EVALUATING A FEMTOSECOND LASER-INDUCED BREAKDOWN SPARK AS AN AERO-OPTIC ILLUMINATION SOURCE
EVALUATING A FEMTOSECOND LASER-INDUCED BREAKDOWN SPARK AS AN AERO-OPTIC ILLUMINATION SOURCE
Files
Publication or External Link
Date
2022
Authors
Neisess, Christoph
Advisor
Cadou, Christopher
Citation
DRUM DOI
Abstract
Currently, limitations exist on collecting aero-optic wavefront data in a wind tunnel dueto the types of sources available to illuminate the flow-field for the sensing optics. Collimated
laser sources are commonly used, but are limited by the ability to place hardware to steer the
beam towards the sensing optics. Laser-Induced Breakdown (LIB) sparks have also been tested,
but create additional measurement errors due to variations in their size and position with each
laser pulse. In this work, a new approach using a Femtosecond Laser-Induced Breakdown (FSLIB)
spark is evaluated as a possible solution to the problems faced by nanosecond LIB sparks,
namely the significant amount of spark size and position variation present in the latter. The FSLIB
spark was imaged with a camera in order to study the amount of pulse-to-pulse position
and size change present in its generation. Additionally, the FS-LIB spark was used to collect
aero-optic data in conjunction with a Shack-Hartmann style wavefront sensor on a Mach 2.8
flowfield. The results of this analysis indicated that the FS-LIB spark experiences significantly
less pulse-to-pulse variation in its size and position than a nanosecond LIB spark. In addition,
the wavefront data collected with the FS-LIB spark compared favorably to data collected with a
more conventional collimated laser beam for illumination. This indicates that the FS-LIB spark
is a promising alternative to the use of collimated sources in aero-optic data collection.