Theory of self-oscillation and mode locking in a longitudinal photoacoustic resonator

ORAL

Abstract

The wave equation for pressure that governs generation of the photoacoustic effect possesses a forcing term proportional to the time derivative of the energy delivered to the gas per unit volume and time. A positive pressure fluctuation, with its accompanying density increase, thus increases the optical absorption and provides a positive feedback mechanism for sound generation. A theory for self-oscillation in a one-dimensional resonator is given. Expressions for the photoacoustic pressure are derived for the cases of highly and weakly absorbing gases that indicate mode-locked sound generation. Experiments with CO2 lasers are reported where evidence of the self-generation effect was sought.

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Authors

  • Ziyao Tang

    Brown University

  • Christopher Lane

    College of the Holy Cross, Bridgewater State University, Brown University, Harvard University, University of Tennessee at Chattanooga, Boston College, Istanbul Technical University, Dartmouth College Physics and Radiology, Northeastern University, University of Colorado, Northeastern University, National University of Singapore

  • Christopher Lane

    College of the Holy Cross, Bridgewater State University, Brown University, Harvard University, University of Tennessee at Chattanooga, Boston College, Istanbul Technical University, Dartmouth College Physics and Radiology, Northeastern University, University of Colorado, Northeastern University, National University of Singapore

  • Christopher Lane

    College of the Holy Cross, Bridgewater State University, Brown University, Harvard University, University of Tennessee at Chattanooga, Boston College, Istanbul Technical University, Dartmouth College Physics and Radiology, Northeastern University, University of Colorado, Northeastern University, National University of Singapore