Subpicosecond pulse generation of KrF amplifier using acridine saturable absorber

ABSTRACT A derivative of the linear tn-cyclic aromatic dye, acridine, was applied to the saturable absorber for KrFlasers. Acridine in ethanol showed the best bleaching properties such as the high cross section ratio F =7.1and the low saturation fluence of 1. 1 mJ/cm2 due to the large absorption cross section of 5. 6 X 1O' cm2 at248 nm. Absorption recovery had two time constants of 0.4 ns and 115 ns. Effective filtering of ASE made itpossible to control the prepulse during the ultra short pulse amplification. Picosecond pulses with sharpfront edge were compressed 10 ps to 420 fs in the saturated gain KrF amplifier. Sub-picosecond pulses withhigh contrast ratio to ASE were generated in the high gain operation of KrF lasers. 1. INTRODUCTION The KrF excimer laser which has a wide band spectrum owing to its bound-free transition has acapability of amplification of ultra—short pulseless than a hundred femtosecond. Gas lasers have some advantages for such a short pulse ampli- fication,'4 because it is much easier to constructsuch a wide aperture laser that the power density