| 摘要 |
An optical element is configured to have a base composed of a LuAg substrate having a refractive index of 2.14±0.01 for a wavelength of 193 nm and an antireflection film formed on the base, and the optical element being configured to contact a liquid having a refractive index of 1.64±0.01 for the wavelength of 193 nm. The antireflection film includes a high refractive index layer that is formed on the base, contains Al2O3 having a refractive index of 1.87 to 1.92 for the wavelength of 193 nm, and has an optical film thickness of 0.21lambda to 0.34lambda for a design center wavelength lambda of 193 nm and a low refractive index layer that is closer to the liquid than the high refractive index layer, contains Al2O3 having a refractive index equal to or smaller than 1.78 but larger than the refractive index of the liquid for the wavelength of 193 nm, and has an optical film thickness of 0.29lambda to 0.52lambda at the design center wavelength lambda.
|
