| 摘要 |
PURPOSE:To provide the antireflection film for a CaF2-substrate which is usable for optical parts for large-output high-repetition excimer lasers, has the sufficient heat resistance to enable the use of the optical parts even in a high-temp. environment, is mild in the film thickness-controllability at the time of production and is small in the number of layers. CONSTITUTION:The antireflection film is formed of the two-layered structure constituted by successively forming an MgO film as a 1st layer and an SiO2 film as a 2nd layer on an optically polished CaF2 substrate and selecting the optical film thicknesses of the time respectively at 0.33 to 0.38lambda and 0.19 to 0.21lambda ranges (where lambda is a central wavelength). The antireflection film is otherwise formed of the three-layered structure constituted by successively forming an SiO2 film as a low-refractive index material for the 1st layer, an MgO film as a high-refractive index material for the 2nd layer and an SiO2 film as a low-refractive index material for the 3rd layer and setting the respective optical film thicknesses at 0.23 to O.27lambda, 0.35 to 0.40lambda and 0.18 to 0.20lambda ranges. |
