It is shown that a longitudinal CO2 laser with two discharge tubes electrically coupled in parallel can be operated in pulsed mode without ballast impedance. This scheme not only yields much higher efficiency (up to 13% at the maximum output energy) and eliminates component failure at high pulse repetition frequency (prf) but also facilitates short pulse availability. In the absence of ballast, current and laser pulse width decrease on increasing the voltage applied to the discharge tubes but these quantities remain unaffected on varying the value of the energy storage capacitor. This enables an independent control of the laser pulse duration and energy. Threshold energy for the onset of nonuniformities in the glow discharge reduces almost exponentially on increasing the discharge current pulse duration but rises on decreasing the operating value of E/N, the electric field to neutral gas density ratio. The maximum output laser energy of about 1 J/pulse, adjustable pulse duration from 30 μs to about 2 ms, and prf up to 50 Hz have been obtained.

Articles you may be interested inLongitudinal mode selection in hybrid CO2 laser for subthreshold operation of cw discharge section

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It is found that a long conventional CW CO2 laser cannot be tuned selectively because of the multidirectional modes formed through reflections at grazing angles from the inner walls of the discharge tubes. This problem has been overcome by inserting a number of properly designed mode-selecting apertures right into the discharge tubes and selective tuning over more than 150 rotational lines in both P and R branches of three vibrational bands (9.6, 10.6 and 11.2 mu m) has been achieved. The rotational lines of higher J-values that have a low gain tend to lase in the TEM10 mode. In the R branch two consecutive lines are observed to lase simultaneously when the angular width of the active medium subtended at the grating allows the existence of two physically tilted beams of different wavelengths dispersed by the grating used. The output power distribution over various lines almost follows that of the gain. The optimum design parameters of a long CW CO2 laser for tuning are obtained.

Investigation of the effect of laser treatment on the longitudinal and transverse velocity of an aluminum alloy