High power single-longitudinal-mode CO₂ laser with a frequency-tunable range of 0.29 GHz

A frequency-tunable and single-longitudinal-mode master oscillator power amplifier system based on a radio-frequency (RF)-excited waveguide CO₂ laser with three-stage amplification was demonstrated. The continuous tuning range of 0.29 GHz within one longitudinal mode spacing of the RF-excited waveguide CO₂ laser was realized by adjusting the cavity length in closed loop. The linewidth of the CO₂ laser was 3.9 MHz, and the maximal output power was 23.7 W at the center frequency of 9P (20) (9.56 μm). An amplification factor of 17 was obtained by adopting three RF-excited seven-channel folded-waveguide CO₂ amplifiers. This laser system will be a good candidate for coherent detection lidar.