Krypton fluoride laser pulse shortening by stimulated thermal scattering on a liquid surface.
Pulse shortening of the backscatter of a KrF excimer laser beam focused on the surface of n-hexane is reported. Simultaneous measurements of the backscattered beam, a Fresnel reflected beam, incoherent scattered photons from a liquid surface, and a transmitted beam are performed. The results show that the surface reflected beam disappears followed by beam expansion and the transmitted beam is reduced to form a filamentlike structure with the onset of backscatter. The pulse width of the backscattered beam shows a clear dependence on the focal position in the liquid. Incoherent scattering is sharply enhanced when the laser beam is focused at the liquid surface where the backscattered beam is especially short. The observed phenomena indicate that stimulated thermal scattering is the pulse shortening mechanism.
Shortening of KrF(*) laser pulses using stimulated Brillouin scattering.
Pulses as short as 43 psec were generated by Brillouin backscattering at 248 nm in cyclohexane. The measurements show that the process is accompanied by considerable spectral broadening of the reflected radiation.
Generation of a 300-psec pulse by direct mode locking of a long-pulse XeCl laser.
A pulse duration of 300 psec has been achieved by direct mode locking of a long-pulse (150-nsec) XeCl laser by using an acousto-optic modulator and a saturable absorber (BBQ). The pulse duration was found to depend considerably on intensity level, and the shortest duration was observed in a train with 4-5 pulses. The time evolution of successive pulses pursued by a streak camera showed that a drastic reduction in the pulse duration occurred after the peak pulse in the train.