Stark effect driven Q-switching of the CO2laser

Q-switching of molecular lasers (CO2and N2O) by the use of intracavity saturable absorbers has been achieved on many different lines with a variety of molecular gases. Since this effect is essentially "passive," the pulse frequency is difficult to specify and also subject to the vagaries of fluctuations in cavity length and laser excitation. The application of a suitable combination of DC and time-varying electric fields to an appropriate absorbing gas has enabled us to eliminate this frequency instability and to produce high efficiency driven Q-switching in both the 9.4µ and 10.4µ bands of the CO2laser. By this technique, the absorption cross section is rendered a function of the applied Stark field in addition to its dependence on the incident light intensity. Both pulsed and sinusoidal electric fields have been used to induce Q-switching, with 200 volts being a typical driving voltage. The average power in the Q-switched mode, using this control technique, is as high as 95% of the unmodulated laser output power, and pulse repetitive rates up to 135 KHz have been achieved.