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This Letter introduces and discusses a difference in the behavior of a cylindrical diffractive lens encoded with subwavelength structures illuminated with monochromatic coherent light in the cases of TE and TM polarization. The effective medium theory is used to model with new binary phase function the diffractive lens. A new algorithm combines the finite-difference time domain for the propagation in the near field and the radiation spectrum method for the propagation in the far field. We observe the existence in the TM polarization of a second spot at half the distance of the focal length not predictable by scalar theory. 相似文献
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有限口径非周期亚波长衍射聚焦偏转器的严格矢量优化 总被引:1,自引:0,他引:1
有限口径非周期亚波长衍射光学器件的亚波长结构特性使得传统标量衍射理论失效,必须借助严格电磁理论进行器件的设计。提出一种循环平面波谱算法(IterativePlaneWaveSpectrumAlgorithm,IPWSA)作为器件优化算法,利用二维时域有限差分方法作为严格电磁计算模式,根据Farn方法对器件面型进行亚波长处理,设计出有限口径非周期具有亚波长结构的衍射聚焦偏转器件,偏转角为24.8°,该器件可与激光器集成构成微型集成光学系统,也可以用在红外量子阱系统中。详细分析了算法原理,设计实例验证了算法的优化效果。 相似文献
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Paraxial-domain diffractive elements with 100% efficiency based on polarization gratings 总被引:1,自引:0,他引:1
The concept of polarization freedom is employed to design diffraction gratings that are capable of transforming an electromagnetic plane wave into two or three diffraction orders with an arbitrary efficiency distribution among them, such that the combined efficiency of the signal orders is always equal to 100%. As a special case we consider paraxial-domain duplicators and triplicators with 100% efficiency, which is not possible for illumination by scalar waves: Diffractive elements that are capable of performing the required wave transformation must modulate the state of polarization of the incident field. 相似文献
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We describe the fabrication and characterization of a nanostructured diffractive element with near-zero reflection losses. In this element, subwavelength nanostructures emulating adiabatic index matching are integrated on the surface of a diffractive microstructure to suppress reflected diffraction orders. The fabricated silicon grating exhibits reflected efficiencies that are suppressed by 2 orders of magnitude over broad wavelength bands and wide incident angles. Theoretical models of the fabricated structure based on rigorous coupled-wave analysis and effective medium theory are in agreement with the experimental data. The proposed principles can be applied to improve the performance of any diffractive structures, potentially leading to more efficient Fresnel lenses, holographic elements, and integrated optical systems. 相似文献
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This paper presents methods for designing and recording optimal computer-generated diffractive optical elements. The design method is based on an analytic ray-tracing procedure for minimizing aberrations. The recording involves computer-generated masks and multiple lithographic processes in order to form reflective and transmissive multilevel, surface relief-phase, diffractive elements. As a result, the elements can have high diffraction efficiencies over a broad range of incidence angles. Even generalized diffractive elements that operate with highly uniform diffraction efficiency and polychromatic radiation can be designed and recorded by optimizing the shape and height of the relief gratings. To illustrate the effectiveness of the diffractive optical elements, they have been incorporated into a number of applications, involving visible as well as infra-red radiation. Some that deal with coordinate transformation, beam shaping, and polarization control are briefly reviewed. 相似文献
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传统方格型二维光栅与周期性缝隙阵列的组合薄膜结构具有雷达和光学波段双带通的电磁特性. 但由于其杂散光能量集中分布而严重制约它在高精度探测以及成像领域中的应用. 本文提出了一种全新的组合薄膜结构, 即由满足一定约束条件的圆孔型二维光栅和十字缝隙阵列构成. 基于Fraunhofer衍射理论建立组合薄膜结构标量衍射模型, 通过对比两种组合薄膜结构的衍射光分布, 理论分析与实验测试均表明: 圆孔型光栅与十字缝隙阵列组合薄膜结构不仅能够提高其光学透过率, 而且还使其杂散光分布均匀, 降低了其杂散光总比率, 从而有效抑制杂散光, 进一步增强了二维光栅与周期性缝隙阵列组合薄膜结构在实际光学系统中的可靠性.
关键词:
二维光栅
组合薄膜结构
衍射光强
杂散光 相似文献
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在分析单层和多层衍射元件衍射效率的基础上,推导出光学系统中多层衍射元件浮雕深度和基底材料的一般关系式,并对这些变量进行优化,得到阿贝数的值大致在20~80之间,β的合理值在0.25~0.6之间,当2个衍射元件的阿贝数v1<v2,且差值比较大时,阿贝数小的衍射元件的基底材料选择光学玻璃中的火石玻璃,阿贝数大的衍射元件的基底材料选择光学玻璃中的冕牌玻璃。根据这个方法,设计了3组可实现宽波段高衍射效率的不同材料、不同浮雕深度的组合,使得每组组合中两层衍射元件的衍射效率都在99%以上。 相似文献
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标量衍射理论形式简洁,有很高实用性,但是在衍射微光学元件分析中显得模型粗糙,准确度下降。严格矢量衍射理论由于计算复杂,非常耗费时间和资源,因此也不是一种很有效的设计工具。 我们在本文中运用了一种简单的近似矢量衍射模型分析了几种典型衍射微光学元件衍射性能,此衍射模型采用了标量衍射理论和近似近场模型的结合。 TE和TM两种偏振模式均运用此近似矢量衍射模型进行了分析,我们发现此衍射模型可以得到比标量衍射理论更准确的结果,而与严格电磁场理论相比,它占用很少的计算时间。 相似文献
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The efficiency of conventional diffractive optical elements with échelette-type profiles drops rapidly as the illumination wavelength departs from the blaze wavelength. We use high dispersion of artificial materials to synthesize diffractive optical elements that are blazed over a broad spectral range (approximately 1 octave) or for two different wavelengths. 相似文献
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针对理论上推导轴锥镜的衍射光场分布解析式较为困难,且用菲涅耳衍射理论分析时存在近轴近似及不能适用于近场衍射光场分析的问题,采用了严格遵从标量衍射亥姆霍兹方程的角谱衍射波前重建方法,对轴锥镜在单色和准单色高斯光波照射下的横向和轴向衍射光强分布特性,以及在单色均匀平面光波照射下的轴向衍射光强分布进行了数值计算和分析。结果表明,轴锥镜后单色光衍射光强分布在几何光束重叠的菱形区域内为近似无衍射贝塞尔光强分布,轴上光强沿光轴方向呈振荡变化,轴上光强分布规律与入射光波的垂轴横向光强分布有关;入射光的准单色性使得贝塞尔衍射条纹对比度略下降、轴上光强沿光轴方向振荡程度减小,但分布规律与单色光一致。 相似文献
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紫外衍射微透镜阵列的设计与制备 总被引:1,自引:1,他引:0
为了提高紫外焦平面阵列的填充因子,可以通过微透镜阵列与紫外焦平面阵列的集成,以改善紫外焦平面阵列的探测性能。根据标量衍射理论设计了用于日盲型紫外焦平面阵列的128×128衍射微透镜阵列,其工作中心波长为350nm,单元透镜F数为F/3.56。采用组合多层镀膜与剥离的工艺方法制备了128×128衍射微透镜阵列,对具体的工艺流程和制备误差进行了分析,测量了衍射微透镜阵列的光学性能。实验结果表明:衍射微透镜阵列的衍射效率为88%,与理论值95%有偏差,制备误差主要来自对准误差和线宽误差。紫外衍射微透镜阵列具有均匀的焦斑分布,与紫外焦平面阵列单片集成能较好地改善器件的整体性能。 相似文献
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针对目前二元光学元件掩模制作工艺过程的诸多不足,对连续型平面衍射聚光透镜掩模的激光直写制作工艺进行了研究。基于基尔霍夫标量衍射理论,采用光线追迹法设计了连续型平面衍射聚光透镜掩模。采用激光直写技术,利用CLWS 300M/C极坐标激光直写设备、S1830光刻胶和MICROPOSIT 351显影液,进行了刻写实验。实验表明,激光能量、预烘烤温度、显影液浓度以及预曝光对掩模微结构的制作均有影响。最后制作了掩模。与二元光学元件掩模的制作工艺相比,该技术具有工艺简单、制作周期短且易于操作的优点。 相似文献
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We propose a method to improve the resolution of near-field optical system with a solid immersion lens by using a multiphase level Fresnel zone plate. The analyses are based on scalar angular spectrum theory. The results show that the multiphase Fresnel zone plate can not only decrease the spot size but also decrease the sidelobe intensity and enhance greatly the diffractive efficiency compared with annular amplitude filter or binary 2-, 3-, 4-zone phase filter. 相似文献
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Debashis Chanda Ladan E. Abolghasemi Peter R. Herman 《Applied Physics A: Materials Science & Processing》2008,93(1):33-37
Phase tunable multi-level diffractive optical elements define an attractive approach for single laser exposure fabrication
of 3-dimensional photonic crystal microstructures. The significant advantage of these multi-level diffractive optical elements
over two-level diffractive optical elements is the flexibility of fabricating a wide range of 3-dimensional periodic structures
by manipulating the relative phase of different diffracted beams. Here, phase tuning was applied to demonstrate fabrication
of a hybrid 3-dimensional structure intermediate between previously reported diamond-like Woodpile-type structure of tetragonal
symmetry and structure having body-centered-tetragonal lattice symmetry. Circularly polarized light was applied for the first
time to balance the diffraction order efficiencies and improve the structural uniformity. Design guidelines are presented
for generating diamond-like photonic crystal template that possesses complete photonic bandgap when inverted with high refractive
index materials. 相似文献