飞秒激光刻写高阶倾斜光纤Bragg光栅

High-Order Tilted Fiber Bragg Gratings Carved with Femtosecond Laser

报道了一种利用飞秒激光微纳加工技术在非敏化单模光纤中制备的高阶倾斜光纤Bragg光栅（HO—TFBG）。倾斜折射率调制是将聚焦的飞秒激光穿过高阶相位掩模板，并扫描曝光倾斜放置的光纤实现的，其覆盖了全部纤芯和部分包层。该单-HO—TFBG在1200～1700 nm波长范围内可形成三组与高阶Bragg谐振相对应的“包层模式谐振系列”。因此，其携带的信息量远高于紫外倾斜光纤Bragg光栅（uV—TFBG），其功能性更佳，尤其适用于多传感参数的监控。研究了HO—TFBG的折射率、轴向应变和温度等传感特性。此外，该器件兼具飞秒激光诱导光栅结构的高温稳定性，其在苛刻环境中的化学和物理传感具有潜力。

High-order tilted fiber Bragg gratings （HO-TFBG） in non-photosensitized single mode fiber aredemonstrated with femtosecond laser micro-nano machining technique. To realize the tilted refractive indexmodulation in fiber core and partial cladding, a high order phase mask is used to generate periodic light intensitywhich is focused on to the tilted fiber with a lateral scanning. Using this method, three groups of cladding moderesonances in relation with high order Bragg resonance are detected in the wavelength range from 1200 nm to1700 nm. Thus it carries more informations compared with ultraviolet tilted fiber Bragg gratings （UV-TFBG）,especially in multi-parameters monitoring. The refractive index, axial strain and temperature sensing characteristics ofthe HO-TFBG are also studied. Besides, due to the femtosecond laser material modification, this device shows a good abilityin high temperature stability, which has potention in chemical and physical sensing in harsh circumstances.