自反馈增强的高消光比45°倾斜光纤光栅刻写方法  

Self-Feedback Enhanced High Extinction Ratio 45° Tilted Fiber Grating Inscription Method

作　　者：陈琳[1] 郑红蓉 姜碧强[1] 赵建林[1] Chen Lin;Zheng Hongrong;Jiang Biqiang;Zhao Jianlin(Key Laboratory of Light Field Manipulation and Information Acquisition,Ministry of Industry and Information Technology,School of Physical Science and Technology,Shaanci Key Laboratory of Optical Information Technology,Northwestern Polytechnical University,Xi'an 710129,Shaanxi,China)

机构地区：[1]西北工业大学物理科学与技术学院光场调控与信息感知工业和信息化部重点实验室,陕西省光信息技术重点实验室,陕西西安710129

出　　处：《光学学报》2024年第13期80-87,共8页Acta Optica Sinica

基　　金：国家自然科学基金(61975166,62322510,62375223)。

摘　　要：作为偏振相关器件,偏振消光比(PER)是评估45°倾斜光纤光栅(45°TFG)性能的核心指标。为提升45°TFG的PER,分析了光栅刻写过程中入射紫外光偏振态及多次刻写位置重复性对刻写效果的影响,将偏振控制元件及高精度压电位移台融入光栅刻写系统,利用实时监测的PER数据,动态反馈控制光栅掩模版位置,通过多程重复刻写提高光栅折射率的调制度。刻写而成的45°TFG的中心波长为830 nm,长度仅为30 mm,PER优于35 dB,插入损耗低于2 dB,3 dB谱宽优于60 nm,可满足光纤陀螺等光纤传感器的应用需求。所提出的基于掩模版位置自反馈的45°TFG多程刻写增强方法,自适应地降低了刻写系统对稳定度的要求,为高消光比45°TFG的高重复性量产提供了解决方案。Objective 45° tilted fiber gratings(45° TFGs) are an important class of polarization-dependent-loss-based polarizers.Unlike other fiber polarizers that require physical modifications to the fiber such as tapering, polishing, and etching the fiber, 45° TFGs can be fabricated noncontactly inside the fiber core with ultraviolet(UV) light exposure, preserving the mechanical strength of the fiber itself. This makes the 45° TFG-based polarizers ideal for applications that prioritize reliability and repeatability, such as polarization-mode-locking fiber lasers and polarization mode filtering in fiber-optic sensing. 45° TFGs utilize the Brewster angle effect, where the s-component of the light propagating in the gratings is resonantly radiated out, and in contrast, the p-component can propagate losslessly in theory. Thus, the contrast between these two polarization components, i.e., polarization extinction ratio(PER), is a fundamental parameter for evaluating the performance of the 45° TFGs. Unlike traditional fiber Bragg gratings, in which their key parameter, reflectivity, grows exponentially with the grating's index modulation, the PER of 45° TFGs only grows with the square of their index modulation. Hence, a strong index modulation is often required to have a satisfactory PER for many applications. We propose a highly repeatable method to enhance the index modulation of the 45° TFGs and their PER by multi-pass UV light scan.Method Conventional methods for fabricating fiber Bragg gratings(FBGs) include the two-beam interference method,point-by-point writing method, and scanning phase mask method. Specifically, the scanning phase mask is an important technique for fabricating low insertion loss 45° TFGs. It utilizes a tilted phase mask to spatially modulate UV light,creating the desired grating pattern. The UV light is then scanned along the length of the fiber to fabricate a 45° TFG. Due to the limitations of the grating writing system's stability, traditional writing methods only employ single-pass scanning

关 键 词：光纤光学 45°倾斜光纤光栅 消光比 自反馈 相干衬比度 

分 类 号：O439[机械工程—光学工程]