Narrow linewidth gain measurements in KrF and ArF excimer amplifiers pumped longitudinally by high‐power electrons

Single‐pulse KrF and ArF gain measurements have been conducted with an excimer amplifier longitudinally pumped by a high‐power (∼5‐MW/cm3 deposition) electron beam. This amplifier has preserved the narrow linewidth (∼10 GHz) exhibited by the probe laser beam generated by a grating‐tuned, discharge pumped excimer laser. Single‐pass gain was measured at 248.45 nm, the peak of the KrF laser gain profile, for a laser pulse with full width half maximum (FWHM) of 20 ns. Analysis of the gain data by a modified Rigrod steady‐state formulation yielded values for the small‐signal gain, the nonsaturable absorption, and saturation intensity of g0 = 12.6%/cm, α∼0.45%/cm, and Is = 4.1 MW/cm2, respectively, for a 750‐Torr laser mix. The corresponding gain peak measurement for an ArF beam at 193.31 nm with FWHM of 15 ns produced g0 = 12.1%/cm, α∼0.70%/cm, and Is = 6.7 MW/cm2 for a 963‐Torr laser mix with the same stopping power as the KrF mix. Measurement of gain at 193.68 nm, well away from gain peak, resulted in g0= 10...