High-power CO2 laser using Gauss-core resonator for 6-kW large-volume TEM00 mode operation

A novel resonator based on a stable resonator configuration designed to yield a highly focusing beam operating in a large-volume TEM ₀₀ is presented. An output coupler of the new stable resonator has a circular partial-reflection region in the center that is surrounded by an antireflection region. Main-beam mode is determined by the partial-reflection region existing in the “core” of the output coupler. A diffraction beam spread from the center of the optical path in the cavity is amplified by a laser medium. By combining part of the core beam transmitted from the partial-reflection region with the amplified diffraction beam under the phase-unified condition, a diffraction-limited laser beam having a large diameter is obtained. A 6.2-kW linearly polarized output beam with the M² factor of 1.7 is obtained experimentally for a high-power CW CO₂ laser. In laser-materials processing, we can cut 1:mm thin mild steel with a cutting speed as high as 64 m/min, at 5.9 kW