| 摘要 |
PURPOSE:To generate a laser beam quite stable in geometry and emission direction by a method wherein adverse effects imposed on a laser beam by the discharge section gas temperature distribution is counterbalanced by turn-around attributable to 2nd-4th mirrors. CONSTITUTION:The downstream or high-temperature side of a gas in a light path 10a changes in a light path 10d into an upstream or low-temperature side after inversion in a turn-around path involving 2nd-4th mirrors 21-23. Accordingly, beam displacement attributable to temperature distribution along the direction of a gas flow 6 in a discharge section 2 is counterbalanced as the gas passes through the light paths 10a and 10d. With the 2nd mirror 22 being positioned outside the discharge section 2 in a light path 20b, the section of the light path 10b in the discharge section 2 is smaller, compensation involving temperature distribution may be ignored. Even when there is an increase in the discharge power for a higher-level laser output, there will virtually be no asymmetry in the cross section of a laser beam 10 or a change in the emission angle. |
