温度梯度对光纤激光器横向模式的影响

Effects of Temperature Gradient on Transversal Modes in Fiber Lasers

分析了温度梯度对光纤激光器横向模式的影响。通过建立简化的光纤截面热传导模型，得到了光纤截面温度的分布。利用场分析软件分析了在不同抽运功率、吸收系数、折射率温度系数下光纤激光器横向模式的变化，发现当抽运功率提高时，横向模式有向纤芯收缩的趋势，这可能是高功率条件下光纤激光器中高阶模式出现的原因之一。当吸收系数增加或折射率温度系数增加时，横向模式也有向纤芯收缩的趋势。

The impact of thermal induced temperature gradient on the properties of transversal modes propagating in fiber lasers is carefully investigated. The thermal distribution in the cross section of fiber laser is figured out through a predigested heat conductive model, and then, the properties of transversal modes are analyzed by using multiphysics software under different operating conditions or parameters of fiber. It is found that all the transversal modes have a trend of constriction to the core of fiber with rising power level, and this discovery may give one of the explanations how the high order modes appear in single mode high power fiber lasers. As well, when the absorption coefficient or the refractive index-temperature coefficient is growing, the transversal modes also present a constriction trend.