Modifications in lithium niobium silicate glass by femtosecond laser direct writing: morphology, crystallization, and nanostructure

We explore femtosecond laser-induced modifications (i.e., morphology, crystallization, and nanostructure) in lithium niobium silicate glass at high repetition rates (1030 nm, 300 fs, and 300 kHz) to get insight on the ultrafast laser-matter interaction according to the pulse energy and writing configuration (the laser polarization direction versus scanning one). The modifications can be classified into three regimes according to pulse energy: (1) at 0.3-0.4 [mu]J/pulse, one amorphous zone with a larger sensitivity to chemical etching; (2) at 0.5-0.9 [mu]J/pulse, textured nanocrystals embedded in lamella-like amorphous phases whatever the laser polarization or scanning direction is; and (3) at 1.0-2.2 [mu]J/pulse, crystallization dependent on the writing configuration. Remarkably, we show in this paper that the orientation of the nanostructure can be controlled by laser polarization. In addition, this nanostructure is investigated in three dimensions by a combination of scanning electron microscope, electron backscatter diffraction, and transmission electron microscopy. This finding may guide users to the optimal parameters for applications in optics.