Acoustic Waves Excited byQ-Switched CO2Laser

In the course of measurements of a discharge current in a CO2 laser tube, current oscillations of about 20 kHz were observed just after a Q-switched laser pulse emission. The current oscillations were also found, when the Q-switched laser pulse was incident on discharged plasmas of CO2 or N2. The observed frequencies were 9 kHz in CO2 plasma and 13 kHz in N2 plasma, when a discharge tube of inner diameter of 43 mm was used. Theoretical analysis shows that an acoustic wave excited by the laser pulse gives rise to the current oscillation which we observed.