Abstract
The air and thin film plasma(
AP and TFP) sparks may be generated at the same time when high energy laser acts on the
surface of the thin film. AP sparks and TFP sparks are often misjudged when the plasma sparks of laser induced thin film
damage is detected. Measuring the flash ignitio n time (referred to as “spark time” or “ST”) of AP enables researchers to
accurately distinguish AP and TFP sparks and eliminate film damage discrimination that occurs when using plasma flash
methods. A Nd:YAG nanosecond pulse laser with 1064 nm wavelength was employed to generate AP and AP sparks
through induced laser breakdown in air. The incident laser and AP spark signals were collected using high speed free space
detectors and processed using an oscilloscope. These signals were computed and analyzed to obtain the ST of the AP
sparks produced during laser induced breakdown and observe the variations in ST with different laser intensities. Finally, the
multiphoton absorption and cascade ionization theories were applied to calculate and compare theoretical STs to the
experiment results. Findings showed that the experimental STs decreased slightly with an increase in laser intensity.
Moreover, the experimental STs were extremely consistent with the theoretical STs, verifying the feasibility of the proposed
e xperiment method..
Keywords
L aser induced breakdown A ir p lasmas T hin films P lasma sparks.
Citation
GUIXIA WANG, JUNHONG SU, JUNQI XU, QINGSONG WANG, Study of the flash ignition time of air plasma formed through laser induced breakdown, Optoelectronics and Advanced Materials - Rapid Communications, 12, 7-8, July-August 2018, pp.394-400 (2018).
Submitted at: Feb. 2, 2019
Accepted at: Aug. 9, 2018