Local Formation of Birefringent Structures in Alkali-Silicate Glass by Femtosecond Laser Beam

Abstract

It is demonstrated that a femtosecond laser beam forms in alkali-silicon glass with different Na₂O concentration microregions that possess birefringence associated with the formation of nanolattices. The phase shift of such regions is determined as a function of the number and energy of the laser pulses. The minimum number of pulses required for birefringence to appear increases with increasing Na₂O concentration. At 10⁷ pulses the phase shift reaches approximately the same maximum value for all glass compositions, which indicates that the diffusion of alkali ions in the process of formation of nanolattices plays a leading role in such glasses.