Application of mid-infrared tuneable diode laser absorption spectroscopy to plasma diagnostics: a review

Röpcke, J.; Lombardi, G.; Rousseau, Antoine; Davies, Paul

doi:10.1088/0963-0252/15/4/s02

Cited by 101 publications

(95 citation statements)

References 123 publications

(217 reference statements)

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“…ERSiCOH (nm·s −1 ) = 4.64 × 10 13 [SiF4] − 1.18 (1) where [SiF4] is given in units of 10 13 molecules cm −3 , see Figure 17. Therefore, the concentration of the etching products can be directly used as a measure of the etching rate.…”

Section: Industrial Process Monitoring In Low-pressure Plasmasmentioning

confidence: 99%

“…Over the last two decades, chemical sensing using mid infrared laser absorption spectroscopy (MIR-LAS) in the molecular fingerprint region from 3 to 20 µm, which contains strong ro-vibrational absorption bands of a large variety of gaseous species, has been established as a powerful in situ diagnostic tool for molecular plasmas [1][2][3][4][5][6]. Quantum cascade lasers (QCL) in particular have played a central role in this field so much so that they have become the infrared light sources of choice for plasma diagnostics in the mid infrared.…”

Section: Introductionmentioning

confidence: 99%

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Applying Quantum Cascade Laser Spectroscopy in Plasma Diagnostics

et al. 2016

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Abstract:The considerably higher power and wider frequency coverage available from quantum cascade lasers (QCLs) in comparison to lead salt diode lasers has led to substantial advances when QCLs are used in pure and applied infrared spectroscopy. Furthermore, they can be used in both pulsed and continuous wave (cw) operation, opening up new possibilities in quantitative time resolved applications in plasmas both in the laboratory and in industry as shown in this article. However, in order to determine absolute concentrations accurately using pulsed QCLs, careful attention has to be paid to features like power saturation phenomena. Hence, we begin with a discussion of the non-linear effects which must be considered when using short or long pulse mode operation. More recently, cw QCLs have been introduced which have the advantage of higher power, better spectral resolution and lower fluctuations in light intensity compared to pulsed devices. They have proved particularly useful in sensing applications in plasmas when very low concentrations have to be monitored. Finally, the use of cw external cavity QCLs (EC-QCLs) for multi species detection is described, using a diagnostics study of a methane/nitrogen plasma as an example. The wide frequency coverage of this type of QCL laser, which is significantly broader than from a distributed feedback QCL (DFB-QCL), is a substantial advantage for multi species detection. Therefore, cw EC-QCLs are state of the art devices and have enormous potential for future plasma diagnostic studies.

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Section: Industrial Process Monitoring In Low-pressure Plasmasmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Applying Quantum Cascade Laser Spectroscopy in Plasma Diagnostics

et al. 2016

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“…Radicals containing carbon and oxygen are of special interest for fundamental studies and for applications in plasma technology. Although hydrogen and hydrocarbon containing plasmas with admixtures of oxygen and nitrogen have been extensively studied [1,20] there is still a lack of experimental data concerning the absolute densities of radicals in these discharges. The hydroxyl radical is known to be one of the main oxidising radicals.…”

Section: General Considerationsmentioning

confidence: 99%

“…The absorption cross sections of SiF 4 and NF 3 have been determined to be molecule The quantum cascade laser system Q-MACS Etch consists of a pulsed infrared QCL source with the laser wavelength tuneable in the range 1027 -1032 cm -1 , optical components, detectors and data acquisition cards controlled by a PC. The laser driver used was a Q-MACS Basic [1,52]. The Q- MACS Basic provides a laser pulse width tuneable between 10 -255 ns and a repetition frequency between 100 Hz -1 MHz.…”

Section: Plasma Diagnostics With High Time Resolutionmentioning

confidence: 99%

Kinetic and Diagnostic Studies of Molecular Plasmas Using Laser Absorption Techniques

Röpcke

Engeln

Schram

et al. 2010

Introduction to Complex Plasmas

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Abstract. Within the last decade mid infrared absorption spectroscopy between 3 and 20 µm, known as Infrared Laser Absorption Spectroscopy (IRLAS) and based on tuneable semiconductor lasers, namely lead salt diode lasers, often called tuneable diode lasers (TDL), and quantum cascade lasers (QCL) has progressed considerably as a powerful diagnostic technique for in situ studies of the fundamental physics and chemistry of molecular plasmas. The increasing interest in processing plasmas containing hydrocarbons, fluorocarbons, organosilicon and boron compounds has lead to further applications of IRLAS because most of these compounds and their decomposition products are infrared active. IRLAS provides a means of determining the absolute concentrations of the ground states of stable and transient molecular species, which is of particular importance for the investigation of reaction kinetics. Information about gas temperature and population densities can also be derived from IRLAS measurements. A variety of free radicals and molecular ions have been detected, especially using TDLs. Since plasmas with molecular feed gases are used in many applications such as thin film deposition, semiconductor processing, surface activation and cleaning, and materials and waste treatment, this has stimulated the adaptation of infrared spectroscopic techniques to industrial requirements. The recent development of QCLs offers an attractive new option for the monitoring and control of industrial plasma processes as well as for highly time-resolved studies on the kinetics of plasma processes. The aim of the present article is threefold: (i) to review recent achievements in our understanding of molecular phenomena in plasmas, (ii) to report on selected studies of the spectroscopic properties and kinetic behaviour of radicals, and (iii) to describe the current status of advanced instrumentation for TDLAS in the mid infrared.

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“…Tunable diode laser absorption spectroscopy, TDLAS, using such lasers is a powerful and widely used technique for gas sensing applications including environmental monitoring, chemical analysis, plasma spectroscopy and combustion diagnostics [1][2][3]. The use of wavelengths in the spectral range 4-10 μm is advantageous since many important molecular species exhibit strong well-resolved absorption features in this range.…”

Section: Introductionmentioning

confidence: 99%

Multi-mode absorption spectroscopy using a quantum cascade laser for simultaneous detection of NO and H2O

et al. 2016

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cascade lasers, QCLs. The high resolution available using single-mode devices provides high sensitivity with minimum detection limits in the range of ppbv in some applications. The limited range of mode-hop-free, MHF, tuning of most single-mode lasers, however, often restricts TDLAS methods to detection of a single species unless, fortuitously, two species have transitions lying within the MHF range. Detection of more than one species using TDLAS usually involves multiplexing several lasers and detector systems [4]. Widely tunable external cavity diode lasers, emitting narrow line or single-mode outputs, have recently been demonstrated in the 4-10 μm mid-infrared range based on quantum cascade devices but the relatively slow tuning rates limit application in rapidly changing environments [5]. A variety of broadband spectroscopy methods have been developed that allow detection of multiple species over a wide spectral range but not all are available in the mid-IR. These include use of multi-section diodes, broadband or wavelength agile light sources and correlation spectroscopic methods [6][7][8][9][10][11][12]. The wide bandwidth "frequency combs" available from mode-locked lasers has been exploited for broadband spectroscopy but usually involve complex laser systems and high resolution dispersion optics [13,14]. Extension of comb-based spectroscopy to the mid-infrared beyond 4 μm is becoming possible with the development of frequency combs based on QCL devices. A comb of width 100 cm −1 has recently been demonstrated at 7 μm [15]. Heterodyne methods, with potential for multi-species sensing, have also been demonstrated to allow detection in the RF region at the cost of some additional complexity and restriction in width of the spectrum covered [16].The technique of multi-mode absorption spectroscopy, MUMAS, addresses some of the limitations of TDLAS, specifically by providing wide spectral coverage whilst Abstract Detection of multiple transitions in NO and H 2 O using multi-mode absorption spectroscopy, MUMAS, with a quantum cascade laser, QCL, operating at 5.3 μm at scan rates up to 10 kHz is reported. The linewidth of longitudinal modes of the QCL is derived from pressure-dependent fits to experimental MUMAS data. Variations in the spectral structure of the broadband, multi-mode, output of the commercially available QCL employed are analysed to provide accurate fits of modelled MUMAS signatures to the experimental data.

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Application of mid-infrared tuneable diode laser absorption spectroscopy to plasma diagnostics: a review

Cited by 101 publications

References 123 publications

Applying Quantum Cascade Laser Spectroscopy in Plasma Diagnostics

Applying Quantum Cascade Laser Spectroscopy in Plasma Diagnostics

Kinetic and Diagnostic Studies of Molecular Plasmas Using Laser Absorption Techniques

Multi-mode absorption spectroscopy using a quantum cascade laser for simultaneous detection of NO and H2O

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