共查询到19条相似文献,搜索用时 93 毫秒
1.
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
2.
多光束全息互连元件往往需要大量的耦合波方程才能描述。本文通过分析记录时生成的互调制光栅的性质及其对衍射的影响,对问题进行适当的简化。通过解不同条件下的耦合波方程、分别给出了多光束全息图在各种不同情况下的衍射效率的近似解析表达式,展示了衍射效率与各实验参量之间的关系。为进一步研究多光束全息互连元件的性质、比较各种条件下的效率以及各参量对总体效率的影响,提供了方便。 相似文献
3.
基于严格耦合波理论建立了多层介质膜光栅的衍射机理模型,给出了TE波自准直条件下多层介质膜光栅衍射效率的表达式.以-1级衍射效率为评价函数,分析了表面浮雕结构分别为HfO2和SiO2材料的介质膜光栅获得衍射效率优于96%的结构参数.数值计算表明,顶层材料为HfO2的介质膜光栅具有更宽的结构选择范围.最后分析了介质膜光栅的制备容差和允许的入射角度范围.
关键词:
衍射效率
多层介质膜光栅
严格耦合波理论 相似文献
4.
静磁波与导波光的磁光耦合理论 总被引:6,自引:2,他引:4
根据耦合模理论,分析了砂光波导中静磁波与导波光的相互作用特点。给出了导波光模式之间的耦合方程。理论分析表明,仅当垂直磁化时,发生模式转换的导波光材被全部衍射,此时衍射效率等于模式转换效率。计算了斜向场作用下YIG薄膜中导波光的反斯托克斯相互作用衍射效率,所得结论与实验结果一致。适当倾斜静磁场,导波光的模式转换和衍射效率均可比垂直磁化时间显提高。同时改变静磁体波传播方向和斜向场的偏离方向(与垂直方向 相似文献
5.
6.
7.
利用一维耦合波理论研究了入射方向相互垂直的一束平面波与一束柱面波干涉形成光折变局域体全息光栅的波前转换情况。给出了透射波和衍射波振幅的解析表达式。讨论了该局域体全息光栅的几何尺寸以及全息透镜的焦距对光栅衍射效率的影响。结果表明,随着光栅横向尺寸的增加,光栅的衍射效率也逐渐增加。然而,光栅的衍射效率却随着光栅纵向尺寸的增加而减小。全息透镜的焦距越长,光栅的衍射效率也越大。此外,分析了光栅的布拉格选择特性,该光栅具有非常好的角度选择特性。在平面波与柱面波干涉形成全息透镜的设计中,为了获得最优的衍射效率,应当根据要求合理地选择记录所用柱面波和设计光栅的几何尺寸。 相似文献
8.
9.
基于对体光栅衍射效率的计算分析,本文直接地、精细地讨论了体光栅的功率守恒问题.结果指出:弱耦合前提假定下的双波耦合波二阶理论,不能严格地满足能量平衡准则. 相似文献
10.
11.
The diffraction properties of reflection volume holographic gratings are studied when the gratings are illuminated by an ultrashort beam with arbitrary temporal profiles. The modified Kogelnik's theory of coupled waves is used. Simple analytical expressions for spectral and temporal distribution of the transmitted and diffracted are obtained. The dependences of the diffraction bandwidth, the Bragg selectivity bandwidth and the total diffraction efficiency of the reflection volume grating on the temporal profiles of the input ultrashort pulse are investigated. Study shows that the bandwidth of the reflection volume holographic gratings varies with the grating parameters more slowly than the transmitting volume holographic gratings. For three different temporal profiles, numerical results about diffraction properties of the reflection volume holographic gratings are given and compared with the transmitting volume holographic gratings. 相似文献
12.
13.
We demonstrate edge-enhanced imaging produced by volume phase gratings recorded on a polyvinyl alcohol/acrylamide photopolymer. Bragg diffraction, exhibited by volume gratings, modifies the impulse response of the imaging system, facilitating spatial filtering operations with no need for a physical Fourier plane. We demonstrate that Kogelnik's coupled-wave theory can be used to calculate the transfer function for the transmitted and the diffracted orders. The experimental and simulated results agree, and they demonstrate the feasibility of our proposal. 相似文献
14.
P. St. J. Russell 《Applied physics. B, Lasers and optics》1981,26(1):37-42
Novel thick grating focussing and de-focussing devices are described which employ uniform phase gratings with special boundary shapes. The analysis used is based upon an eigenmodal approach to Kogelnik's coupled-wave equations, akin to the dynamical theory of x-ray diffraction. The relationship between the direction of phase progression of the coupled-waves at Bragg incidence, and the direction of the Poynting vector is carefully delineated. As a consequence, a new technique-Poynting Vector Optics — is suggested as potentially an important means of designing thick gratings to fulfil certain beam processing roles, especially in integrated optics applications. The two-dimensional coupled-wave equations are briefly employed to illustrate the effectiveness of a particular focussing device. 相似文献
15.
Diffraction gratings have been an interesting field during the last decades. A great deal of research has been done in order to understand how light propagates inside diffraction gratings. Since its formulation, the Rigorous Coupled Wave Theory (RCWT) has been applied to different periodic structures providing a basis to check the validity of approximate theories, such as Kogelnik's coupled wave theory or the coupled wave theory neglecting second derivatives. In this work we will compare the results of the diffraction efficiencies of the first and second orders at second on-Bragg replay angular condition, obtained by using an analytical formula provided by Alferness using an approximate thin-matrix decomposition method (TMDM) with the results obtained by using the RCWT. Good agreement between the results obtained using TMDM and the RCWT were found. 相似文献
16.
Based on Kogelnik's coupled wave theory, the time-domain diffraction and transmission of static PR gratings are theoretically studied when they are illuminated by ultra-short pulse laser. Study shows that the waveforms of the diffracted and transmitted pulses depend on the readout pulse duration, grating spacing, crystal thickness and refractive index modulation. By changing the values of these parameters, the diffracted and transmitted waveforms can be controlled. Also we find there is a displacement of diffracted and transmitted pulse along the time-axis when compared to readout pulse. Conclusions of our study could be used in many areas, such as pulse shaping and signal processing. 相似文献
17.
18.
19.
Over the last 20 years, dichromated gelatin has been considered to be the best holographic recording material. However, the non-reproducibility of results in relation to light sensitivity, for a large number of experimental factors, restricted the use of this material. In this work, we consider the refractive index modulation profile and its stability. We propose a mixed method using Kogelnik's coupled wave theory (an approximate theory) and an alternative theory of diffraction in modulated media (an exact theory). The aim of this contribution is to use this mixed method in order to study the evolution of the modulation profile in correlation with the modification of the chemical environment during the final stage of processing. In our study we compare the effect of different kinds of final processing baths on the refractive index modulation profile. In order to characterize our holograms we have developed an experimental set-up for diffractive elements analysis. The experimental results are compared with the theoretical ones. For the numerical study we have carried out a complete set of numerical computations by using our own programs. These programs are based on a complete and exact solution of the Maxwell equations. 相似文献