Bulk damage growth characteristics and ultrafast diagnosis of fluoride-containing phosphate glasses induced by 355-nm laser

Abstract

To comprehensively reveal the influence regularity of different glass melting temperatures on the ultraviolet (UV) laser-induced damage resistance of fluoride-containing phosphate glasses, the initial bulk damage, damaged growth, and dynamic behaviors of both fundamental-frequency (1ω) absorptive and third-harmonic-frequency (3ω) transparent fluoride-containing phosphate glasses are explored utilizing the time-resolved pump–probe shadowgraph technique. A low-temperature (1000 °C) glass melting process resulted in an increase in the absorption coefficient at 355 nm and decrease in the optical bandgap for the 1ω absorptive glass. The produced 1ω absorptive glass was subjected to higher shock pressure and shock temperature on the rear surface after a single-pulse laser irradiation, and had a more serious filamentation damage accompanied by a funnel-shape morphology. With the subsequent multiples irradiation, the initial bulk damage area increased exponentially with a growth coefficient of 0.72. The corresponding exponential growth coefficient for the counterpart 1ω absorptive glass melted at a high temperature (1200 °C) was only 0.32 due to its slight initial bulk damage. In contrast, for the 3ω transparent glass, the high-temperature (1200 °C) melting process led to a larger initial bulk damage area and largest exponential growth coefficient of 0.91, 1.1 times that of the 3ω transparent glass melted at a low temperature (1000 °C). They exhibited wave-packed damaged morphologies extending from the rear surface into the glass body. The melting temperatures exhibited the opposite influence regularity for these two investigated fluoride-containing phosphate glasses. The high-temperature (1200 °C) melting process favored the improvement in UV laser-induced damage resistance of the 1ω absorptive glass, as evidenced by the higher UV laser-induced damage threshold and lower damage growth coefficient, while the low-temperature (1000 °C) melting process exerted similar effects on the 3ω transparent glass.