飞秒激光直写长周期光纤光栅及其光谱特性

Fabrication of Long Period Fibre Gratings by Femtosecond Laser Writing Directly and Its Spectral Characteristics

基于800nm飞秒激光脉冲,设计并搭建了长周期光纤光栅制备系统,该系统通过采用20倍率的显微物镜将飞秒激光脉冲诱导入标准单模光纤纤芯位置,采用水平、垂直双CCD视频监控方式实现对飞秒激光脉冲刻蚀长周期光纤光栅的逐点监测,对未载氢处理的标准单模光纤进行了不同周期、不同周期长度和不同占空比刻写实验.研究结果表明,当选取激光脉冲能量为1.3mW、光栅周期为500μm、光栅占空比为0.6时,该光栅在谐振波长1 300nm处最大谐振峰强度为11.65dB,带外损耗低于2dB,且光栅谐振波长随光栅长度不发生明显漂移;通过光栅占空比的调整,可实现刻写光栅光谱特性的优化设计,使得谐振峰由多峰转为单峰.

The experimental system to write long-period fiber gratings was set up based on femtosecond laser pulses with a central wavelength 800 nm.In this system,the femtosecond laser pulses were induced in the fiber core of the normal SMF-28 by adopting a micro-objective of 20×,and the processing of writing long-period fiber gratings was monitored by adopting the horizontal and vertical dual-CCD video.The long-period fiber gratings with different period,different period number and different duty ratio were inscribed in no-hydrogen-loaded SMF-28 fiber.The experiment result shows that the maximum resonance peak loss of 11.65 dB will be generated at the wavelength of 1 300 nm and out-of-band loss is lower than 2 dB when the laser pulse energy is selected of 1.3 mW,the period of grating is 500μm and the duty ratio of grating is 0.6,and the resonant wavelength of grating is not apparent drift with the length of the grating.More further,the optimal spectral characteristics of grating can be designed through the adjustment of grating duty ratio,and the resonance peak will be changed from multi-peak to single peak.