偏振组合对光子晶体全息制作影响的数值模拟及实验研究

光子晶体是类比固体晶格制作的新型人工材料,激光全息法是制作光子晶体的重要方法之一,光束偏振在其中起到关键作用。从多光束干涉原理出发,以斜方光子晶体为例探讨了其全息制作的设计思路及光束构型。进而结合计算机模拟,系统研究了线偏振、圆偏振、椭圆偏振等不同偏振组合对"原子"的影响,发现偏振组合和光强比对"原子"形状、取向和位置存在显著影响。进一步设计实验进行验证,结合计算机实时监控调节各光束的偏振和光强,获得了不同偏振组合和光强比下的多种光子晶体结构,发现实验结果与理论预测、数值模拟均符合得很好。该研究不仅有助于提高特定"原子"光子晶体的设计效率,而且可有效降低偏振操控的盲目性,提高实验效率。     

全息干涉光学格点一到三维空间维度的简捷变换

采用计算机模拟技术,研究了激光全息干涉光学格点从一维、二维到三维的简易空间变换.采用镜像添加光束技术,改变光束配置,可以较容易地实现干涉场光学格点从二维到三维的空间变换.进一步研究发现,若改变入射光束的偏振方向,干涉场可由三维结构变为一维层状结构,并且层状结构周期最小可达半个光波长.本文对全息光刻制作各种空间维度,尤其是光学波段禁带的光子晶体提供了简捷可行的实验技术思路.     

计算机模拟偏振对激光全息的影响

通过计算机对多束激光相干产生的空间干涉光场进行模拟,归纳出光束偏振态改变时,激光相干产生光学晶格效果的变化规律,提供了激光全息技术中激光束偏振态的最佳组合,使激光全息技术制作理想的亚微米单晶结构更方便快捷.还通过实验验证了理论模拟结果,实验结果与计算机模拟结果完全一致 关键词： 激光全息技术 偏振态 光学晶格 光子晶体     

偏振纠缠光子对产生中的相位补偿

我们通过腔增强自发参量下转换方法产生了795nm窄带偏振关联光子对,利用波片组合对两个不同偏振光子之间的相位差进行了补偿,通过单光子符合计数后选择获得了偏振纠缠光子对。对两路输出光子进行D(+45°偏振)或A(-45°偏振)偏振投影,分别在DD和DA偏振基下测量了干涉对比度V=|NDD-NDA/NDD+NDA|随补偿半波片的角度变化,干涉对比度在补偿角为10°时达到最大92%。在补偿角度为10°时,测量得到纠缠光子对S值为2.6±0.07,违背Bell-CHSH不等式8.57个标准差。     

用双光束干涉制作二维光子晶体

利用双光束干涉,在光敏材料上制作光子晶体结构.通过改变两束光之间的夹角可以改变制备样品的周期.改变曝光次数以及两次曝光时干涉条纹的夹角可以分别得到一维、二维正方晶格以及二维三角晶格结构的光子晶体.     

表面等离激元体干涉制备纳米光子晶体的模拟分析

利用表面等离激元短波长和近场增强效应的特性,用多束P偏振态相干光激发表面等离激元(SPPs),并优化干涉光刻的曝光参数,可获得高分辨率、高对比度周期性纳米结构.阐述了多束SPPs干涉法制备纳米光子晶体的原理,并得到了干涉场强度分布随光束增加的关系.随着干涉SPPs数目的增加,干涉场会复杂变化,对此进行了计算机模拟.模拟了三束SPPs和六束SPPs干涉的强度分布,并分析了调制技术干涉曝光结果,该方法适合光电子器件中大范围亚波长的周期性孔阵或点阵结构的制作以及纳米量级光子晶体的的制作,并可以有效降低制作成本.     

三光束飞秒激光干涉在GaP,ZnSe表面诱导二维复合纳米-微米周期结构

报道了三光束飞秒激光干涉在GaP和ZnSe晶体表面诱导二维复合纳米-微米周期结构.改变三束光的偏振组合方式,可以得到不同的纳米-微米复合结构.理论计算了相应偏振条件下光场强度分布、椭偏度分布和偏振方向分布.实验和理论计算结果表明,烧蚀斑上的微米长周期结构是由三光束干涉的强度花样决定,短周期纳米结构是由光场的偏振干涉花样决定.这些研究在纳米材料制备、超高密度光存储以及材料特性周期性调制等方面有很大的应用前景.     

偏振态对三光束激光干涉分布的影响

多光束激光干涉技术已经广泛地应用到制作大面积的周期性结构。制作材料也从无机材料扩展到了有机材料。根据多光束干涉理论,模拟三光束激光发生干涉后的强度分布;在不改变入射角的条件下,仅通过调整偏振态组合得到二维"蜂窝"型(S-S-S,P-P-P)和"介质柱"型(C-C-C)周期性结构。同时,由于有机材料对于光偏振态的响应性质,对于干涉后偏振态的分布情况也进行了分析,发现在一个维格纳-赛兹(Wigner-Seitz)原胞中,线偏振组合干涉后得到的偏振态不是线偏振,而是出现线偏振到椭圆偏振再到圆偏振的变化。     

静态偏振风成像干涉仪光传输特性和光通量改善

静态偏振风成像干涉仪利用偏振光束来获得干涉图, 光束在偏振元件中的传输特性成为分析研究的关键. Jones矩阵用于分析系统的光学传输特性和偏振态变化过程, 形式简洁,计算方便,容易得出光学元件对系统性能的影响.本文用Jones矩阵对静态偏振风成像干涉仪系统进行了描述, 推导出了适用于普遍情况的系统矩阵表达式,计算出核心偏振元件的偏振化方向和波片方位角对应于系统光通量和干涉调制度的关系,确定了系统中各偏振元件的最佳偏振化方向和波片的最佳方位角; 并通过视场展宽技术和提高四面角锥棱镜的透光率对光通量加以改善,利用光线追迹软件仿真, 对视场展宽前后的干涉强度作了对比,达到预期的效果.为静态偏振干涉成像光谱仪的设计、 研制和工程化提供重要理论和实践指导.     

Archimedes 32,4,3,4结构光子晶体中与偏振无关的自准直分束器

通过等频图分析并结合时域有限差分法法模拟, 在Archimedes 3²,4,3,4结构排列的二维光子晶体中同一频率下同时实现了电磁波两种偏振态的自准直. 研究发现,在该结构光子晶体中引入缺陷,当线缺陷宽度改变时, TE和TM两种偏振态光束的分束效果将会随之变化.由此通过控制缺陷宽度,分别实现了两种偏振态光束的50% ∶50%分束以及90°大角度光折弯,分束和折弯的效率都较为理想,为未来设计基于光子晶体的新型光子学器件提供了一种新的思路.     

激光全息光刻技术在微纳光子结构制备中的应用进展

微纳光子结构研究随着光子学、半导体物理学及微加工技术的发展而逐渐蓬勃开展,并在其结构、理论、制备技术等方面取得了系列进展。受限于目前的微加工技术水平,要成功制备大尺度、高质量的光子材料仍然存在着一定挑战。激光全息光刻技术作为一种简便快捷的微结构制作技术已经发展成为一种经济快速制作大面积微纳超材料及光子晶体模板的重要手段。介绍了激光全息光刻技术的原理,详细阐述了该技术在制作三维面心立方、木堆积结构、金刚石结构光子晶体以及光学周期类准晶、手性超材料、周期性缺陷结构等微纳光子结构中的应用研究进展。激光全息光刻技术成功制作微纳光子结构为光子材料在更多领域的广泛应用提供了基础和方法。     

激光全息法制作二、三维光子晶体的模拟计算及禁带分析

激光全息法制作二、三维光子晶体相比于传统半导体微加工及精密机械加工技术具有很多优势，比如通过一次光辐射就可以制作出大体积、均匀的周期性结构，且能更自由、更容易地控制光子晶体结构.提出一种多光束干涉模型，通过设计模型中光束的各项参数，计算分析出二、三维光子晶体的结构.基于平面波展开法，理论计算了fcc结构光子晶体的完全禁带随填充率和介电常数比变化的情况.以上计算结果为后期实验中采用激光全息法制作二、三维光子晶体结构提供了良好的指导方向和理论依据. 关键词： 光子晶体 激光全息 多光束干涉 完全禁带     

Fabrication of large-area 3D photonic crystals using a holographic optical element

A holographic technique for fabricating 3D photonic crystal is presented. The key element in the fabrication system is a holographic optical element (HOE) consisting of three gratings. Used in combination with a mask, the HOE can generate four beams under single illuminating beam, and 3D lattice structures can be formed by the interference of the four beams. Holographic approach is used to make HOE, so large area lattice structures can be fabricated. Numerical simulations indicate that beam intensity ratio of central beam to outer beam is one of the factors that affects the structures fabricated in photoresist, and high diffraction efficiency of the gratings in HOE is favorable when using cw laser with relatively low power as light source. Experimental results show clear 3D lattice structures fabricated using the HOE, verifying the effectiveness of the technique.     

Holographic lithography of a two-dimensional hexagonal structure: Effect of beam polarization

A comparison is made between the theoretical determination of the interference contrast function with fabricated two-dimensional hexagonal structures of submicron lattice constant. Experiments were performed using a siloxane based hybrid organic-inorganic material and a holographic lithography method.Thin hybrid structured layers were fabricated and characterized for different conditions of beam polarizations between 0° and 90°. As a result, the photo patterning appears to be strongly dependent on beam polarization in accordance with theoretical predictions.     

The three-dimensional photonic crystals coated by gold nanoparticles

We report on the fabrication of metallodielectric photonic crystals by means of interference lithography and subsequent coating by gold nanoparticles. The grating is realized in a SU-8 photoresist using a He-Cd laser of wavelength 442 nm. The use of the wavelength found within the photoresist low absorption band enables fabricating structures that are uniform in depth. Parameters of the photoresist exposure and development for obtaining a porous structure corresponding to an orthorhombic lattice are determined. Coating of photonic crystals by gold nanoparticles is realized by reduction of chloroauric acid by a number of reductants in a water solution. This research shows that the combination of interference lithography and chemical coating by metal is attractive for the fabrication of metallodielectric three-dimensionally periodic microstructures.     

Two modes of laser lithography fabrication of three-dimensional submicrometer structures

The modes of laser lithography fabrication of three-dimensional submicrometer structures have been studied. The method is based on the effect of threshold two-photon polymerization of a photosensitive material at the laser beam focus. To determine the lithograph workspace in the coordinates “laser power-speed of the sample displacement with respect to the laser focus,” a series of photonic crystals with the woodpile structure is prepared. Two methods for fabricating three-dimensional structures, i.e., raster scanning and vector graphics (or the vector method) are analyzed in detail. The advantages of the vector method for fabricating periodic structures are demonstrated using crystals of inverted yablonovite as an example. The prepared samples are studied by scanning electron microscopy.     

多光束激光干涉光刻图样

利用电磁理论,研究了多光束激光干涉图样的产生原理,结合计算机数值模拟和相关实验结果,分析了干涉图样的影响因素.研究结果表明:多光束激光干涉图样可以看成是多组余弦分布的平行线条纹的叠加;相干光束的偏振方向、入射方向、光束间相位差是干涉图样的重要影响因素,改变这些因素,余弦分布的平行线条纹的振幅、位置、周期和方向发生变化,...     

Optics design of a top-cut prism interferometer for holographic photonic quasicrystals

Optical interference holography has been proved to be a useful technique in fabricating periodic photonic crystals in which electromagnetic waves are forbidden in certain frequency band-gaps. Compared to periodic crystals, quasicrystals have higher point group symmetry and are more favorable in achieving complete band-gaps. In this report, a top-cut prism interferometer is designed and optimized for photonic quasicrystals. By changing the prism parameters and characteristics of different beams, different quasicrystalline structures can be obtained. At the same time, the diffraction patterns of the designed structures are also provided and reveal the ten-fold symmetry of the structures more clearly. Furthermore, the effect of the intensity threshold on the quasicrystalline structures is also investigated. This will provide guidance for the large-area and fast production of ten-fold quasicrystalline structures with high quality.     

Polarization-independent self-collimating bends and beam splitters in photonic crystals

Polarization independent bends and beam splitters for transverse electric (TE) and transverse magnetic (TM) polarizations have been demonstrated in two-dimensional (2D) photonic crystals (PhCs). In virtuel of equi-frequency contour analysis and finite-difference time-domain calculations, self-collimation behaviors for TE- and TM-polarizations are achieved at the same frequency. Simulation results show a 90-degree bend with 90% efficiency and beam splitters with about 96% total efficiency for both TE- and TMpolarizations, where the light is self-guided by the self-collimation effect. Such bends and beam splitters are expected to play important roles in optical devices where polarization insensitivity is needed.     

Color dispersion in two-dimensional phase array based on polymer-dispersed liquid crystal film

This work proposes a feasible method for fabricating a two-dimensional periodic structure with a sub-micrometer periodicity using a single laser beam, based on polymer-dispersed liquid crystal (PDLC) films. The resulting nano-PDLC morphology is highly symmetrical, and similar to that written using multi-beam interference. The increase in the electric-tunability of the optical behavior, including spatial diffraction and color dispersion, is examined. The color dispersion provides optical evidence of the periodic structure of the PDLC film.