TIME-RESOLVED SHADOWGRAPHIC IMAGING OF THE RESPONSE OF DILUTE SUSPENSIONS TO LASER-PULSES

Time-resolved imagery is presented showing the changes that occur in t he focal volume of dilute liquid-particle suspensions following the ar rival of single, Q-switched, frequency-doubled, Nd:YAG laser pulses. D ata are presented for a carbon particle suspension consisting of used (carbonized) 10W-15 motor oil and for a suspension of the inorganic me tallic cluster molecule Mo2Ag4S8[PPh3](4). The images in conjunction w ith the accompanying limiting data show that the reduction in transmis sion, observed as the input pulse energy is increased, results from sc attering from bubbles augmented by plasma absorption. The imaging tech nique involves converting a portion of the laser pulse to probe pulses that are then delayed through varying lengths of optical fiber. The f ocal volume is probed perpendicular to the incident beam at various ti mes from 12 ns to 2.9 mu s after the arrival of the pulse in the test cell. Light emitted from the cell as a result of incandescence or a ho t plasma is also imaged. Nonlinear loss, time-resolved pump-probe and picosecond limiting experiments, performed at the University of Centra l Florida's Center fur Research in Electro-Optics and Lasers (CREOL), are described in the companion paper in this issue entitled ''Nonlinea r optical properties of the inorganic metal cluster Mo2Ag4S8[PPh3](4). '' (C) 1998 Optical Society of America [S0740-3224(98)00405-6].