976 nm宽条形高功率半导体激光器的光束质量M^2评价

Evaluation of Beam Quality M^2 for 976 nm Wide Stripe High Power Semiconductor Laser

为了提高976 nm宽条形高功率半导体激光器的光束质量,基于严格的二阶矩理论搭建了一套适用于高功率半导体激光器的光束质量检测装置。利用该装置测量了实验室研制的976 nm宽条形高功率半导体激光器在1～10 A工作电流下的束腰位置、束腰尺寸和远场发散角。实验结果表明,随着电流从1 A增加到10A,快轴方向束宽及远场发散角由于反导引效应有微小增加,但由于垂直方向较强的折射率导引机制使得光束参数变化很小,光束质量因子M^2仅从1. 32增加到1. 48,光束质量基本不变。慢轴方向由于反导引效应及热透镜效应而导致高阶模式激射,使得束宽及远场发散角随工作电流增加逐渐增大,光束质量因子M^2从5. 44增加到11. 76,光束质量逐渐变差。傍轴光束定义及非傍轴光束定义下的光束质量因子测试结果表明,在快轴方向,两者差别较大,不能使用傍轴光束定义近似计算;在慢轴方向,两者近似相等,可以使用傍轴光束定义近似计算。

In order to improve the beam quality of 976 nm wide stripe high power semiconductor laser,a beam quality measurement setup for high power semiconductor lasers is constructed based on the strict second moment theory.This setup is used to measure the beam waist position,beam waist size and far field divergence angle of 976 nm wide stripe high power semiconductor lasers prepared by our lab.The experimental result shows that with the increase of current from 1 A to 10 A,the fast axis beam width and far-field divergence angle increase slightly due to the anti-guidance effect,but the beam parameters change very small because of the strong refractive index guidance mechanism in the vertical direction.The beam quality is almost unchanged,when the beam quality factor M 2 is only increased from 1.32 to 1.48.In slow axis direction,the beam width and far field divergence angle increase gradually with the increase of operating current due to the high-order mode lasing caused by the anti-guidance effect and the thermal lens effect.The beam quality becomes worse,when the beam quality factor M 2 is increased from 5.44 to 11.76.The difference of the beam quality factor is compared with the definition of paraxial beam and non-paraxial beam.The results show that there is an obvious difference by different beam definitions in the fast axis direction and the paraxial beam definition is not suitable for the calculation.In the direction of slow axis,the results are approximately equal and can be approximately calculated by using the paraxial beam definition.