ASSEMBLY, EXCIMER LASER, METHOD FOR IMPROVING BEAM PROFILE OF LIGHT BEAM AND REDUCING SPECTRUM BAND WIDTH IN EXCIMER LASER, AND METHOD FOR OPERATING LASER

摘要

PROBLEM TO BE SOLVED: To allows a spectrum band width to be constant in various laser emission conditions by allowing a light beam with specified wavelength to be reflected and enter a laser chamber, and allowing light with undesired wavelength to be reflected in a direction not to allow incidence thereof. SOLUTION: An excimer laser generates a beam 100 during operation. The beam 100 is reflected by an optical resonator provided with an Echelle grating 110. In a beam expander 120, a part of laser beam passes through prisms 122, 124 and 126 and enters the grid 110. A mirror 140 changes the direction of beam emitted from the prism 126 and allows it to enter the grid 110. A light beam with desired small wavelength width is reflected on the Echelle grating 110, and it passes through the prism again and enters a laser chamber, and on the other hand, the substantially whole of light beam with undesired wavelength is reflected in the direction not to reenter the laser chamber.