基于波片棱镜组合能量调节的切趾光纤光栅

为提高飞秒激光制备高反射率 FBG(Fiber Bragg Grating)的边模抑制比, 提出了一种基于组合二分之一波片和格兰棱镜调节激光能量的加工方法, 制备出了高反射率和高边模抑制比的切趾光纤光栅。 通过上位机输入切趾函数模型, 实时精确调节步进电机速度, 机械旋转二分之一波片位置, 实现激光能量沿光纤方向呈切趾函数分布, 从而在光纤纤芯中折射率调制区域呈切趾函数分布, 获得参数可调的切趾光纤光栅。 实验表明,该方法制备的切趾光栅在 1 550 nm 处反射率可达 70% , 边模抑制比超过 20 dB, 半高峰宽度 0. 35 nm。 对其温度和应力传感特性研究显示, 其温度灵敏度为 1. 529*10^-2nm/ K, 应力灵敏度为 1. 61 nm/ N。 该种方法制备的高反射率切趾光纤光栅有望应用于大功率、 窄线宽的光纤激光器以及高速精确传感解调系统中。

Apodized Fiber Grating Based on Energy Adjustment of Combined Wave Plate and Prism

In order to increase the side-mode suppression ratio of FBGs ( Fiber Bragg Gratings) with high reflectivity and reduce the insertion loss caused by preparation of high reflectivity gratings using femtosecondlaser pulses, we present a processing method based on a combination of a half-wave plate and a Glan prism, anapodized fiber grating with high reflectivity, high side mode suppression ratio, and low insertion loss.By inputting the apodization function model to the host computer, the stepper motor speed can be precisely adjusted in real time, and the half-wave plate position can be mechanically rotated to realize the laser energy distribution along the fiber direction as an apodization function. Finally an apodized fiber grating with adjustable parameters is obtained. The experiment shows that the apodized grating of this method can reach 70% reflectance at 1 550 nm, the side-mode suppression ratio is 20 dB with a full width at half maximum of 0. 35 nm. And the temperature and strain sensing characteristics is tested. The temperature sensitivity is 1. 529*10^-2nm / K, and the strain sensitivity is 1. 61 nm / N. This high-reflectance apodized fiber gratings can be expected to be applied in high-power narrow-linewidth fiber lasers and high-speed accurate sensing demodulation system.