Development of UV Saturable Absorber Acridine and Its Application for a Short Pulse KrF Laser

Abstract

A derivative of the linear tri-cyclic compound acridine in several different solvents is shown to be as an effective saturable absorber for short pulse KrF lasers. Acridine dissolved in ethanol showed the best bleaching characteristics for a 20 ps laser pulse, the ratio of primary to the excited absorption cross-section of 7.3:1 and the low saturation fluence of 1.1mJ/cm² due to the large absorption cross-section of 5.6 × 10^-16cm² at 249nm. Temporal behavior of the absorption recovery showed two time constants of 0.4ns and 115ns, the fast component corresponded to the measured fluorescence decay time of 0.43ns for the first excited singlet state. The ASE free operation (less than 0.1% of the laser energy) and the pulse compression in a saturated amplifier have been demonstrated. The laser pulse width was compressed by a factor of 4 in an absorber-amplifier arrangement.