飞秒激光刻写布拉格光栅反射光谱特性研究  

Reflection Spectral Characteristics of Bragg Gratings Fabricated via Femtosecond Laser Phase Mask Technique

作　　者：董欣然 王子安 曾理 孙小燕[2,3] Dong Xinran;Wang Zian;Zeng Li;Sun Xiaoyan(College of Mechanical and Electrical Engineering,Central South University of Forestry and Technology,Changsha 410018,Hunan,China;State Key Laboratory of High Performance Complex Manufacturing,College of Mechanical and Electrical Engineering,Central South University,Changsha 410083,Hunan,China;State Key Laboratory of High Performance Complex Manufacturing,Central South University,Changsha 410083,Hunan,China)

机构地区：[1]中南林业科技大学机电工程学院,湖南长沙410018 [2]中南大学机电工程学院,湖南长沙410083 [3]中南大学高性能复杂制造国家重点实验室,湖南长沙410083

出　　处：《中国激光》2023年第19期100-105,共6页Chinese Journal of Lasers

基　　金：国家自然科学基金青年基金(52005521);湖南省自然科学基金青年基金(2021JJ41079)。

摘　　要：利用飞秒激光相位掩模加工方法制造光纤布拉格光栅(FBG),并研究了激光能量和曝光时间对FBG波长、反射率和带宽的影响规律。研究发现,随着曝光时间的增加,光纤的折射率调制量逐渐变大,耦合效率增大,反射率逐渐变大。当光纤耦合效率达到饱和时,反射率保持不变;当过曝光时,反射率轻微减小,光纤的平均有效折射率和折射率调制深度均变大,带宽增大。随着激光能量的增大,达到最大反射率所需要的曝光时间缩短,且FBG波长的红移量越多,带宽就越大。过大的激光能量会使平均有效折射率和折射率调制深度变大,从而导致FBG主谐振峰两边的旁瓣增多,影响光谱质量。另外,短波方向旁瓣的振荡比较显著,而长波方向则比较平顺。因此,在实际加工中需要选择合适的激光曝光能量和曝光时间。实验获得的最大FBG反射强度达到15 dB,且其光谱变化和理论分析一致。该研究为高质量FBG的制造和光谱特性优化提供了实验依据。Objective Fiber Bragg gratings(FBGs)exhibit the advantages of small size,reflection operation,high sensitivity,and wavelength encoding.Further,the FBGs induced by femtosecond laser pulses have unique advantages,such as high-temperature resistance and high-temperature stability,which are particularly suitable for sensing applications under extreme operating conditions,and thus,these FBGs have been widely used in aerospace and other fields.Fabricating FBGs via phase mask technology has the merits of effective processing and high device consistency and has been demonstrated to be the most promising industrial technology scheme.However,limited research has been conducted on the spectral characteristics of FBGs.We fabricate FBGs via the femtosecond laser phase mask method and extensively study the influence of laser energy and exposure time on the wavelength,reflectivity,and bandwidth of the FBGs.The factors influencing the FBG spectrum are theoretically and experimentally analyzed.This study offers an experimental basis and guidance for the fabrication of high-quality FBG devices using femtosecond laser technology.Methods In this study,FBGs fabricated via the femtosecond laser phase mask method are experimentally demonstrated.The light path of the grating processing system comprises a femtosecond laser system,aperture,optical attenuator,cylindrical lens,and phase mask.The spectrum testing system comprises an amplified spontaneous emission(ASE)broadband light source and an optical fiber spectrum analyzer.The laser system outputs 800 nm femtosecond laser pulses.A diaphragm and optical attenuator are used to control the spot diameter and adjust the laser pulse energy,respectively.Meanwhile,a cylindrical lens is used to focus the light beam,and a phase mask to form interference fringes and periodic structures in the fiber,and writing the gratings.In addition,a spectral testing system is used to monitor the spectral changes of the FBG in real time.In the experiment,when the laser energy is set to 600 mW and the longest ex

关 键 词：光纤光学 光纤布拉格光栅 飞秒激光 相位掩模法 光谱特性 带宽 

分 类 号：TN2[电子电信—物理电子学]