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Single-shot, spatially-resolved stand-off detection of atomic hydrogen via backward lasing in flames

Ruchkina, Maria LU ; Ding, Pengji LU ; Ehn, Andreas LU ; Aldén, Marcus LU and Bood, Joakim LU (2019) In Proceedings of the Combustion Institute 37(2). p.1281-1288
Abstract

We report on an experimental demonstration of spatially-resolved detection of atomic hydrogen in flames using a single-ended configuration yielding 656-nm lasing in the backward direction upon 2-photon pumping with 205-nm femtosecond laser pulses. Spatial resolution is achieved by temporally-resolved detection of the backward lasing using a streak camera. The method is demonstrated in CH4/O2 flames; both in a setup consisting of two flames, with variable spacing between the flames, and in a single flame. Results from the two-flame experiment show that the backward lasing technique is able to determine changes in the separation between the flames as this distance was altered. By maximizing the temporal resolution of... (More)

We report on an experimental demonstration of spatially-resolved detection of atomic hydrogen in flames using a single-ended configuration yielding 656-nm lasing in the backward direction upon 2-photon pumping with 205-nm femtosecond laser pulses. Spatial resolution is achieved by temporally-resolved detection of the backward lasing using a streak camera. The method is demonstrated in CH4/O2 flames; both in a setup consisting of two flames, with variable spacing between the flames, and in a single flame. Results from the two-flame experiment show that the backward lasing technique is able to determine changes in the separation between the flames as this distance was altered. By maximizing the temporal resolution of the streak camera, obtaining a highest spatial resolution of 1.65 mm, it is possible to resolve the hydrogen signal present in the two reaction zones in the single flame, where the separation between the reaction zones is ~2 mm. The lasing signal is strong enough to allow single-shot measurements. Results obtained by backward lasing are compared with 2-photon planar laser-induced fluorescence (LIF) images recorded with detection perpendicular to the laser beam path and the results from the two methods qualitatively agree. Although further studies are needed in order to extract quantitative hydrogen concentrations, the present results indicate great potential for spatially resolved single-ended measurements, which would constitute a very valuable asset for combustion diagnostics in intractable geometries with limited optical access. It appears feasible to extend the technique to detection of any species for which resonant two-photon-excited lasing effect has been observed, such as O, N, C, CO and NH3.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Backward lasing technique, Combustion diagnostics, Hydrogen atom, Multiphoton processes, Ultrashort nonlinear optics
in
Proceedings of the Combustion Institute
volume
37
issue
2
pages
1281 - 1288
publisher
Elsevier
external identifiers
  • scopus:85051203895
ISSN
1540-7489
DOI
10.1016/j.proci.2018.06.145
language
English
LU publication?
yes
id
edd5a48c-0878-43b7-9fc7-d0b4541de5d0
date added to LUP
2018-09-12 14:02:21
date last changed
2019-09-17 04:38:23
@article{edd5a48c-0878-43b7-9fc7-d0b4541de5d0,
  abstract     = {<p>We report on an experimental demonstration of spatially-resolved detection of atomic hydrogen in flames using a single-ended configuration yielding 656-nm lasing in the backward direction upon 2-photon pumping with 205-nm femtosecond laser pulses. Spatial resolution is achieved by temporally-resolved detection of the backward lasing using a streak camera. The method is demonstrated in CH<sub>4</sub>/O<sub>2</sub> flames; both in a setup consisting of two flames, with variable spacing between the flames, and in a single flame. Results from the two-flame experiment show that the backward lasing technique is able to determine changes in the separation between the flames as this distance was altered. By maximizing the temporal resolution of the streak camera, obtaining a highest spatial resolution of 1.65 mm, it is possible to resolve the hydrogen signal present in the two reaction zones in the single flame, where the separation between the reaction zones is ~2 mm. The lasing signal is strong enough to allow single-shot measurements. Results obtained by backward lasing are compared with 2-photon planar laser-induced fluorescence (LIF) images recorded with detection perpendicular to the laser beam path and the results from the two methods qualitatively agree. Although further studies are needed in order to extract quantitative hydrogen concentrations, the present results indicate great potential for spatially resolved single-ended measurements, which would constitute a very valuable asset for combustion diagnostics in intractable geometries with limited optical access. It appears feasible to extend the technique to detection of any species for which resonant two-photon-excited lasing effect has been observed, such as O, N, C, CO and NH<sub>3</sub>.</p>},
  author       = {Ruchkina, Maria and Ding, Pengji and Ehn, Andreas and Aldén, Marcus and Bood, Joakim},
  issn         = {1540-7489},
  keyword      = {Backward lasing technique,Combustion diagnostics,Hydrogen atom,Multiphoton processes,Ultrashort nonlinear optics},
  language     = {eng},
  number       = {2},
  pages        = {1281--1288},
  publisher    = {Elsevier},
  series       = {Proceedings of the Combustion Institute},
  title        = {Single-shot, spatially-resolved stand-off detection of atomic hydrogen via backward lasing in flames},
  url          = {http://dx.doi.org/10.1016/j.proci.2018.06.145},
  volume       = {37},
  year         = {2019},
}