高功率掺镱双包层光纤激光器热效应理论研究

Theoretical study on thermal effect in Yb-doped double-clad high power fiber laser

针对高功率双包层光纤激光器热效应严重制约着光纤激光器的输出功率和光束质量这一现象,利用热传导方程和边界条件推导出了双包层光纤激光器温度分布的解析解,进而分析了热效应引起的应力分布,温度和应力引起的折射率变化以及热效应引起的光程差。结果表明,在纤芯轴线处切向、法向、轴向应力分别达到负的最小值,而在光纤表面处径向应力为0,法向、轴向达到正的最大值;应力引起的折射率变化与温度引起的折射率变化相比较小;温度变化是热效应引起光程差主要原因,热膨胀和热应力引起的光程差较小。

Thermal effect of high power fiber laser severely limits the output power and beam quality. Temperature distribution in a double-clad high power fiber laser was analyzed based on thermal conductive equation and boundary condition, and thermal stress distribution was presented by temperature distribution, the change of index refraction induced by temperature and stress was analyzed separately, optic path difference in double-clad high power fiber laser induced by thermal effect was presented. Results indicate that all stresses are compressive, in the fiber core region, however, in the cladding region, the stress is partly compressive and tensile;at the fiber outer boundary, the radial stress is zero while the tangential and longitudinal stress are equal and tensile;the change of index refraction induced by temperature is larger than by stress;optic path difference was caused mostly by the change of temperature, very small by thermal expand and thermal stress.