Effect of linear laser polarization angle on internal ultrashort-pulsed laser processing of bulk quartz crystal

The effect of varying the relative angles between the linear polarization state of a laser beam, write-direction, and the optic-axis (C-axis) when ultrashort-pulsed laser processing crystalline quartz is investigated. Various 1030 nm pulse energies were used at 420 fs, 5 MHz with 2 mm/s write-speed. Strongly varying, and closely correlated, pulse energy thresholds for modification and damage are identified for angles of 0° to 90° between the C-axis and incident polarization. The maximum modification threshold was observed with the polarization oriented at 60° to the C-axis. The pulse energy threshold is minimized to 33% of the maximum at 0° angle, when the laser polarization, crystal C-axis and write-direction are parallel.