Theory of self-oscillation and mode locking in a longitudinal photoacoustic resonator.
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.
Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
Ziyao
Z
Tang
Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
Han Jung
HJ
Park
Department of Engineering and Applied Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
Roger M
RM
Diebold
Department of Chemistry, Brown University, Providence, Rhode Island 02912, USA.
Gerald J
GJ
Diebold