| 摘要 |
PURPOSE:To limit a plane of polarization of a laser beam radiated from a laser oscillator by a method wherein a difference in reflectance between an S-wave and a P-wave which are incident on one return mirror deciding a direction of linear polarization is made larger than a difference in reflectance between an S-wave and a P-wave which are incident on another return mirror. CONSTITUTION:The selectivity of polarization of one return mirror 23a deciding a plane of linear polarization of a laser beam 10 radiated from a laser oscillator is more excellent than that of another return mirror 22a. That is to say, a difference in reflectance between an S-wave and a P-wave of a laser beam 10c at the return mirror 23a is constituted to be larger than a difference in reflectance at the return mirror 22a. Accordingly, if the return mirror 23a is a mirror composed of molybdenum Mo and the return mirror 22a is a mirror composed of copper Cu coated with gold Au, a plane of polarization of the laser beam 10 radiated from the laser oscillator is decided in a direction of the S-wave at the return mirror 23a, i.e. in a direction parallel to an electric discharge (perpendicular to gas flows 6). |
