Narrow band emission laser, esp. excimer laser for microlithography

摘要

The laser has a laser resonator contg. a laser active medium (10), at least one highly reflective mirror (12), and wavelength selective elements (14,22). Also provided are at least one beam expansion lens (16) and one optical element (18) to rotate the polarisation plane of the beam. The laser resonator can contain a Fabry-Perot etalon (22) as a wavelength selective element, a polarising beam divider, a grid, beam expander and polarisation plane rotation element. The optical element used to rotate the polarisation plane can be a Faraday rotator. The polarising beam divider is arranged to maximally reflect the s-components and maximally pass the p-components of the beam.