Event
Ph.D. Research Proposal Exam: Andrew Goffin
Tuesday, August 9, 2022
2:00 p.m.
ERF1207
Emily Irwin
301 405 0680
eirwin@umd.edu
ANNOUNCEMENT: Ph.D. Research Proposal Exam
Name: Andrew Goffin
Committee:
Professor Milchberg (Chair)
Professor Goldhar
Professor Davis
Date/time: Tuesday August 9th, 2:00pm
Location: ERF1207 (Large Conference Room)
Title: Atmospheric Aerosol Clearing by Femtosecond Filaments
Abstract:
Atmospheric aerosols, such as water droplets in fog, interfere with laser propagation through scattering and absorption. Femtosecond optical filaments have been shown to clear foggy regions, improving transmission of subsequent pulses. However, the detailed fog clearing mechanism had yet to be determined. Here we directly measure and simulate the dynamics of ~5 µm radius water droplets, typical of fog, under the influence of optical and acoustic interactions characteristic of femtosecond filaments. We find that for filaments generated by the collapse of collimated near-infrared femtosecond pulses, the main droplet clearing mechanism is optical shattering by laser light. For such filaments, the single cycle acoustic wave launched by filament energy deposition in air leaves droplets intact and drives negligible transverse displacement, and therefore negligible fog clearing. Only for tightly focused non-filamentary pulses, where local energy deposition greatly exceeds that of a filament, do acoustic waves significantly displace aerosols. Future work will adjust filament parameters, such as pulse duration, in an attempt to increase local energy deposition over long propagation distances and potentially drive significant acoustic aerosol clearing.
