| 摘要 |
PURPOSE: To obtain an optical element having sufficient reflectivity or transmissivity and further high laser beam durability by using substance contg. a stoichiometric ratio of fluorine to metal or a substance contg. fluorine more than the stoichiometric ratio to form the film of an optical element. CONSTITUTION: The film of a compd. of fluorine and metal is formed on a substrate. The compd. having a stoichiometric composition or the compd. contg. fuorine in excess of stoichimetry are used in this case. The compd. of fluorine and metal is shown by NdFy ((y) is 3 to 3.1) or AlFz ((z) is 3 to 3.1). Namely, this antireflection film is obtained, for example, by forming the film of NdF3 12 Nd: F=1:3 to 3.1) as the high-refractive-index substance on a synthetic quartz substrate 11 with the surface polished with high precision in the optical film thickness of λ/4 (λ=193.4nm) and then forming the film of AlF3 13 (Al:F=1:3 to 3.1) as a low-refractive-index substance on the film 12 in the optical film thickness of λ/4. |
