Pulsed CO2laser with double modulation

For the pulse pumped CO2laser we used Q-switching to investigate inversion kinetics. The pump was synchronized with the Q-switching mirror. It was possible to obtain the Q-switch pulses at any phase of the pump pulse. The repetition rate was 50 Hz and the pump pulse duration was 4 or 10 ms. It was found that there is an optimum delay in switching the cavity Q-factor after the discharge started. The giant pulse intensity increased several times after the discharge was switched from CW to pulses. The inversion rise time was 1-2 ms and its lifetime was strongly dependent on the discharge current, due to plasma heating during the current pulse. Increasing the helium percentage in the discharge prolonged the inversion lifetime because of high thermal conductivity of helium gas. Gaseous BCl3was chosen to obtain the CO2laser giant pulses with bleachable filter. The vibronic frequency V3of the B¹¹Cl3molecules coincides with the lines of the CO2laser. Rarer B¹⁰Cl3corresponds to less active lines. Pure BCl3did not give the giant pulses. Adding helium to the BCl3cell gave the pulses. The best results came from adding very small amounts of ammonia NH3because of the effective vibrational energy transfer between colliding BCl3and NH3molecules.