Abstract
A high power CO2 laser equipped with an unstable resonator with a phase-unyifying output coupler has been developed to produce a highly focusing laser beam. The output coupler composed of a partial-reflection region in its center sorrounded by an antireflection region unifies the phases of laser beams passing through these regions. A linearly polarized, diffraction limited beam of 5kW with a divergence angle of 0.6mrad can be extracted stably. The laser beam is successfully applied to high speed welding and cutting.
