| 摘要 |
PURPOSE:To minimize the deviation of an optical axis by providing an orthogonal type folding mirror 23 wherein a pair of reflecting surfaces approximately perpendicular to each other are so arranged as to be directed toward a laser medium, sequentially reflect a laser beam incident from the direction of the laser medium and transmit the reflected beam in the direction of the laser medium. CONSTITUTION:By using an orthogonal type rear folding mirror 23 on one end of an optical resonator, when, for example, a laser beam incident on a second reflecting mirror 33 passes distorted light paths P3 and P4, the laser beam reflected from a first reflecting mirror 31 follows also the distorted light path P4 parallel to the light path P3. Since the light path P4 is bent toward the low temperature side T1 of a gas flow A quite the same as the incident light path P3, when the laser beam reaches the folding mirror 27, the light path P4 becomes parallel to an undistorted light path P2. Accordingly, even though an unevenness is generated in a spatial temperature distribution in a laser medium and the light path of the laser beam is distorted, a deviation in the alignment of an optical system can be restricted to minimum.
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