The advantages and disadvantages of transmission and reflection expand system are analyzed for high-power laser. The secondary mirror is selected in the form of convex paraboloid and the primary mirror in the form of concave paraboloid, which the whole system is Cassegrain system without focus. The parameters of optical system are designed by ZEMAX software based on the expanding ratio and wave aberration. The base material and coating of mirror is analyzed for high-power laser and the cop-per is selected as the substrate. Then the optimal design is conducted for the coating of mirrors, which the reflectivity is above 98% for the near-infrared to far-infrared waveband. The designed optical system is measured by the interferometer with the smoothness of mirror RMS better than A/40 as the benchmark mirror. The experimental results show that the measured expand ratio 3. 53 and wave aberration 0. 206A (λ = 0. 632 8 μm) of this expand system can meet the requirement of multi-band high-power laser.%对透射式和反射式扩束系统应用于高功率激光扩束的优缺点进行了对比研究.采用次镜为凸抛物面,主镜为凹抛物面的无焦卡塞格林系统,运用ZEMAX光学设计软件,按激光扩束系统的扩束倍率和系统的波像差要求,设计出多波段高功率激光扩束系统.对用于高功率激光反射镜的基底材料进行分析,选用无氧铜作为基底材料；采用金增强的膜系设计,膜系从近红外到远红外宽光谱波段激光的反射率均在98％以上.面形精度均方根值优于λ/40(λ=0.632 8μm)的平面镜作为基准镜,采用光学干涉方法对设计的激光扩束系统进行检测实验,结果表明:该扩束系统的扩束倍率为3.53,波像差为0.206λ,满足多波段高功率激光光束发射要求.
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