| 摘要 |
PURPOSE:To take out a high quality laser beam stably by using an unstable type optical resonator on a ring shaped light path as a specified output mirror. CONSTITUTION:A laser beam 18 is reflected from a second reflecting mirror 15 in an unstable type optical resonator 16 and amplified in a laser medium 1. Thus a laser beam 17 is obtained. The laser beam 17 is condensed and magnified with a first reflecting mirror 13. Most of the peripheral part of the beam is emitted to the outside as a laser beam 19 through a non-reflecting film 8 at the peripheral part of the inner surface of an output mirror 14. A part of the central part of the beam remains at the outside as a part of the laser beam 19 through a partial reflecting film 7 at the central part of the inner surface of the mirror 14. The remaining part of the beam is guided into the medium 1 again as the beam 18 and circulated in a ring pattern in the oscillator 16. Since the difference between losses of the lower-order mode and the higher-order mode having the aligned phase is large, the mode of the laser beam which is generated after the circulation is only the lowest-order mode. The beam is expanded at every circulation. Therefore, the high quality beam having the large cross sectional area can be obtained. |
