Dynamics of output spectra within a single laser pulse from a line-narrowed excimer laser

We describe the dynamic behavior of spectral line-narrowing during a single laser pulse generated from a line-narrowed KrF excimer laser used in optic al lithography. To study the details of the dynamics, a spectral monitoring system, composed of a Fabry-Perot interferometer, a streak camera, and a n umerical simulation code was developed. In the laser studied, the spectral bandwidth of 1.5 pm in full width at half maximum (FWHM) at the beginning o f the pulse was narrowed to 0.8 pm (FWHM) with the wavelength selective ele ments having a passive transmission bandwidth of about 2.9 pm (FWHM). The r esults of the numerical calculations were in reasonable agreement with the experimental results, and showed that the time-integrated linewidth in the present laser system was narrowed only to 40% of the transmission bandwidth of the spectral selective elements in the cavity.