Multi-band expand system for high-power lasers

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 copper 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 λ/40 as the be