快速可调谐电光聚合物波导光栅

提出并设计了快速可调谐电光聚合物波导光栅.该波导光栅通过极化聚合物的线性电光效应 可实现谐振波长的纳秒级快速调谐，调谐灵敏度为61pm/V.研究了该波导光栅的反射谱和透 射谱特性与光栅周期,周期数,折射率调制函数及其调制大小的关系.讨论了波导光栅的材料 选择,制备工艺,快速可调谐性和偏振相关性.该波导光栅不仅克服了光纤光栅调谐速度慢和不利于大规模集成的不足，而且具有调谐灵敏度高,制备工艺与半导体工艺兼容和偏振无关 等优点. 关键词： 光通信器件 光波导 电光效应 聚合物 波导光栅 光纤光栅     

Diffraction efficiency increase by corona discharge in photoinduced surface-relief gratings on an azo polymer film

The diffraction efficiency of a surface-relief grating (SRG) was dramatically increased by corona discharge. We fabricated this SRG by applying surface modulation to azo polymer films, using laser interference fringes. The electric charge was deposited upon the SRG by a corona discharge in an oven. The first-order diffraction efficiency measured before and after corona discharge above the glass-transition temperature increased from ~2% to ~40% in a SRG written with a circularly polarized beam. The relief depth of the SRG as measured with an atomic-force microscope also increased, from ~130 nm to ~450 nm. The increase in diffraction efficiency was independent of the writing polarization.     

UV beam-assisted efficient formation of surface relief grating on azobenzene polymers

An efficient method is demonstrated to improve the formation of a surface relief grating (SRG) with a high amplitude. The SRG is realized by a two-beam interference technique (λ=532 nm) in an azobenzene side-chain copolymer. An UV laser beam (λ=355 nm), called assisting beam, was used to accelerate the photoisomerization process from cis-form to trans-form, resulting in a rapid cis-form ? trans-form cycle. This UV beam-assisted method allowed to increase the diffraction efficiency of the formed SRG as well as its depth. Stable gratings with modulation depth as high as 410 nm were obtained at room temperature with moderate laser power.     

Hollow-core grating fiber

We propose a new type of hollow-core fiber where the propagation is ensured by a photoinduced self-pattern acting as a surface relief grating (SRG). The SRG is written by launching a suitable laser beam with proper polarization in a capillary glass fiber with the inner surface previously coated with an azopolymer thin film. Such a grating acts as a wavelength/angle dependant reflective mirror and enhances the confinement and the propagation of the light.     

光栅制备工艺的新进展

从全息光栅法出发 ,详细阐述了应用偶氮苯聚合物光致表面调制效应制备光栅的新工艺 ,说明使用偶氮苯聚合物薄膜制备光栅方法的特点 ,介绍了采用新工艺制备的光栅的独特性质———光栅可热擦除或光学擦除 ,同时提出应用新材料光栅制造方法所面临的问题。采用新工艺实验制备了薄膜光栅     

Design and fabrication of planar blazed grating for LC rear-projection display system

Design and fabrication of planar blazed grating for single-panel LC rear-projection display system are presented. The structure of planar blazed grating is designed to disperse the incident visible light and achieve a high diffraction efficiency in a specified direction corresponding to a specified order. Two economical fabrication methods are studied. By ultrahigh-precision cutting technology, the continuous-relief planar gratings with the structure line width 0.96 and 1.5 μm are fabricated. In addition, other grating with the structure line width 2.5 μm is fabricated by using excimer laser dragging. Comparing the two fabrication results, the second one has smoother surface and smaller spacing error but the vertex angle is not enough sharp and the structure line width is limited.     

偶氮苯聚合物全息光栅衍射效率和偏振特性研究

研究了不同偏振全息模式下基于交联偶氮苯聚合物薄膜的相位光栅的形成机理、衍射效率和偏振特性.利用琼斯矢量表征了正交线偏振(SP)和半行线偏振(SS)干涉模式下的偏振干涉场.基于SP和SS两种模式,制作了无明显表成起伏的纯折射率光栅和有表面起伏的浮雕光栅.偏光显微镜(POM)观测说明纯折射率光栅具有周期性的折射率分布;近场光学显微镜(SNOM)探测说明纯折射率光栅和浮雕光栅的表而起伏在5 nm以下和 85.23 nm.实验表明.当探测光为水平偏振时,纯折射率光栅的衍射效率达到22.2%.浮雕光栅只能达到1.65%.纯折射率光栅的0、 1级衍射光分别为水平和竖直线偏振光,偏振度达到0.9969和0.9963;浮雕光栅的0, 1级衍射光均为水平线偏振光.     

Temperature and orientation dependence of surface relief gratings based on dye-doped polymer film with the interface of nematic liquid crystals

The formation of surface relief grating on dye-doped polymer film with the interface of nematic liquid crystals has been investigated by means of the holographic technique. The first-order diffraction efficiency of surface relief grating depends on the temperature and the orientation of molecular director in the interface of nematic liquid crystals. The diffraction efficiency is roughly independent of thermal fluctuations of molecular director in the most part of nematic temperature range and apparently drops near the transition temperature. The morphology of surface relief grating demonstrates that the surface modulation is larger for molecular director parallel to the groove direction. The experimental result also shows that the first-order diffraction efficiency is dependent on the surface modulation of surface relief grating.     

Electro-optical switching of liquid crystal diffraction gratings by using surface relief effect in the photopolymer

Surface relief patterns are one of the promising possibilities for the fabrication of liquid crystal (LC) electro-optical devices. Optically recorded surface relief gratings in an acrylamide based photopolymer were filled with the liquid crystal to fabricate liquid crystal diffraction gratings. E49 liquid crystals were used in this work. The switching behaviour of the diffraction grating was investigated by measuring the intensity in the first order when an electric field was applied.     

一种新颖的超结构光纤Bragg光栅梳状滤波器的设计

报道一种新颖的用于多波长光纤激光器的超结构光纤Bragg光栅（SFBG）梳状滤波器，其突出特点是仅由单个光栅构成、折射率调制和局部啁啾富于变化、反射峰均匀性好、窄带宽和标准的信道间隔.采用基于LP算法的IS光纤光栅设计技术，将整体加窗切趾法改进为各信道独立加窗切趾，成功地设计出所需的SFBG，同时对SFBG的制作技术也进行了探讨.用传输矩阵法分析反射谱、时延曲线和群时延抖动.结果表明，所设计的SFBG满足各项设计指标要求，在DWDM系统中，这种新颖的SFBG可望成为用于多波长光纤激光器的最理想的高性 能梳 关键词： 超结构光纤Bragg光栅 光栅设计 梳状滤波器     

基于多层介质膜光栅的谱合成系统光束特性分析

针对多层介质膜光栅在光束谱合成系统中的应用, 利用光线追迹方法, 建立了基于多层介质膜光栅的谱合成系统光传输模型. 多层介质膜光栅引入的相位调制包括浮雕表面上光程差与浮雕结构光程差两部分, 且受到光栅槽深、占空比和光束入射角等因素的影响. 利用衍射积分方法和光束非相干叠加原理, 计算模拟了基于多层介质膜光栅的谱合成系统的合成光束光强分布. 在此基础上, 利用强度二阶矩方法分析了合成光束的光束质量, 并讨论了多层介质膜光栅的槽深、占空比和制作误差等因素对合成光束特性的影响. 结果表明: 改变多层介质膜光栅的槽深和占空比以及中心光束入射角会影响合成光束能量, 但不会影响合成光束的光束质量, 合成光束的光束质量始终保持与单个子光束的光束质量相当; 多层介质膜光栅的制作误差对合成光束的光束质量和能量均存在明显影响.     

Artificial control of 2D ZnO patterns using interference patterning of photodynamic polymer

A facile and economic approach was demonstrated for the artificial control of the grating period in 2D ZnO nanostructures. Highly-ordered ZnO nanostructures with various periodicities (e.g., 0.5, 1.0, 1.5, and 2.0 μm) were prepared through a combination of a controlled Ar⁺ laser interference process on a PDO3 film and spin-coating technique utilizing aqueous zinc acetate/polyvinyl alcohol (PVA) solution, which obviate the need for costly and complex processes such as a chemical etching step. The grating periods of the resulting 2D ZnO arrays are well matched with those of the photodynamically manipulated 2D surface relief grating (SRG) structure of the polymeric templates. The optical properties of 2D ZnO nanostructures with various widths and spatial densities were explored.     

Experimental study of liquid-crystal alignment on a surface relief grating

In this experimental work, photofabrication of a surface relief grating (SRG) on poly[(methyl-methacrylate)-co-(DR1 methacrylate)] copolymer was used align liquid-crystal molecules in parallel. The interference pattern of circularly polarized Ar⁺ laser beams was used for this purpose, and the dynamic diffraction efficiency of the grating was measured at the same time. Then, the polymeric layers aligned by SRG were used to fabricate a homogeneous aligned liquid-crystal cell. The SRG-induced optical anisotropy of the empty cell and the cell filled with the well-known 5CB nematic liquid crystal was investigated by polarizing microscopy. In addition, the SRG-induced dichroism was studied by polarized UV-Vis spectrophotometry. Finally, the SRG-induced dichroism and optical anisotropy were compared for four different incidence angles. This alignment technique could have useful applications in in-plane switching LC displays.     

New methods of fabricating gratings for deformation measurements: A review

Gratings have been widely accepted as practical and effective deformation carriers/sensors and are commonly used in many deformation measurement methods. Since the deformation measurement sensitivity is directly proportional to the grating frequency, and the measurement accuracy is strongly affected by the grating quality. Thus, it is crucial to prepare an appropriate grating on the specimen surface that is to be measured. Over the past few decades, an increasing number of grating fabrication methods have been developed, including holographic photolithography, electron beam lithography, focused ion beam etching, nanoimprinting, soft lithography, and others. Although substantial literature regarding grating fabrication can be found, a comprehensive review is still necessary to promote the application of these methods. This review introduces the technical details and characteristics of recently developed grating fabrication methods and provides suggestions of which grating fabrication methods to use in correspondence with different deformation measurement methods. Emphasis is placed on the introduction of grating fabrication processes and the quality and applicability of the resulting gratings.     

热激法光子晶体光纤光栅制备工艺中热传导特性研究

研究了基于结构性改变的光子晶体光纤光栅的热激法制备工艺,理论分析了此种工艺的成栅原理,采用热传导理论和有限元法研究了制备过程中光子晶体光纤中的温度场分布,以及包层空气孔结构和激光参数对成栅效果的影响.研究结果表明,利用光子晶体光纤包层空气孔周期性塌缩可以形成光栅;采用两点热激法时,能够实现能量在光纤径向均匀分布,轴向近似于高斯分布;包层气孔结构加速了成栅过程,相同光斑尺寸下,光纤塌缩所需激光功率随气孔层数和气孔半径的增大而减小;最后,对包层空气孔结构为1层到7层的光子晶体光纤热激过程进行仿真,得到了空气填 关键词： 光纤光栅 光子晶体光纤 热激法 有限元法     

线偏振高斯光束通过复合型衍射光栅的传输特性

提出一种集合浮雕和折射率周期分布调制的复合型衍射光栅,并利用角谱表示和严格的模式理论研究了线偏振高斯光束通过这种复合型衍射光栅的传输特性.数值计算结果表明,在光栅的同一透射深度处复合型衍射光栅光强的起伏频率要比浮雕型光栅光强的起伏频率小.最后使用复合型衍射光栅模型,研究了亚波长体积相位全息光栅的表面起伏和入射光束的束腰宽度对衍射效率的影响. 关键词： 复合型衍射光栅 亚波长体积相位全息光栅 高斯光束 严格模式理论     

新型长周期光纤光栅的设计与研制进展

长周期光纤光栅(long-period fiber grating,LPFG)是一种宽带的透射型无源光子器件,在光纤通信和光纤传感领域应用广泛.本文从折射率空间调制的角度,根据栅格周期长短、折射率调制深度和栅面法线取向三个特征参数,对LPFG进行了分类并分析了其不足,定义了新型长周期光纤光栅(novel long-period fiber grating,NLPFG)概念并指出了其研究意义;阐述了典型的LPFG写制新技术,建立了NLPFG模型和设计理论;提出了NLPFG正、反向设计流程,阐述了NLPFG典型设计方法;综述了近年来NLPFG的研制及典型应用,展望了NLPFG研究的发展趋势.     

Spontaneous nano pattern formation under pulsed exposure: relaxation kinetics study

Formation of spontaneous surface relief grating under pulsed exposure on the surface of an azo polymer film has been investigated. We did experiments in different repetition rates and pulse widths by use an electro mechanical chopper and a diode-pumped solid-state laser with wavelength of 532?nm as pump beam. Incidence of pump beam, has been set normal to the surface of azo-polymer film. Spontaneous surface relief grating with grating pitch of ~1,250?nm was formed. For low repetition rate, relaxation due to cis-trans isomerization becomes dominant and growth rate becomes slower. A threshold for spontaneous pattern formation was found. In addition to an increase in the diffraction intensity during illumination, anomalous variation of diffraction intensity by switching on and off the laser was observed. By switching off the recording beam sharp enhancement occurred. By switching on the recording beam, after a sharp decrease in the intensity of diffracted beam, it increased further under illumination. Anomalous variations, strongly depends on polarization of the probe beam and the irradiation time for the formation of spontaneous SRG. Sharp enhancement has been attributed to cis-trans thermal isomerization and sharp decrease has been attributed to isomeration in whole surface under illumination.     

复合Ag/SiO_2正弦光栅基底SERS特性分析

当前微流控表面增强拉曼散射(SERS)检测领域常用的贵金属纳米颗粒溶胶单位体积内热点区域数量有限且热点区域范围较小,而贵金属纳米三维阵列结构加工时间长,成本高昂并存在"记忆效应"。本文提出了集成到微流道的复合Ag/SiO_2正弦光栅SERS基底结构,可以利用激光干涉光刻技术进行制备,无需预制掩膜版,可实现大面积、低成本SERS基底简易快速制备。利用严格耦合波分析方法(RCWA)建立了复合正弦光栅表面电场增强数学评估模型,推导了表面等离子体共振(SPP)耦合吸收率数学模型,分析了入射光、复合正弦光栅结构与外界环境介电常数的优化匹配关系,得到了入射光785 nm条件下的最佳复合正弦光栅结构。通过制备加工并实验验证了复合正弦光栅的SERS性能,SERS增强因子(EF)能够达到10~4。     

等离子体光栅靶的表面粗糙度对高次谐波产生的影响

极紫外光和软X射线由于其波长和脉冲持续时间极短,可用于超快物理过程和物质微观结构的探测.最近几年,研究人员发现激光和等离子体相互作用可以产生持续时间极短(阿秒)且相干性较好的高次谐波辐射,其波长可接近甚至达到水窗波段.然而,实验研究指出,理论上应出现的一些谐波在实验中并没有出现.本文针对超短超强激光与非理想条件下的等离子体光栅靶相互作用产生高次谐波的物理过程进行了理论分析和粒子模拟.研究结果表明,等离子体光栅的周期性结构对于高次谐波的频谱和辐射角分布存在显著调制效果.光栅靶表面粗糙度直接影响光栅的光学调制效果,改变高次谐波的频谱分布和辐射角分布.理想光栅条件下,满足光栅匹配条件的特定阶数谐波明显获得增强,且辐射张角集中在平行靶面的方向.靶表面粗糙度的出现,导致光栅匹配条件失效,高次谐波能量向各阶分散且辐射张角逐渐偏离靶表面方向.研究结果较好地解释了实验中观测到的谐波频谱分布,为进一步的研究提供了一定参考.