扫描积分塔尔博特光刻条纹质量影响因素模拟分析

基于角谱衍射理论,对扫描积分塔尔博特光刻术进行了理论分析与数值模拟。研究了扫描距离、扫描起始位置、扫描速度非匀速以及照明光源不同特性对扫描积分塔尔博特光刻所得光栅条纹质量的影响。模拟结果表明,当扫描距离为塔尔博特周期的整数倍时,扫描起始位置、扫描速度的非匀速性对扫描积分塔尔博特光刻的成像质量影响较小;当入射光源存在一定谱宽或发散角不大于0.05°时,扫描积分塔尔博特光刻仍可得到对比度较一致的倍频光栅条纹,证实了扫描积分塔尔博特光刻具有良好的工艺适用性。扫描积分塔尔博特光刻不需要昂贵而复杂的投影光学系统,可克服塔尔博特自成像有限焦深问题,对掩模与基片的定位精度及涂胶基片的平整度容忍度较高。该方法具有在非平面基底上制备大面积、低成本、高精度周期微纳结构的应用前景。     

分析光栅分数塔尔博特效应的一组新方程

对一维开口比为1/M(这里M为大于1的正整数)的短形光栅,建立了一组新 在分数塔尔博特(Talbot)距离上计算其菲涅 法射光场分布的简单方程.在该方程中考虑了光栅结构与分数塔尔博特距离的联系,显然比迭代方程和基于距离的方程更方便地描述分数塔尔博特效应.给出了一种研究光栅分数塔尔博特铲应的新途径.     

任意发光类型的多色光照明下光栅塔尔博特效应的研究

利用部分相干光理论对多色光源照明下光栅的菲涅耳衍射进行了理论分析,得到了适用于任意发光类型(脉冲或连续发光)的多色光源的衍射光强的一般公式,理论结果表明菲涅耳衍射区的平均衍射光强的形式只与光源的频谱分布有关,这对借助于连续发光光源来研究脉冲光源照明下光栅的塔尔博特效应以及用来确定脉冲光源的性能参量提供了有力的参考依据。此外,详细讨论了光源的频谱分布对光栅塔尔博特效应的影响并进行了相应的数值计算。实验中通过选用不同频率的激光分别照明光栅,拍摄到对应于不同频率的衍射光强分布图像,从而间接获得多色光同时照明光栅时总的衍射光强分布。实验结果表明,理论和实验符合较好。     

光栅在超短脉冲激光照射下的塔尔博特效应

首先导出了光栅在短脉冲激光照射下的菲涅耳衍射光场的方程 ,利用该方程分析了一个开口比为 1∶4的光栅的衍射光场。数值计算结果表明当激光脉冲的半极大值全宽 (FWHM)Δτ在皮秒数量级时 ,可以得到塔尔博特自成像。当激光脉冲的 Δτ从皮秒逐渐减小时 ,塔尔博特自成像现象逐渐消失。而当激光脉冲的Δτ小于几十个飞秒时在第一个塔尔博特距离处光栅的衍射光强的最大值随Δτ的减小而减小     

部分相干光照明下光栅的塔尔博特效应

首先利用部分相干光理论详细地分析了在部分相干光照明下光栅的菲涅耳衍射,给出了观察面上衍射光强分布的一般公式,并就光源的发光面积对光栅塔尔博特效应的影响进行了讨论,得到了光栅衍射光强的分布随着照明光源的发光尺寸的增加而逐渐变得平滑这一结论．并且,当光源发光尺寸增加到毫米量级时,光栅的塔尔博特效应将完全消失。在实验上埘不同发光尺寸的扩展作相干光源照明光栅时的菲涅耳衍射光强进行了测量,实验结果与理论分析得出的结论相符合。     

基于波长扫描塔尔博特效应的阶高测量理论研究

近年来,多维阶高测量问题倍受关注,两波长或波长扫描方式的塔尔博特效应被应用于多维阶高测量.研究表明,基于塔尔博特(Talbot)效应的阶高测量方法具有仪器结构紧凑、无需机械扫描、稳定性高和测量范围大等优点.因没有光栅或检测器件的任何机械移动,可避免由此导致的相位问题及测量误差.取代相位信息,该方法采用衍射条纹的最大衬比度来判定塔尔博特像,测试中均采用占空比为1:2的龙基(Ronchi)光栅作为周期结构衍射物,利用不同波长塔尔博特像的像距来确定物体阶高.因为测量的是条纹衬比度而非绝对强度,所以阶高测量精度依赖于条纹衬比度,最大衬比度的获取与判定是非常重要的.在分析对比的基础上指出,采用非龙基型光栅,如正弦振幅光栅或相位光栅,能使成像条纹分布更合理,有效地提高成像条纹的衬比度.研究还表明,所采用周期结构衍射物的空间周期越小,分辨率就越高,从而给出了分辨率同衍射物空间周期的定量关系.     

多芯光纤激光器的超模及模式选择问题研究

根据耦合模理论,分析了多芯光纤支持的超模,推导了超模场分布函数的解析表达式,并利用柯林斯(Collins)公式计算这些超模光束的二阶矩,分析各超模的光束质量。为了获得较好质量的光束输出,还对利用塔尔博特腔进行多芯光纤激光器的模式选择进行了数值分析。计算结果表明,只要选择合适的距离参量,塔尔博特腔可以有效地进行模式选择。     

部分相干同步辐射照射下光栅分数塔尔博特效应

基于高斯谢尔光束的相干模式分解理论和波动光学,建立了部分相干同步辐射硬X射线光束通过光学器件的传播模型。模拟了微聚焦X射线光束照射下光栅的分数塔尔博特效应,得到了聚焦光束的光强分布和相干特性变化,并分析了散焦光束入射下的光栅自成像。然后通过模拟准直光束入射下的光栅塔尔博特效应,得到了不同传播距离处自成像条纹的变化情况,分析了影响光栅自成像条纹形状的因素。通过光栅衍射条纹测量同步辐射相干度,发现对矩形相位光栅来说,应该对衍射图样进行傅里叶分解,求出各级傅里叶系数随传播距离的变化曲线,从而得到入射光束相干特性。     

应用光纤分数塔尔博特效应产生重复频率倍频的光脉冲序列

提出了一种基于光纤分数塔尔博特(Talbot)效应的光脉冲序列的倍频方法,介绍了Talbot效应的基本原理;应用自制的可调色散补偿器,将光纤锁模激光器产生的重复频率为10 GHz、脉宽约2.8 ps的窄脉冲序列倍频到重复频率为20,40和50 GHz的脉冲序列,也将重复频率5 GHz的窄脉冲序列经8倍频变换得到40 GHz的脉冲序列;通过分析窄脉冲序列的频谱,指出了实验中倍频得到的40 GHz和50 GHz脉冲质量下降的原因,提出了相应的优化措施。     

中能X射线光栅相衬显微成像分析及模拟

理论分析了基于相位光栅分数塔尔博特效应的X射线相衬显微成像原理,采用菲涅耳衍射公式推导出相位光栅在两个不同距离处的成像结果公式.然后建立一个水合蛋白质细胞模型,对成像系统进行了参数设计,得出1～2 keY的中能波段X射线是兼顾大景深和高成像衬度的最优选择.针对10μm厚的细胞模型,选取1.5 keY的中能X射线做模拟计...     

Variable Wavelengths Fiber Bragg Gratings Written with A Phase Mask and Four Prisms

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Variable Wavelengths Fiber Bragg Gratings Written with A Phase Mask and Four Prisms

Using only one diffractive element, the Talbot interferometer provides a robust and inherently stable method for reproducing fiber Bragg gratings with variable wavelengths, and reduces the complexity of the fiber grating fabrication system. However, the usable length of the grating is limited by the practical length of the mirrors. This paper presents a phase mask with two fixed prisms and two rotational prisms to inscribe fiber Bragg gratings with variable Bragg wavelengths. In this system, the fiber Bragg grating is inscribed by UV interference stripes of 193 nm derived from two rotational prisms and two fixed prisms, where phase mask is used as a beam splitter of ±1 order diffraction light. It is noteworthy that the tunable phase mask interferometer decreases the demand of the length of prism evidently.     

基于泰伯效应的高斯光束尺寸测量

光栅用在高斯光束参数测量中的突出优点是方法简单，成本较低，全息光栅由于其制备容易，无周期误差而比一般光栅具有更多的优点。在用光栅进行光斑测量的实验中，观察到由全息光栅引起的泰伯（Ｔａｌｂｏｔ）效应携带有关光斑参数的有用信息，本文提出了一种基于泰伯效应的测量方法，只需测定条纹间隔就能确定高斯光束尺寸，因此降低了对光源或光栅定位精度，电路和光源稳定性的要求，文中聚焦高斯光束照明全息光栅时光场分布，及其     

Changing photo-written Bragg wavelengths of fiber gratings via one phase mask and four mirrors

A phase mask interferometer is developed to photo-write long gratings with arbitrary Bragg wavelengths. In this system, the fiber Bragg grating is photo-written by UV interference stripes of 193 nm reflected from two rotatable mirrors and two fixed mirrors, where the phase mask is not only used as a beam splitter, but also initialized the reference quantity of Bragg wavelength; the fixed mirrors are used for reducing the incident angle; the rotatable mirrors are used for adjusting the corresponding photo-written Bragg wavelength. It is worth noting that the photo-written length is fourfold as high as the length in the Talbot interferometer with the same mirror size.     

改变写入Bragg波长的干涉条纹运动的扫描式Talbot干涉仪

一种干涉条纹运动的扫描式Talbot干涉仪被用于改变光纤Bragg光栅的写入Bragg波长。在系统中,光纤光栅是由来自相位掩模的±1级衍射光经平面镜反射后在远场形成紫外干涉条纹写入的,其中,相位掩模被用作±1级衍射光的分束器。值得注意的是通过干涉条纹的运动来扫描写入光纤光栅,有效降低了Talbot干涉仪对写入光源相干性的要求。     

Collimation method using fourier imaging and moire techniques

Two techniques are proposed for beam collimation with the Talbot interferometer. One is called the mismatch method in which two gratings with slightly different periods are used. In the other method (called the grating shift method), one of two gratings of the same period is shifted in its plane in the direction perpendicular to the grating lines.     

畴腐蚀掺镁铌酸锂可调阵列光分束器的研究

研究了不同畴腐蚀深度的掺镁铌酸锂二维六角可调阵列光分束器的分数Talbot效应.对不同Talbot分数β和不同畴腐蚀深度的阵列光分束器Talbot衍射像进行了数值模拟理论研究.模拟结果表明,Talbot分数β可以改变Talbot衍射像的周期及结构分布,而畴腐蚀深度可有效调制衍射像的光强分布.在理论研究的基础上,设计并制备了具有不同畴腐蚀深度的掺镁铌酸锂二维六角阵列光分束器,对其在不同Talbot分数β条件下的分数Talbot效应进行了通光实验研究,实现了畴腐蚀阵列光分束器对近场Talbot衍射光强分布的调制,实验结果与理论研究结果一致.     

Quasi-Talbot effect of the sub-wavelength Ag grating

When a TM-polarized beam incidents normally on a thick sub-wavelength Ag grating with small opening ratio, self-images form in the transparent dielectric layer due to contributions not only from waves radiating from the slits, but also from the Surface Plasmons (SPs) created on Ag surface. These two contributions make the self-images connect together along the propagation direction and form continuous stripes with period equal to half of that of the grating. We define this phenomenon as quasi-Talbot effect. For a thin sub-wavelength Ag grating or a grating with large opening ratio, its intensity distribution conforms to the conventional Talbot effect. Investigation on quasi-Talbot effect of sub-wavelength metal grating can develop new applications in nano-scale devices.     

Symmetric Talbot bands experiment

By impinging a step phase-shifted white light beam on a grating-based interferometer, one of diffraction orders is modulated and interference bands so-called “Talbot bands” are formed. Here, classical Talbot bands set up is generalized to the symmetry configuration, in which two glass plates of the same thickness instead of one plate, are inserted halfway into the grating interferometer aperture. Formation of Talbot bands were studied theoretically and experimentally. Frequency impulse response of the new Talbot bands setup was, also presented. It was demonstrated that symmetric set-up causes modulation of both of two opposite orders, according to the theory. In this manner, their visibility is the same. As a result, this similarity of the visibility is reduced while the symmetric arrangement of the glass plates with respect to the optical axis, is broken.     

The effect of arbitrary small discrepancy between normal directions of grating planes in Talbot interferometry

The effect of nonparallel grating planes in Talbot interferometry is discussed when an arbitrary relative inclination exists between the normal directions of the two grating planes. The inclination can be composed of the two angles, and β, which are generated by rotating the beam splitter grating about the two axes parallel to and perpendicular to the line direction of the grating. Theoretical analyses indicate that the tilt angle of the moiré fringes is very sensitive to but not to β. Experimental results coincide well with the theoretical analyses. Methods of judging and removing the two small angles are briefly discussed.