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Proceedings Paper

Mid-infrared imaging Fourier transform spectrometry for high power fiber laser irradiated fiberglass composites
Author(s): R. I. Acosta; K. C. Gross; G. P. Perram
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Paper Abstract

New measurement techniques to study continuous wave (CW) laser-material interactions are emerging with the ability to monitor the evolving, spatial distribution of the state of the surface-gas boundary layer. A qualitative analysis of gas phase combustion plumes above the surface of laser irradiated fiberglass composites is developed from fast framing hyperspectral imagery observations. An imaging Fourier Transform Spectrometer (IFTS) operating in the mid-infrared (MWIR) with high framing rate has recently been developed at the Air Force Institute of Technology (AFIT) in collaboration with Telops Inc. A 320 x 256 indium antimonide (InSb) focal plane array with spectral response from 1.5 - 5.5 μm is mated with a Michelson interferometer to achieve spectral resolutions as high as 0.25 cm-1. The very fast 16- tap InSb array frames at 1.9 kHz for the full 320 x 256 frame size. The single pixel field of view of 0.3 mrad provides a spatial resolution of 1 mm at the minimum focal distance of 3 m. Painted and unpainted fiberglass composites are irradiated with a 1064 nm CW Nd:YAG laser for 60 s at 100 W in air at atmospheric pressure. Selective emission in the region of 2100 - 3200 cm-1 is readily evident and is used to develop a time-dependent spatial map of both temperature and plume constituents. The time evolution of gas phase combustion products such as CO and CO2 molecules are monitored, with a spectral resolution of 2 cm-1. High-speed imagery is obtained using a low-pass filter for the interferograms, illustrating significant turbulent behavior during laser irradiation. Spatial brightness temperature maps exceed 600 K. Spatial variation in the ratio of [CO2]/[CO] indicates an interplay between heterogeneous and homogeneous kinetics.

Paper Details

Date Published: 6 February 2012
PDF: 9 pages
Proc. SPIE 8239, High Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications, 82390R (6 February 2012); doi: 10.1117/12.906434
Show Author Affiliations
R. I. Acosta, Air Force Institute of Technology (United States)
K. C. Gross, Air Force Institute of Technology (United States)
G. P. Perram, Air Force Institute of Technology (United States)

Published in SPIE Proceedings Vol. 8239:
High Power Laser Materials Processing: Lasers, Beam Delivery, Diagnostics, and Applications
Eckhard Beyer; Timothy Morris, Editor(s)

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