利用一块相位掩模和两块棱镜改变光纤光栅的写入Bragg波长

一种相位掩模干涉仪被用于写入不同的Bragg波长的。在该系统中,光纤光栅是由来自两可旋转棱镜所形成的紫外干涉条纹写入的,其中,相位掩模被用作&;#61617;1级衍射光的分束器。并且,当两块顶角由相位掩模的&;#61617;1级衍射角和棱镜折射率确定的棱镜的底部相互平行放置时,该相位掩模给出了Bragg波长的参考值。当Bragg波长的移位为1 nm时,棱镜最大的旋转角为1 degree,最小的旋转角是~2.4 minute。与Talbot干涉仪中平面镜的旋转角~23 second/nm相比,该相位干涉仪中棱镜的旋转精度降低了2~3个数量级。替代了许多具有不同光栅周期的相位掩模,该可调谐相位掩模干涉仪仅用一块相位掩模和两块旋转棱镜就实现了写入具有不同Bragg波长的光栅。     

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.     

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

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双棱镜改变写入Bragg波长的相位掩模技术

将一种可旋转的双棱镜引入到相位掩模技术中以改变光栅的写入Bragg波长.在该系统中,光纤光栅是由来自可旋转双棱镜所形成的波长为248 nm的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,通过双棱镜的旋转可改变两写入光束的交叉角.为了初始化Bragg波长的参考值,双光栅的顶角由相位掩模的 1级衍射角和双棱镜的折射率确定.因为在～100 nm范围内两光束的非对称旋转对光栅周期的改变是5×10~(-4) nm,双棱镜引入的光栅的闪耀可忽略.当Bragg波长的移位为1 nm时,棱镜最大的旋转角为～1 degree,最小的旋转角是～2.4 min.与Talbot干涉仪中平面镜的旋转角～23 s/nm相比,该相位干涉仪中棱镜的旋转精度降低了2～3个数量级.     

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。     

楔块调整式Talbot干涉仪改变写入Bragg波长的调谐误差

在楔块调整式Talbot干涉仪中,光纤Bragg光栅的写入区为直接由相位模板衍射的±1级衍射光束形成的干涉条纹的近场干涉区,和由±1级衍射光束经两平面镜反射后形成的可调谐写入Bragg波长的干涉条纹的远场干涉区。在改变写入光纤光栅Bragg波长的过程中,光纤光栅的Bragg波长是由平面镜的交叉角决定的,而且,影响调谐精度的三种主要因素被控制在光纤光栅生产允许的范围内,即推动机构的位移误差系数Cd为～-0.08nm/μm,楔块的倾斜误差系数Cα为-0.15～0.23nm/(′),和转动机构的传动角误差系数Cβ为～-0.08nm/(′)。     

双波长啁啾相移光纤光栅

理论研究并实验验证了一种含有两段π相移的啁啾相移光纤光栅.采用F矩阵对啁啾相移光纤光栅进行计算并分析了该光栅的谱特性.含有两段π相移的啁啾相移光纤光栅可以在普通啁啾光栅透射谱阻带中产生双波长透射峰,透射峰位置直接取决于光栅中π相移的位置,透射峰的线宽和透射峰的波长间隔没有关系,仅随着啁啾率的增大而增大.采用带相位掩模的逐点扫描法对含有两段π相移的双波长啁啾相移光栅进行了制作,获得波长间隔为8 nm的双波长透射谱的光栅器件.该光栅的消光比和3 dB谱线宽分别为20 dB和0.08 nm,实验结果和理论设计一致.     

Fabrication of Dual-Wavelength Fiber Bragg Grating with a Longitudinal Stretch

A method of fabricating dual-wavelength fiber Bragg grating with a uniform phase mask is demonstrated. Theoretical analysis and numerical simulation using Matrix method are given. The moving exposing technique is adopted. Good control over the grating’s reflectivity and the separation of the two Bragg wavelengths is enabled by adjusting the stretch, the length of the grating, and the exposure. A grating with two equal transmission peaks of 19.5 dB is obtained by using this method, and the separation of the two Bragg wavelengths is 0.78 nm. Translated from Chinese Journal of Quantum Electronics, 2005, 22(1) (in Chinese)     

Dispersion error of a beam splitter cube in white-light spectral interferometry

We revealed that the phase function of a thin-film structure measured by a white-light spectral interferometric technique depends on the path length difference adjusted in a Michelson interferometer. This phenomenon is due to a dispersion error of a beam splitter cube, the effective thickness of which varies with the adjusted path length difference. A technique for eliminating the effect in measurement of the phase function is described. In a first step, the Michelson interferometer with same metallic mirrors is used to measure the effective thickness of the beam splitter cube as a function of the path length difference. In a second step, one of the mirrors of the interferometer is replaced by a thin-film structure and its phase function is measured for the same path length differences as those adjusted in the first step. In both steps, the phase is retrieved from the recorded spectral interferograms by using a windowed Fourier transform applied in the wavelength domain.     

用紫外光直接在光纤内写入布拉格反射光栅的实验研究

用紫外光直接在光纤内写入布拉格反射光栅的实验研究杜卫冲谭华耀＊刘颂豪华南师范大学，激光生命科学研究所，广州５１０６３１＊香港理工大学，电机系自１９８９年Ｍｅｌｔａｚ［１］首次提出采用两束波长位于掺Ｇｅ－石英光纤吸收带内的相干紫外激光相干涉，从侧面照射...     

Analysis on the laser beam pointing instability induced fringe shift and contrast dilution from different interferometers used for writing fiber Bragg grating

This paper presents an analysis on the effect of laser beam pointing instability on the fringe shift and hence the contrast dilution of superposed fringes from two beam interferometers. The interferometers analyzed are those commonly used in writing fiber Bragg grating (FBG) such as phase mask, bi-prism and phase mask based Talbot/Holographic type. The beam pointing instability is incorporated as slight change in the angle between two interfering beams. The relative immunity of different interferometers to laser beam pointing is discussed vs location of FBG writing plane from the beam splitter. The effect of the beam pointing was minimum in proximity FBG writing by phase mask. The effect, in terms of fringes contrast dilution, was worst in case of large length interferometers e.g. phase mask based-Talbot interferometer. For intermediate length prism interferometers, the effect was moderate. For a given length interferometer, the fringe shift was directly proportional to beam pointing angle and inversely proportional to fringe separation. Theoretical analysis is verified experimentally by studying the fringe instability of interference pattern formed by a bi-prism of angle 2^o with the copper vapour laser (CVL, λ = 510 nm) beams of different beam pointing instabilities.     

相移光纤光栅的制作和特性

在光纤光栅的刻蚀平台中引入精密移动电机,控制相位掩模板的移动,从而在光纤光栅的刻蚀过程中,在光栅的固定位置引入相移量,采用此简单易行的方法制作出了多种相移光纤光栅,分析所刻光纤光栅的光谱曲线,符合理论分析和设计的要求。     

基于光纤Bragg光栅位移测量的研究

介绍了一种基于布喇格光纤光栅技术的位移测量方法。利用宽带光源经不同的布喇格光栅得到一种由温度稳定器控制波长稳定性的合成光源。由于系统设计的合成光源波长比常规光源的波长长，所以允许的光程差测量范崮提高了几百倍，从而使得布喇格光纤光栅的波长准确性提高了干涉仪位移测量的准确性。此外，利用光外差法马赫一曾德尔干涉仪进行了位移测量实验，得到了很好的效果。     

Apodised fiber Bragg gratings fabricated with a uniform phase mask using Gaussian beam laser

A new exposure scheme for fabricating apodised fiber Bragg gratings by the use of a uniform phase mask and a Gaussian beam laser is demonstrated. Average refractive index is kept nearly constant along the grating to derive a side lobe suppression of 20 dB in the shorter wavelength. This scheme allows the writing of truly apodized fiber Bragg gratings.     

用3×3耦合器的干涉仪直接解调光纤光栅传感器的信号

为了简单直接地解调出光纤光栅的波长移动 ,提出了另外一种非平衡马赫曾德尔干涉仪的直接解调技术。用一只 2× 2耦合器和一只 3× 3耦合器组成非平衡的马赫曾德尔光纤干涉仪 ,作为光纤光栅的波长移动解调器。解调器输出的 3路信号 ,互成 12 0°相位差。通过对 3路输出信号计算的方法 ,就可以直接解调出光纤光栅的波长移动。将 3路信号采集送入计算机 ,用软件实现了信号的解调。测量结果表明 ,在干涉仪两臂长度相关 5mm时 ,测量动态应变的分辨率达到了 0 5 1nε/Hz1/2 。还得到了输出信号的频谱和输入输出信号的关系。     

用于制作光纤光栅的Talbot干涉仪的分析与建模

对用于制作光纤光栅的Talbot干涉仪进行了分析.当考虑准分子激光器的空间相干性和时间相干性时,几何光学中的光线法并不能给出Talbot干涉仪干涉场的真实强度分布情况,而通过光的电磁理论,则可以提供对干涉场的详细描述.基于电磁理论,建立了一个Talbot干涉仪干涉场计算模型,并首次将Talbot干涉仪的反射镜转角作为模型计算参数加以考虑,随后进行了一系列的计算.计算结果显示了干涉场的分布,同时表明空间相干性对Talbot干涉仪的近场干涉和远场干涉影响都很大,其中远场干涉对空间相干性的要求更严格,且对于远场干涉,反射镜转角的影响不可忽视.     

非线性二次曝光法制作三角形光纤Bragg光栅

提出了一种利用非线性二次曝光技术制作三角形光纤Bragg光栅的新方法.该方法只使用普通Bragg位相模板,采用两次曝光技术,通过控制光纤光栅的本地谐振波长和反射率,达到控制光纤光栅谱形的目的.第一次直接对光纤曝光,用来控制光纤光栅谐振波长;第二次通过位相模板曝光,用来控制光纤光栅的反射率.考虑到光敏光纤感光特性曲线的多项e负指数变化规律,按照"分步写入光纤光栅设计软件"进行曝光分布设计,利用"分步曝光光纤光栅写入系统"进行曝光控制,使用信息产业部第46研究所生产的DCS-01型光敏光纤,得到了线性范围1.24 nm、反射率为0～64%的三角形光纤Bragg光栅.三角形光纤Bragg光栅作为光纤光栅传感解调器件,在光纤传感领域具有重要应用价值.     

光致折变布拉格光栅实验研究

本文介绍了 2 48nm、Kr F准分子激光经过石英相位掩膜版的空间调制 ,在载氢增敏处理过的通信光纤与 B/Ge光纤上分别写入光致折变布拉格光栅的实验研究。经实验测定 ,在光栅布拉格波长上 (λH2 =15 46 .45 5 4nm ,λB/Ge=15 45 .15 5 nm) ,两种光栅反射率均大于 99% ,3d B带宽分别为 0 .12 9nm和 0 .182 nm。经比较 ,B/ Ge光纤比氢载光纤具有更好的光敏性和热稳定性