Theory and experiments on the power modulation of CO2 lasers

The operation of a pulsed transverse flow CO₂ laser system with RF excitation is studied theoretically by computer simulation. The calculations are supported by experimental results which confirm that the pulse repetition frequency of the system is restricted by the time delay between the electric and the laser pulse and by relaxation oscillations. The time delay is roughly inversely proportional to the gas pressure and not very sensitive to variations of the CO₂ fraction and the output coupling of laser radiation. A pulse repetition frequency over some 30 kHz can be attained only if the excitation pulse period is equal to the delay time, but this operation condition is very sensitive to changes of the duty cycle. The calculations show that full modulation depth should be attainable up to a repetition frequency of 360 kHz