808nm大功率半导体激光迭阵偏振耦合技术

随着半导体激光器在工业、军事、核能等领域的应用越来越多,单个迭阵输出的光功率密度已经不能满足实际的需求,这就需要将多个半导体激光迭阵的光束耦合成为一个共同的光束,以提高输出功率和亮度.所以采用怎样的光束耦合技术能实现高亮度、高质量的激光输出就成了一个关键性的问题.对于该技术的研究,国内还没有实验方面的报道.主要介绍了大功率半导体激光器偏振耦合原理、实验的技术路线,以及对808nm半导体激光迭阵进行耦合实验的结果及分析.对2个bar、功率为40W/bar的808nm连续半导体激光迭阵,实现偏振耦合的总效率超过90%,聚焦得直径为3mm光斑,输出功率达到134W,总体效率超过84%.对7个bar、峰值功率100W/ba、r占空比20%的808nm准连续半导体激光迭阵进行了偏振耦合,其效率达到67%,得到4.5mm×4.5mm的光斑.

808 nm High Power Diode Laser Stack with Polarization Coupling

High-power diode lasers based on GaAs semiconductor bars meanwhile are well established as reliable and highly efficient laser sources.Continuous improvement of the semiconductor material itself as well as mounting and cooling techniques during the last years have led to increased output power and high lifetimes.In many cases high power diode lasers are on the way to replace flashtubes for solid state laser pumping.By realizing arrangements of many high-power diode laser elements,e.g.diode laser stacks,the overall output power can be increased further up to the kW range.In this power level,we can have many important applications,such as surgery,welding of polymers,soldering,coatings and surface treatment of metals.But there are some applications,which require much higher power and brightness,e.g.hardening,key hole welding,cutting and metal welding.In addition,high power diode lasers in the military also have important applications.So all developed countries have attached great importance to high-power diode laser system and its applications.Germany is developing initiative "BRIOLAS"(brilliant diode lasers)program,the German Federal Ministry of Education and Research (BMBF) is supporting the BRIOLAS-initiative with about 30 M.The United States have launched "SHEDS"(High Efficiency Diode Sources)from 2005.Now Germany laserline corporation have products,that direct diode laser system have largest output power of 10000 W,and fiber coupled diode laser system have largest output power of 8 000 W into the 1.5 mm diameter of the fiber.We know that under certain circumstances the light,which is emitted from the diode laser bar is linearly polarized,and the polarization degree can be 95%~98%.So polarization coupling technology makes two laser beam of perpendicular polarization direction reciprocally together,that is another effective way to improve the power and the brightness of diode lasers.After fast axis collimating,the polarization direction of one laser stack is rotated 90°through a half-wave plate,thus,the polarization directions of two laser stack are vertical reciprocally.The beams of two lasers are incident to polarization filter;one transmits through it,and the other is bent on it.Finally two beams combine to one.In this paper,it mainly introduces the principle of polarization coupling,technique route,experiment result and analysis.The polarization coupling efficiency can achieve 90% for two LD stacks with seven bars whose emission wavelength is 808 nm.The efficiency of 67% can be achieved after focusing to the beam size of 4.5 mm×4.5 mm.