Active attenuation of acoustic disturbances in high energy pulsed lasers

Abstract

The potential advantages of the active attenuation of acoustic disturbances in high energy pulsed lasers have been analyzed, using the theory developed for the control of sound in long ducts [M. A. Swinbanks, J. Sound Vib. 27, 411–436 (1973)]. The results show that active attenuators, which are especially effective at the lower audio frequencies, could be used in conjunction with passive mufflers to significantly reduce the total muffler volume required to damp the acoustic disturbances to an acceptable level. Only modest acoustical power would be required because the active attenuation system would be used to damp just the fraction of the acoustical disturbance which is reflected back toward the optical cavity by the thermal interface created by the previous laser pulse. The additional attenuation provided by an active system could also result in higher laser pulse rates, and thus higher average power. The design requirements for an experimental demonstration of the potential benefits of active attenuation for pulsed laser operation will also be discussed.