直线腔掺铒光纤激光器有源内腔吸收型气体检测灵敏度分析

本文提出一种基于掺铒光纤激光器的有源内腔吸收型全光纤气体检测技术．以掺铒光纤激光器二能级速率方程为基础，理论上分析了腔镜反射率、阈值附近激光增益的非线性效应和模式竞争对气体检测灵敏度的影响．分析表明：改变腔反射镜的反射率可改变激光的反射次数，相当于改变了吸收长度以提高探测灵敏度；阈值附近激光增益的非线性效应对灵敏度的改变具有非线性性，如果不考虑自发辐射，阈值附近探测灵敏度放大倍数理论上可以达到无穷大；模式竞争效应相当于放大了气体的吸收系数，从而使得激光器多模运转时灵敏度比单模运转提高很多倍．

Theoretical Analysis of Sensitivity in an Erbium-Doped Fiber Laser Intra-Cavity Absorption Gas Sensor

An erbium-doped fiber laser intra-cavity absorption spectroscopy for gas sensing is proposed in this paper.The action of the fiber laser sensor is theoretically investigated using two-level system rate equations.The reasons for the enhancement in sensitivity are discussed by defining a sensitivity factor,which are resonator effect,the threshold character of laser process and the competition between laser modes.The results show that changing the reflectivity of cavity mirrors can change the frequency of laser reflection.And detective sensitivity will be enhanced by increasing the path of interaction.The nonlinear characteristic of laser gain near the threshold affects detective sensitivity in a non-linear manner.If spontaneous emission is not considered,detective sensitivity can be infinite when the laser worked near the threshold.The effect of mode competition amounts to the rise of absorption coefficient of gas in in-creasing the detective sensitivity.So the detective sensitivity of a laser under single mode operation is much better than that of a laser under multi-mode operation.