Formation of luminescence centers and nonlinear optical effects in silver-containing glasses under femtosecond laser pulses

It is experimentally shown that irradiation of silver-containing silicate glass by IR femtosecond laser pulses leads to generation of free electrons in glass as a result of multiphoton ionization. Free electrons, being captured by charged molecular silver clusters, transform them into the neutral state, as a result of which the luminescence intensity along the laser-pulse track significantly increases. When a laser pulse propagates in glass, cubic nonlinearity dominates in the initial portion of the path, which leads to pulse self-focusing and filamentation. In the final portion of the path, the dominant process is self-defocusing, which is caused by the local decrease in the refractive index as a result of multiphoton generation of free electrons.