Longitudinally excited N 2 laser with large-diameter discharge tube.

To realize an ultraviolet laser with high beam quality and high output power, we are developing a master oscillator power amplifier system for a longitudinally excited gas laser. In this system, high beam quality is produced by an oscillator stage, and high output power is produced by an amplifier stage. Here, the beam profile of the longitudinally excited gas N ₂ laser had a quasi-Gaussian shape when using a large-diameter discharge tube, which enabled the use of the amplifier stage. The discharge tube consisted of a dielectric pipe with an inner diameter of 14 mm and a length of 30 cm. The discharge tube was covered with a metallic tube for pre-ionization. The strength and spatial distribution of pre-ionization were optimized by adjusting the gap between the metallic tube and the discharge tube. The uniform discharge achieved by controlling the pre-ionization produced a quasi-Gaussian laser beam profile with a correlation factor of 0.99513, a laser pulse energy of 343 μJ, and an input energy of 2.95 J.