Off-line center operation of an injection-locked single-mode TEA CO2 laser

The possibility of the off-line center operation of an injection-locked single-mode high-power TEA CO2 laser required for the pumping of a submillimeter laser for the collective scattering measurement of tokamak ion temperatures is reported. Rate equations of a homogeneously broadened TEA CO2 laser including the injection term were solved numerically for 21 cavity modes by the use of the Runge-Kutta-Gill method. When the monochromatic radiation is injected 1.5 GHz from the center of the gain curve, it is found that at the initial stage of laser action, the mode coupled with the injected radiation builds up dominantly and the other mode is completely suppressed; at the tail of the pulse, modes with large gain gradually build up, and the emission spectra change into normal multimode operation. As the injected power is increased, the build-up time of the high gain mode is delayed. It is noted that injection-locked operation with the demonstrated tunability can be easily implemented using an etalon-tuned single-mode TEA CO2 laser as an injection source.