A gas cell filled with argon gas under pressure is placed in a tightly focused laser beam to provide a limiter for laser pulses above a certain peak power, corresponding to the optical breakdown threshold for the creation of a laser-induced plasma. Measurements of the threshold intensity as a function of argon gas pressure are given for a laser wavelength of 1.064 μm (Nd:YAG) and a pulse length of 6.4 ns. Threshold intensities for optical breakdown in fused silica were measured with the same optical system, enabling a relative comparison of breakdown thresholds, of interest for protecting fused-silica optical components in fiber-optic delivery systems for laser material processing applications. The threshold intensity was measured to 220 GW/cm<sup>2</sup> in Ar at 1.0 × 10<sup>5</sup> N/m<sup>2</sup> (1 atm), 80 GW/cm<sup>2</sup> in Ar at 8.0 × 10<sup>5</sup> N/m<sup>2</sup> (7.9 atm), and 55 GW/cm<sup>2</sup> in fused silica. Even though the threshold in argon is higher than that in fused silica, the limiter will protect the optical components if the laser beam is focused to a tighter spot in the gas cell than at the input end of the fiber.
© 2003 Optical Society of America
Sheila Galt, Mats Sjöberg, Manuel Lopez Quiroga-Teixeiro, and Sverker Hård, "Optical Breakdown in Fused Silica and Argon Gas: Application to Nd:YAG Laser Limiter," Appl. Opt. 42, 579-584 (2003)