Gas discharge laser, such as excimer laser or molecular fluorine laser, has e.g. adjustable diverging lens and converging lens in resonator to compensate for thermal lens effect

摘要

One or more lenses (22a,22b) are provided in the resonator (16,18) of the laser, to compensate for the thermal lens effect. The position and/or focal length of at least one of the lenses may be adjustable. The lenses may include a diverging lens (22a) and a converging lens (22b).