Subjected to ultrafast laser pulses, quartz glass can take on metallic properties, turning briefly from electrical insulator to conductor. A team at the Vienna University of Technology had previously demonstrated this effect, and is now studying this further using large-scale computer simulations, in collaboration with a team from the Tsukuba University in Japan. Quartz glass — typically an insulator that does not conduct electric current — can be fundamentally changed at the femtosecond time scale when subjected to ultrashort laser pulses, the researchers said. Computer simulations show the electron flux from one atom to the others. Images courtesy of the Vienna University of Technology. As this process happens extremely fast, the researchers are now using slow-motion video to study exactly what is happening with the quartz glass. If the laser pulse is strong enough, the quartz turns opaque and briefly behaves like metal. Electrons once bound to oxygen atoms in the quartz change over to other atoms and behave almost like free electrons. After the pulse, the material almost immediately returns to its previous state. “The laser pulse is an extremely strong electric field, which has the power to dramatically change the electronic states in the quartz,” said Dipl.-Ing. Georg Wachter, a doctoral candidate at TU Vienna. “The pulse can not only transfer energy to the electrons, it completely distorts the whole structure of possible electron states in the material.” Experiments will now be conducted with different materials to see how the glass-to-metal effect can be induced more efficiently. The work was published in Physical Review Letters (10.1103/PhysRevLett.113.087401). For more information, visit www.tuwien.ac.at.
CO2 Laser Sources