Single-Pulse Direct Laser Writing of the Controlled Birefringence in Microvolume of Silica Glass by a Linearly Polarized Femtosecond Laser Beam

Abstract

The formation of stable birefringent micromodifications (voxels) in silica glass by single ultrashort laser pulses with a flat-top intensity profile has been studied experimentally and theoretically as a function of the focusing numerical aperture. It is experimentally shown that birefringence is formed in a voxel if the focusing numerical aperture is higher than 0.5, while lower-aperture focusing gives rise to voxels without birefringence. The slow axis of birefringence is predominantly oriented along the polarization of the incident light, and the azimuthal dispersion of the axis direction decreases with increasing numerical aperture.