飞秒直写长周期光纤光栅及其液体折射率特性研究

利用800 nm飞秒激光在未经载氢处理的HI1060光纤中制作了长周期光纤光栅(LPFG).采用逐线刻写方式实现了谐振波长为1 548.4 nm的LPFG,谐振强度为12 dB,栅区长度小于4 mm.使用不同折射率的氯化钠溶液、蔗糖溶液和酒精溶液分别对LPFG的折射率特性进行了测试和研究.实验中随着三种溶液折射率增加,LPFG的谐振波长发生红移,该LPFG在氯化钠溶液、蔗糖溶液和酒精溶液中的折射率灵敏度分别为175.34、175.31和331.89 nm/RIU.实验结果表明,这种基于飞秒激光制作的LPFG对液体折射率变化有较高的灵敏度,可用于液体折射率传感测试.

LPFG Fabricated by Femtosecond Laser and its Characteristics of Refractive Index of Liquid

The long period fiber grating (LPFG) was fabricated by using the 800 nm femtosecond laser with line-by-line method in the non-hydrogen-loaded HI1060 fiber. The resonance wavelength of the LPFG is 1 548.4 nm, the resonance intensity is 12 dB, and the length of the grating region is less than 4 mm. The refractive index properties of LPFG were tested and studied by using different refractive index of NaCl solution, sucrose solution and alcohol solution. In the experiment, the resonance wavelength shifts toward longer wavelength with increases of the refractive index of three kinds of solution. The refractive index sensitivity of three kinds of solution is up to 175.34 nm/RIU, 175.31 nm/RIU and 331.89 nm/RIU respectively. The experimental results show that the LPFG based on the femtosecond laser has excellent sensitivity with the refractive index change of liquid, and can be used for the sensitive measurement of the liquid refractive index.