Abstract: 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 0.21? to 0.34? for a design center wavelength ? 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 0.29? to 0.52? at the design center wavelength ?.

Abstract: An optical device that includes a low refractive index film is produced at a low cost. To attain this object, in a process of producing an optical device that includes a multilayer film in which low refractive index films and high refractive index films are alternately laminated, a porous film is formed on a substrate by a sputtering deposition system which uses a target unit. The porous film is immersed in a liquid to lower the refractive index of the film. By forming in simple steps a low refractive index film that is lower in refractive index than conventionally used films, a high quality optical device can be obtained at a low cost.

Abstract: 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 0.21? to 0.34? for a design center wavelength ? 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 0.29? to 0.52? at the design center wavelength ?.

Abstract: An optical element includes a multilayer film, and a substrate, wherein the multilayer film includes a first thin film that is formed on the substrate, and made of fluorine-doped oxide or nitride, and a second thin film that is formed on the first thin film, and made of a fluoride material.

Abstract: An optical element includes a multilayer film, and a substrate, wherein the multilayer film includes a first thin film that is formed on the substrate, and made of fluorine-doped oxide or nitride, and a second thin film that is formed on the first thin film, and made of a fluoride material.

Abstract: A method for manufacturing an optical element formed of CaF2 is provided, the optical element exhibiting a small optical loss even when being processed with plasma treatment such as sputtering or plasma cleaning. The method for manufacturing an optical element, described above, has the steps of polishing a CaF2 substrate and performing plasma treatment, such as sputtering or plasma cleaning, in a chamber in which the polished CaF2 substrate is placed. In the polishing step, the thickness of a process-altered layer formed on a surface of the CaF2 substrate is polished so as to be 30 nm or less, and hence there is provided a method for manufacturing an optical element capable of preventing degradation of the optical properties caused by plasma treatment.

Abstract: A method for manufacturing an optical element formed of CaF2 is provided, the optical element exhibiting a small optical loss even when being processed with plasma treatment such as sputtering or plasma cleaning. The method for manufacturing an optical element, described above, has the steps of polishing a CaF2 substrate and performing plasma treatment, such as sputtering or plasma cleaning, in a chamber in which the polished CaF2 substrate is placed. In the polishing step, the thickness of a process-altered layer formed on a surface of the CaF2 substrate is polished so as to be 30 nm or less, and hence there is provided a method for manufacturing an optical element capable of preventing degradation of the optical properties caused by plasma treatment.