square grating arrays. The strength and functional form of both of these effects differ for each diffracted
beam. They are also dependent on the chirality of the surface patterning and the thickness of the patterned dielectric film.
We show how these properties could be exploited to provide a new and more versatile form of polarimeter, and how the operation
of such a device is inherently dependent on the optical non-reciprocity of these chiral gratings. 相似文献
12.
Diffraction of an ultrashort pulsed beam with arbitrary polarization state from a volume holographic grating in LiNbO3 crystals 下载免费PDF全文
Based on a modified coupled wave theory of Kogelnik, we have studied
the diffraction of an ultrashort pulsed beam with an arbitrary
polarization state from a volume holographic grating in
photorefractive LiNbO3 crystals. The results indicate that the
diffracted intensity distributions in the spectral and temporal
domains and the diffraction efficiency of the grating are both
changed by the polarization state and spectral bandwidth of the input
pulsed beam. A method is given of choosing the grating parameters and
input conditions to obtain a large variation range of the spectral
bandwidth of the diffracted pulsed beam with an appropriate
diffraction efficiency. Our study presents a possibility of using a
volume holographic grating recorded in anisotropic materials to shape
a broadband ultrashort pulsed beam by modulating its polarization
state. 相似文献
13.
Analysis on polarization dependence of Fraunhofer diffraction by metallic grating with short period 总被引:1,自引:0,他引:1
Min Ouyang Yang Cao Hua Gao Jinwei Shi Jing Zhou Dahe Liu 《Optics & Laser Technology》2008,40(1):201-207
A method based on the combination of finite-difference time-domain (FDTD) algorithm and Fourier transformation was proposed to analyze the Fraunhofer diffraction of gratings. Polarization dependence of the Fraunhofer diffraction of a one-dimensional metallic grating with period less than 8 times the incident wavelength was studied. Some special characteristics were found. The polarization dependence is related to period value, slit width, and thickness of the grating, and the missing orders predicted by scalar analysis appear. Besides, if the period of a grating is larger than 8 times the wavelength but the slit width or the size of the opaque portion of the grating is close to the wavelength, diffraction of the grating also becomes polarization dependent. 相似文献
14.
We demonstrate an innovative method for fabrication of high-spatial-frequency grating structures. This technique makes use of the near-field diffraction patterns from computer-generated phase holograms for lithographic fabrication of grating structures with periods that are one half that of the phase hologram mask. Linear, rectilinear, and circular gratings were fabricated with this technique. Experimental results from gratings with periods to 0.5 mum and feature sizes to ~0.2 mum are presented. 相似文献
15.
Orientation-controlled anisotropic diffraction gratings are realized by interferometric exposure using composite materials of nematic liquid crystals (LCs) and LC diacrylate monomers. The anisotropic diffraction properties in volume gratings, which dominantly diffract p- or s-polarized light, are shown to be controlled by the rubbed directions of the alignment layers under the control of the photopolymerization temperature. Images of the fringe patterns observed by polarization microscopy show the effects of the alignment layers on the LC orientation during grating formation. 相似文献
16.
We report the observation of polarization-independent photochromic diffraction in an azo-dye-doped liquid crystal. The generation of the phase grating is more than 90% independent of the polarization of the writing beams, and the diffraction by the phase grating is more than 90% independent of the polarization of the probe beam. Unpolarized lamp light was also used to generate real-time phase gratings and self-diffraction. For the first time to our knowledge, photochromic phase modulation and light diffraction that exhibit more than 90% polarization independence for both writing and probe beams were produced in an anisotropic liquid-crystalline material. 相似文献
17.
提出了一种利用数学变换来快速设计环形汇聚光栅反射镜的方法.通过分析具体的物理场景,抽象出已有条形汇聚光栅的"线"汇聚特性与所要设计的"点"汇聚特性在数学上对应的变换关系,然后用该数学变换对条形汇聚光栅进行外形上的变换,外形变换后的条形光栅即为可以实现"点"汇聚的环形光栅.用有限元算法对设计的环形汇聚光栅进行仿真,仿真证明采用该方法设计的环形光栅可以很好地实现高反、高汇聚.采用这一方法,设计了直径为29.788μm的环形光栅反射镜,当垂直入射的径向偏振光从设计的环形光栅表面反射回来后将发生汇聚,汇聚焦点位于环形光栅表面10μm处.经计算,反射镜的数值孔径为0.8302,反射率为0.9163,在焦点所在的汇聚面上,汇聚光栅电场分布的半高宽为1.5548μm. 相似文献
18.
19.
We present a unified design of wavelength-independent deep-etched fused-silica gratings as polarizing beam splitters and polarization-independent two-port beam splitters by using the simplified modal method. By defining unified grating parameters as the ratio of incident wavelength to grating period and the ratio of groove depth to grating period, unified grating structures are found to be approximately wavelength-independent, which is based on the modal view of the accumulated phase difference of two excited propagating grating modes. Diffraction efficiencies given by the rigorous coupled-wave analysis (RCWA) verified this unified design at the wavelength of 1064 nm. It should be noted that this unified design of wavelength-independent gratings is an analytic result, which is impossible to be derived with the well-known numerical RCWA. Modal method is powerful and presents a clear physical picture for us to obtain this unified design. Therefore, this unified design can be used as a general guideline for designing deep-etched fused-silica gratings as beam splitters for practical applications from ultraviolet to near infrared. 相似文献
20.
综合等效介质理论和表面等离子激元(SPP)Bloch模型,对比分析了两种新的亚波长光栅结构:二维矩形金属光栅和二维椭圆柱金属光栅。利用时域有限差分(FDTD)算法,对比分析了两种结构的透射率及其相位延迟与入射光波长及偏振角变化的关系,尤其两种结构实现λ/4波片功能所对应的透射特性。仿真结果表明,当入射光偏振角为75°时,两种结构均可实现λ/4波片功能,此时二维矩形和椭圆柱金属光栅的透射率分别为0.77和0.67,表明二维矩形金属光栅比椭圆柱光栅具有更好的透射效果。对应550~800nm的入射波长,两种光栅在各自允许的入射偏振角范围内均表现了较为平坦的宽带透射特性。 相似文献