Resonator using polarization beam splitter prism for microlithography KrF excimer laser

We discuss a new resonator design for sub-pm bandwidth (FWHM) KrF excimer laser using an etalon, a grating and prisms. This resonator uses a polarization beam splitter prism (PBSP) which has both functions of splitting polarized beam and beam expansion to reduce the resonator length. In our experiments, the output power is improved 29.4% by using PBSP in comparison with the conventional method, while the bandwidth (FWHM) is reduced from less than 0.9pm to less than 0.6pm at the same time. A calculation has been done to confirm the output power dependence on the resonator length and the loss of optics. Its result explains our experimental results approximately. We demonstrated that PBSP has a significant effect to improve the output power of the narrow bandwidth KrF excimer laser that would result in the extension of chamber lifetime. Furthermore, this technique will help the development of the band narrowing excimer laser for microlithography.