Study of frequency stabilization for electro-optical Q-switched radio-frequency-excited waveguide CO2 laser using build-up time method.

An electro-optical Q-switched RF-excited Z-fold CO(2) waveguide laser was designed, which can output a Q-switched laser and a cavity-dumped laser synchronously. The build-up time method is presented to stabilize the laser frequency. A closed-loop control system was designed to keep the laser oscillating at the peak of the gain curve by measuring the pulse build-up time continuously and controlling the cavity length. In the experiment, the variations for the pulse build-up time and cavity-dumped laser output power with time were recorded in a period of time. The frequency fluctuation is less than ±16 MHz.

Active and passive frequency stabilization for a Q-switched Z-fold radio-frequency-excited waveguide CO2 laser with two channels.

We report on passive offset frequency stability in free-running applications and active offset frequency stability achieved by use of a frequency-locking technique for a Q-switched Z-fold rf-excited waveguide CO2 laser with two channels. The laser structure of common electrodes and two channels has the advantage of compensating for the frequency variation caused by variations in temperature, cavity length, gas refractive index, and mechanical vibrations, so its offset frequency stability is higher than that of two separate lasers. In the experiments, the offset frequency shift was less than 6 MHz for 3 min in free-running mode. The technique of active offset frequency locking by counting was also introduced. The beat frequency shifting value was smaller than +/- 0.5 MHz in the long-term.