<title>High-beam quality and high-average-power industrial CO<formula><inf><roman>2</roman></inf></formula> lasers</title>

Abstract

High power and high beam quality cw carbon-dioxide lasers using new resonators with a phase-unifying output coupler are presented. The phase-unifying output coupler has a circular partial-reflection region in the center surrounded by an antireflection region. The two laser beams that fall onto the two regions of the phase-unifying output coupler have a phase difference from each other when they pass through these regions. The phase difference is structurally canceled out by introducing a stepwise groove outside the phase-unifying output coupler. The new resonators operate in a large volume fundamental mode that is mainly determined by the phase-unifying output coupler. A 5 kW diffraction limited output beam that is promising for industrial laser application is obtained experimentally when the new resonators are applied to high power cw carbon-dioxide lasers. In laser materials processing, we can achieve a penetration depth of 5 mm at a speed of 5 m/min for high speed laser welding of stainless steel. Furthermore, we can cut 1 mm thick mild steel at a speed of 58 m/min and 0.5 mm thick mild steel at a speed of 95 m/min for high speed laser cutting.