Breakdown thresholds of picosecond optical pulses and nanosecond pulsed electric fields

摘要

We investigate the effect of nanosecond pulsed electric fields on optical breakdown thresholds for picosecond opticalpulses (6ps pulse duration at wavelength of 1064nm) in aqueous solutions. Optical breakdown thresholds are determinedboth with and without the application of the nanosecond pulsed electric fields in water, phosphate-buffered salinesolution, and a typical buffer solution used for live cell imaging. As optical breakdown at this time-scale mostly on acombination of multi-photon ionization as well as free electrons in the focal volume to achieve an avalanche or cascadeionization phenomena, we hypothesize that the application of a strong external electric field will have a significantimpact on the breakdown probability at the lower-end of pulse energy levels, effectively modifying the pulse-energybreakdown threshold of the materials. Single optical pulses were triggered at specific times with respect to the leadingedgeof the applied electric field to determine if there were any time-dependent effects on breakdown thresholds. Resultsof the experiments are examined and the physical phenomena as well as the concept “electrostatic purification” arediscussed.