Design considerations and scaling laws for high power convective cooled CW CO2 lasers

Abstract

Various criteria for designing high power convective cooled CO2 lasers have been discussed. Considering the saturation intensity, optical damage threshold of the optical resonator components and the small-signal gain, the scaling laws for designing high power CW CO2 lasers have been established. In transverse flow CO2 lasers having discharge of square cross-section, the discharge lengthL and its widthW for a specific laser powerP (Watt) and gas flow velocityV (cm/s) can be given byL = 1.4 x 104 p 1/2 V -1 cms andW = 0.04P 1/2 cms. The optimum transmitivity of the output coupler is found to be almost constant (about 60%), independent of the small signal gain and laser power. In fast axial flow CO2 lasers the gas flow should be divided into several discharge tubes to maintain the flow velocity within sonic limit. The discharge length in this type of laser does not depend explicitly on the laser power, instead it depends on the input power density in the discharge and the gas flow velocity. Various considerations for ensuring better laser beam quality are also discussed.