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.
Spectrum narrowing and phase conjugation of KrF excimer laser radiation
An electric-discharge KrF laser system with an output energy of 140 mJ in a 20-ns pulse, a beam divergence of 0.1 mrad, and a radiation line width of 0.02 cm−1 is described. Stimulated Brillouin scattering was studied in gaseous SF6 at p = 10 atm. The reflection coefficient of the stimulated scattering mirror was 85% and the laser pulse duration was reduced to 1.5 ns. Phase conjugation of the radiation was studied in liquid n-hexane. It was found that the scattered radiation frequency exhibited no Brillouin shift which might be due to the major contribution of stimulated thermal scattering in n-hexane.
The Italian Renaissance: Culture and Society in Italy
In this newly revised edition of his widely acclaimed work, Peter Burke presents a social and cultural history of the Italian Renaissance. He discusses the social and political institutions that existed in Italy during the fifteenth and sixteenth centuries, and he analyzes the ways of thinking and seeing that characterized this period of extraordinary artistic creativity. Developing a distinctive approach, the author is concerned not only with the finished works of Michelangelo, Raphael, Leonardo da Vinci, and others, but also with the social background, patterns of recruitment, and means of subsistence of this "cultural elite." He thus makes a major contribution both to our understanding of the Italian Renaissance and to our comprehension of the complex relations between culture and society. An excellent social history of the lives and culture of the artists and artisans which made it possible for the arts to flourish.