飞秒激光直写单模化蓝宝石光纤微位移传感研究

doi:10.16553/j.cnki.issn1000-985x.2026.0079

人工晶体学报 ›› 2026, Vol. 55 ›› Issue (7): 1135-1142.DOI: 10.16553/j.cnki.issn1000-985x.2026.0079

飞秒激光直写单模化蓝宝石光纤微位移传感研究

徐静¹(), 高山¹, 张博文¹, 刘严¹, 朱瑶¹, 张智博², 杨菁¹, 关春颖¹()

^1.哈尔滨工程大学物理与光电工程学院，哈尔滨 150001
^2.中国船舶集团有限公司703研究所，哈尔滨 150007

收稿日期:2026-04-30 出版日期:2026-07-20 发布日期:2026-08-04
通信作者: 关春颖，博士，教授。E-mail：cyguan@163.com
作者简介:徐静（2002—），女，山西省人，硕士研究生。E-mail：1845093547@qq.com
关春颖，教授，博士生导师，“龙江学者”特聘教授，中国光学学会纤维光学与集成光学委员会委员，中国光学学会光电技术专委会委员。主持国家自然科学基金重点项目、重大研究计划培育项目、面上项目、国防基础加强等项目20余项。获得黑龙江省科学技术奖一等奖1项，二等奖1项。累计在eLight、Laser & Photonics Reviews、Science Advances等期刊发表研究论文200余篇，获得授权发明专利63项。
基金资助:
国家自然科学基金重点项目(62435012);黑龙江省自然科学基金重点项目(ZD2025F005);中央高校基本科研业务费(3072026ZX2503)

Single-Mode Sapphire Fiber Micro-Displacement Sensing via Femtosecond Laser Direct Writing

XU Jing¹(), GAO Shan¹, ZHANG Bowen¹, LIU Yan¹, ZHU Yao¹, ZHANG Zhibo², YANG Jing¹, GUAN Chunying¹()

^1.College of Physics and Optoelectronic Engineering，Harbin Engineering University，Harbin 150001，China
^2.No. 703 Research Institute of China State Shipbuilding Company Limited，Harbin 150007，China

Received:2026-04-30 Online:2026-07-20 Published:2026-08-04

摘要/Abstract

摘要： 针对高温极端环境下非接触式微小位移测量的需求，本文提出并制备了一种基于飞秒激光直写单模化蓝宝石光纤的反射式空气外腔传感器。利用蓝宝石光纤端面与外部镀金反射镜形成反射式法布里-珀罗空气外腔。通过飞秒激光对蓝宝石光纤进行折射率调制来构建凹陷型包层结构实现4 cm长的单模传输，蓝宝石光纤中多模传输对干涉谱引入的干扰被抑制。测试了不同步长下的位移响应，结果表明：在5 μm步长下，解调腔长与外加位移呈良好的线性关系，线性拟合斜率为1.000 0 μm/μm，拟合决定系数R²为0.999 97。在500、100和50 nm小步长条件下，器件的位移-波长响应灵敏度分别为3.558 3、3.368 5和3.037 6 nm/μm，表明其在亚微米及更小位移范围内仍具有较好的响应与分辨能力。由于蓝宝石光纤高温性能稳定，该传感器在高温环境下非接触式微小位移测量中具有应用潜力。

关键词: 蓝宝石光纤; 位移测量; 单模化; 法布里-珀罗空气外腔; 飞秒激光直写; 凹陷型包层结构

Abstract: Non-contact micro-displacement measurement is important for monitoring critical components in high-temperature harsh environments. Optical fiber sensors are attractive for such applications because of their compact size， electromagnetic immunity， and remote interrogation capability. Reflective Fabry-Pérot sensors with an external air cavity are particularly suitable for non-contact displacement measurement because the variation in the distance between the fiber end face and an external reflector can be converted into a change in the air-cavity length， which can be demodulated from the reflection spectrum. However， conventional cladding-free sapphire fibers support multimode transmission， which may induce mode coupling， spectral fluctuations， and unstable Fabry-Pérot interference signals. In this work， a reflective external Fabry-Pérot air-cavity micro-displacement sensor based on a femtosecond-laser-written single-mode guiding structure in sapphire fiber was proposed and fabricated. The external Fabry-Pérot air cavity was formed between the sapphire fiber end face and a gold-coated mirror. To improve the transmission characteristics of the sapphire fiber， refractive-index modification was introduced inside the fiber by femtosecond laser direct writing. A depressed-cladding structure was constructed in which the laser-modified peripheral region acted as an effective low-index cladding， while the unmodified central region served as the guiding core. With this design， single-mode transmission over a length of 4 cm was achieved， and multimode-transmission-induced interference in the sapphire fiber was effectively suppressed. The resulting clearer interference fringes provided a stable spectral basis for displacement demodulation. The displacement response of the sensor was experimentally investigated under different displacement step sizes. For the 5 μm step test， the cavity length was demodulated by calculating the average free spectral range of the reflection spectrum. The demodulated cavity length exhibited excellent linearity with the applied displacement， with a fitted slope of 1.000 0 μm/μm and a coefficient of determination R² of 0.999 97. These results indicate that the applied displacement can be accurately converted into the variation of the Fabry-Pérot air-cavity length. To further evaluate the response under smaller displacement variations， displacement tests with step sizes of 500， 100 and 50 nm were carried out. In these tests， a selected interference dip was tracked， and the displacement-wavelength response relationship was established. The displacement-wavelength sensitivities are obtained as 3.558 3， 3.368 5 and 3.037 6 nm/μm for the 500， 100 and 50 nm step tests， respectively. These results demonstrate that the proposed sensor provides reliable response and high-resolution tracking capability for displacement steps down to 50 nm. The main innovation of this work is the integration of a femtosecond-laser-written single-mode guiding structure in sapphire fiber with a reflective external Fabry-Pérot air cavity for non-contact micro-displacement measurement. The depressed-cladding structure improves the transmission state of the sapphire fiber and reduces the influence of multimode interference on the reflection spectrum， thereby enhancing the reliability of displacement demodulation. Benefiting from the excellent high-temperature stability of sapphire fiber， the proposed sensing structure shows potential for non-contact micro-displacement measurement in high-temperature environments. This study provides a useful reference for the development of single-mode sapphire-fiber-based displacement sensors for harsh-environment applications.

Key words: sapphire fiber; displacement measurement; single-mode operation; Fabry-Pérot air external cavity; femtosecond laser direct writing; depressed-cladding structure

中图分类号:

TN253

徐静, 高山, 张博文, 刘严, 朱瑶, 张智博, 杨菁, 关春颖. 飞秒激光直写单模化蓝宝石光纤微位移传感研究[J]. 人工晶体学报, 2026, 55(7): 1135-1142.

XU Jing, GAO Shan, ZHANG Bowen, LIU Yan, ZHU Yao, ZHANG Zhibo, YANG Jing, GUAN Chunying. Single-Mode Sapphire Fiber Micro-Displacement Sensing via Femtosecond Laser Direct Writing[J]. Journal of Synthetic Crystals, 2026, 55(7): 1135-1142.

图/表 9

图1 反射式F-P蓝宝石光纤传感器结构示意图。（a）整体结构及光路；（b）改性区域横截面结构

Fig.1 Schematic of the reflection-type Fabry-Pérot sapphire fiber sensor. （a） Overall structure and optical path；（b） cross-section structure of the modified region

图2 飞秒激光加工系统示意图

Fig.2 Schematic of the femtosecond laser processing system

图3 单模化蓝宝石光纤结构显微图。（a）侧视图；（b）端面图

Fig.3 Microscopic images of sensor structure. （a） Side view；（b） end-face view

图4 位移测试系统示意图

Fig.4 Schematic of the displacement measurement system

图5 单模化前、后蓝宝石光纤干涉反射谱对比

Fig.5 Comparison of interference reflection spectra before and after single-mode modification of sapphire fiber

图6 5 μm步长下位移-腔长响应曲线

Fig.6 Displacement-cavity length response curve at a 5 μm step size

图7 500 nm步长下位移响应结果。（a）位移响应光谱；（b）位移-波长关系

Fig.7 Displacement response results at a 500 nm step size. （a） Response spectra；（b） displacement-wavelength relationship

图8 100 nm步长下位移响应结果。（a）位移响应光谱；（b）位移-波长关系

Fig.8 Displacement response results at a 100 nm step size. （a） Response spectra；（b） displacement-wavelength relationship

图9 50 nm步长下位移响应结果。（a）位移响应光谱；（b）位移-波长关系

Fig.9 Displacement response results at a 50 nm step size. （a） Response spectra；（b） displacement-wavelength relationship

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飞秒激光直写单模化蓝宝石光纤微位移传感研究

Single-Mode Sapphire Fiber Micro-Displacement Sensing via Femtosecond Laser Direct Writing

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