一种减少光谱组束光程的方法

A method for reducing the optical path in spectral beam combining

介绍了一种减少半导体激光器阵列光谱组束(SBC)整体光程的方法,即将传统SBC中传输透镜的汇聚和准直作用分离,分别由两个透镜实现。起汇聚作用的透镜将各个发光单元的光束聚焦到光栅上,实现各个发光单元空间上的叠加;起准直作用的透镜在光栅之后将组合后的光束进行准直,使各个发光单元锁定在不同的波长上。由于起汇聚作用的透镜不需要再对各个发光单元的光束进行准直,汇聚透镜与巴条前端面的距离不再需要严格的等于传输透镜的焦距,二者之间的距离可以很近,因此整体的光程可以近似地减少1/2,使利用长焦传输透镜压窄线宽时各发光单元有足够的反馈量,抑制串扰,有利于实现多个巴条的SBC。采用标准的半导体激光阵列,实现连续输出激光功率为49.42 W,电光转换效率为42.7%,光谱线宽为8.5nm,输出光束水平方向光束质量M2x=1.29(0.4 mm×mrad),竖直方向光束质量M2=11.6(3.6 mm×mrad),两个方向的光束质量都与单个发光单元的光束质量接近。

We have demonstrated that the functions of focusing and collimation of the transformer lens in the traditional spectral beam combining systems can be achieved by two optical lenses. One lens focuses all the beams from all emitters on the grating, which makes beams superimposed in space, while the other lens collimates the combining beam after the grating, to ensure a sufficient amount of feedback and make each emitter locked at different wavelengths. The first lens used for focusing doesn＇t need to collimate the beams from all emitters, so the distance between the focusing lens and the front face of diode laser bar is no longer the focal length of the transformer lens and can be very short. So the optical path of the system is reduced by half approximately, which makes it convenient for spectral beam combining of multiple bars. A standard semiconductor laser array is employed in this experiment. Output power of 49.42 W and electro-optic conversion efficiency of 42.7% are achieved. The spectral line-width is 8.5nm.Mx^2 values of 1.29 and 11.6 in horizontal and vertical directions are obtained. The beam quality of the output is close to that of a single emitter of the array in both directions.