PLASMA INSTABILITY IN HIGH-POWER CO2 LASER AMPLIFIERS

In the present paper a general model of plasma instabilities m high-power e-beam sustained CO2 laser amplifiers is illustrated. This model improves the Nighan-Haas one by allowing explicitly for the various degrees of vibrational freedom and taking into account the stabilizing effect of the laser field intensity. Two numerical codes, which have been used to calculate the steady-state plasma properties needed to carry out the stability analysis, are also presented. The model has been used to test the degree of thermal and ionic instability of an EDCL device using four-component gas mixture (CO2 - N2 - He-CO)

Optical phase conjugation through translational and rotational diffusive rearrangements of liquid-dispersed microparticles

Optical phase conjugation by degenerate four-wave mixing has been achieved in the cw regime in liquid suspensions of polymer microellipsoids. The results clearly show that particle-number-density gratings and orientational gratings are generated within the suspensions over different ranges of the excitation frequency depending upon the beam polarization configuration and the host-liquid viscosity. The measured parameters are in good agreement with a classical model based on light-induced particle diffusive rearrangements. © 1990 The American Physical Society