Laser spark ignition: experimental determination of laser-induced breakdown thresholds of combustion gases

Phuoc, Tran X.

doi:10.1016/s0030-4018(00)00488-0

Cited by 207 publications

(88 citation statements)

References 11 publications

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“…Our results are consistent with reported values of gas and plasma breakdown, which indicate that the flame lens would have a damage threshold approximately three orders of magnitude higher than conventional coated optics 17 . Indeed, a proposal to circumvent optical damage in highirradiance amplifying systems has recently been mooted: to replace metre-scale beams with millimetre-diameter plasmas through Raman amplification 23 .…”

Section: Discussionsupporting

confidence: 92%

“…Optical devices based on gases and flames have the advantage of a high damage threshold. Although conventional lenses are susceptible to optical damage, a known limitation in advancement of high-power laser systems in the petawatt regimes and beyond, gases and plasmas have very high breakdown thresholds 17 of the order of 10 13 W cm À 2 and 10 17 W cm À 2 , respectively, and thus flames offer several orders of magnitude increase in damage threshold over conventional solid-state optical components, which damages at levels of 10 9 W cm À 2 for coated elements and 10 12 W cm À 2 for polished substrates 18,19 . To date, no studies have taken this concept further to create high damage threshold lens.…”

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confidence: 99%

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Focusing light with a flame lens

et al. 2013

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The lens is a well-understood optical component used for focusing light, but is almost exclusively made in the solid-state form and, thus, suffers from optical damage at high powers. Attempts to overcome this through the use of non-solid graded-index media for lensing, for example, heated gasses, have found limited application owing to their long focal lengths. Here we describe the first flame lens, which produces a sharp focus with very little stray light and has a fourfold increase in focal power per unit length over previous gas lenses. Such gas devices remain topical due to their inherent ability to deliver high-power laser beams: our flame lens has a 'damage' threshold that is several orders of magnitude higher than that of most conventional lenses and is immediately repaired after damage for reuse, and thus will be of use in focusing high-irradiance laser beams.

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Section: Discussionsupporting

confidence: 92%

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confidence: 99%

Focusing light with a flame lens

et al. 2013

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“…Breakdown thresholds of solids and liquids are usually lower than for gases. Several LIB threshold measurements have been reported for oxygen [22][23][24][25][26][27] using CO 2 [22] and Nd : YAG [23][24][25][26][27] lasers. The breakdown threshold was defined as the laser energy at which the gas would break down on more than 50% of the laser shots.…”

Section: Optical Breakdown Threshold Intensities For Omentioning

confidence: 99%

“…In the experimental section we explain the two methods that have been used to measure the breakdown threshold of oxygen. Some authors induce the breakdown at a pressure over the desired value, later the pressure is lowered and the energy adjusted until the breakdown begins with some probability, usually around 50% [26,27]. This method is similar to inducing the breakdown with energy in excess and to attenuating the laser until the spark disappears.…”

Section: Optical Breakdown Threshold Intensities For Omentioning

confidence: 99%

Optical emission spectroscopy of oxygen plasma induced by IR CO₂pulsed laser

Camacho

Santos

Díaz

et al. 2008

J. Phys. D: Appl. Phys.

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Laser-induced breakdown (LIB) spectroscopy in oxygen at room temperature and pressures ranging from 4.6 to 75 kPa was studied using a high-power transverse excitation atmospheric CO 2 laser (λ = 9.621 and 10.591 µm; τ FWHM = 64 ns; power densities ranging from 0.87 to 6.31 GW cm −2 ). The spectrum of the generated plasma is dominated by emission of strong O, O + and weak O 2+ atomic lines. Excitation temperatures of 31 500 ± 1600 K and 23 000 ± 3000 K were estimated by means of O 2+ and O + ionic lines, respectively. Electron number densities of the order of (3.5-16.5) × 10 16 cm −3 were deduced from the Stark broadening of several ionic O + lines. The characteristics of the spectral emission intensities from different species have been investigated as functions of the oxygen pressure and laser irradiance. Optical breakdown threshold intensities in O 2 at 10.591 µm have been determined. The physical processes leading to LIB of oxygen have been analysed.

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“…It is reported that the degree by which the threshold depends on pressure was found to be stronger at a shorter wavelength. 13 Most of the experiments related to laser-induced gas breakdown studies have centered largely on the measurements of breakdown threshold, while little effort has been devoted to the study of energy absorption and propagation in a spark. The present investigation is designed to study the interaction of a focused laser pulse with argon and subsequent energy propagation through the spark medium.…”

Section: Introductionmentioning

confidence: 99%

Laser propagation and energy absorption by an argon spark

Bindhu

Harilal

Tillack

et al. 2003

Journal of Applied Physics

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The laser propagation and energy absorption of an argon spark induced by a laser at different pressures is investigated. 8 ns pulses from a frequency-doubled Q-switched Nd:YAG laser are used to create the spark. The pressure of the argon is varied from 1 atm to 10 Torr. Significant energy absorption by the plasma is observed at high pressures (Ͼ100 Torr) while there is negligible absorption when the pressure is lower than 50 Torr. The plasma kernel showed distinct behavior with respect to laser energy. At a laser energy well above the breakdown threshold, the spark moved only in the backward direction and the forward component was absent indicating the strong absorption of the laser by the spark front. A spiky behavior is observed in the transmitted temporal profiles of the laser at higher energies and at high pressures and can be due to the formation of a self-regulating regime.

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Laser spark ignition: experimental determination of laser-induced breakdown thresholds of combustion gases

Cited by 207 publications

References 11 publications

Focusing light with a flame lens

Focusing light with a flame lens

Optical emission spectroscopy of oxygen plasma induced by IR CO₂pulsed laser

Laser propagation and energy absorption by an argon spark

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Laser spark ignition: experimental determination of laser-induced breakdown thresholds of combustion gases

Cited by 207 publications

References 11 publications

Focusing light with a flame lens

Focusing light with a flame lens

Optical emission spectroscopy of oxygen plasma induced by IR CO2pulsed laser

Laser propagation and energy absorption by an argon spark

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Optical emission spectroscopy of oxygen plasma induced by IR CO₂pulsed laser