Special Issue "Laser Spectroscopy and Sensing"

Guest Editor
Prof. Dr. Markus W. Sigrist
ETH Zürich, Institute for Quantum Electronics, HPF D 19, Schafmattstrasse 16, CH-8093 Zürich, Switzerland
Website: http://www.lss.ethz.ch/people/head/markus_sigrist/index
E-Mail:
Interests: widely tunable infrared laser sources; sensitive and selective monitoring methods such as multipass absorption, photoacoustics and cavity ringdown; algorithms for spectral analyses of multi-component mixtures; low-cost photoacoustic gas sensors; application of laser-spectroscopic schemes

The special issue on "Laser Spectroscopy and Sensing" addresses following topics, but is not limited by:

• Laser-based sensors for gases, liquids, and solid
• Requirements: sensitivity, specificity, temporal resolution, in situ, remote, etc.
• Mathematical analysis of multi-component spectra
• UV vis. IR spectroscopy
• Laser sources: tunable diode lasers, VCSELs and VECSELS, interband cascade lasers (ICLs), quantum cascade lasers (QCLs), lead salt diode lasers, nonlinear optical sources (difference frequency generation (DFG), optical parametric oscillators (OPOs), tuning performance, linewidth, etc.
• Interaction of radiation with matter: absorption, scattering, fluorescence Measurements schemes: Multipass and intracavity absorption, photoacoustics, cavity ringdown, etc.
• Application areas:
  • Isotope ratio determination
  • Environment: temporal and spatial distribution of trace gases and particulate matter, urban and rural areas
  • Agriculture and food science: dynamic control of atmosphere in green- and storage houses, surveillance of ripening, wilting and fermentation processes, toxic compounds like melamine, acrylamide, etc.
  • Industry: emission control, workplace safety, process monitoring, etc.

Title: Single Longitudinal Mode Composite Cavity Fibre Laser for Sensor Applications
Authors: Ian Leung, Asrul Izam, Paul Childs, Yunjiang Rao and Gang-Ding Peng
Abstract: In this paper, we report our study on the intensity and spectral characteristics of composite cavity fibre lasers from the perspective of their sensor applications. We also report experimental results from our design, fabrication and characterization of composite cavity fibre lasers. We demonstrated that composite cavity fibre lasers could have desirable coherence characteristics, higher output power and high dynamic sensitivity, making them attractive for various sensor applications.

Title: Surface-Sensitive Raman Spectroscopy for Probing Molecular Layer Systems
Authors: Kiang Wei Kho, Praveen Thoniyot, Malini Olivo
Tentative Abstract: The paper will provide an overview on the use of SERS in the studies of monolayers of adsorbed molecules, both organic and inorganic in nature, and on how SERS can complement high-resolution techniques such as X-ray Crystography or Nuclear Magnetic Resonance Spectroscopy in probing planar molecular systems. A comparison between SERS and SEIRA (Surface Enhanced Infra-Red Absorption) will also be included. Finally, issues of hot-spot sizes pertaining to the SERS studies of macromolecular studies will also be covered.

Title: A Review of Fluorescence Lifetime Techniques Applied for Biomedical Diagnosis
Author: Fu Chit Yaw, Ng Beng Koon Sirajuddin and Olivo M
Abstract: The paper will entail the working principles of fluorescence lifetime techniques which gain increasing popularity in biomedical diagnosis. Its applications in biosensing and imaging will be highlighted. Besides, the recent advancement in instrumentation and data analysis will also be discussed.

Title: Ultrafast Laser-based Spectroscopy and Sensing
Authors: Megan R. Leahy-Hoppa¹, Joseph A. Miragliotta¹, Robert Osiander¹, Jennifer Burnett², Caroline McEnnis³, James B. Spicer³
Affiliations: ¹ The Johns Hopkins University Applied Physics Laboratory, Milton S. Eisenhower Research Center, Laurel, MD; Megan.Leahy-Hoppa@jhuapl.edu (M.R.L.-H.)
² University of Louisville, Department of Physics and Astronomy, Louisville, KY
³ The Johns Hopkins University, Department of Material Science, Baltimore, MD
Abstract: Ultrafast pulsed lasers find application in a range of spectroscopy and sensing techniques including laser induced breakdown spectroscopy (LIBS), Raman spectroscopy, terahertz (THz) spectroscopy, and coherent anti-Stokes Raman spectroscopy (CARS). Whether based on absorption or emission processes, the characteristics of these techniques are heavily influenced by the use of ultrafast pulses in the signal generation process. Depending on the energy of the pulses used, the essential laser interaction process can primarily involve lattice vibrations, molecular rotations, or a combination of excited states produced by laser heating. While some of these techniques are currently confined to sensing at close ranges, others can be implemented for remote spectroscopic sensing owing principally to the laser pulse duration. We present a review of ultrafast laser-based spectroscopy techniques and discuss the use of these techniques to current and potential chemical and environmental sensing applications.

Type of Paper: Review
Title: The Use of Fiber Lasers for Intra-Cavity Sensing
Authors: A.V. Kir’yanov and Yu.O. Barmenkov
Affiliation: Centro de Investigaciones en Optica Loma del Bosque 115, Col. Lomas del Campestre, Leon 37150, Guanajuato, Mexico; Tel. (52) (477) 4414200, Fax. (52) (477) 4414209, Email: kiryanov@cio.mx
Abstract: The current state of the art of intra-cavity fiber laser sensors (ICFLS) is drawn and the most representative results in the field are reviewed. Among a variety of ICFLS schemes developed to the date in the present review are of close attention the ones based on the sensing of cavity loss variations with a sensor head being a part of a fiber laser. Such ICFLS provide a row of remarkable advantages including high sensitivity and the possibility to transfer the sensed intra-cavity loss change into a temporal or frequency domain that considerably enhances the sensor functionality and hereby permits to apply simple detection schemes. Invaluable in some arrangements is the use of fiber Bragg grating as an intra-cavity sensing element of a fiber laser, or a special implementation of the latter as a distributed feedback structure, the particular cases of ICFLS to be reviewed. Gas detection and gas spectroscopy, the measurements of refractive index, strain, temperature and pressure, and even water flows and waves are discussed below as the most spectacular examples of ICFLS applications.

Type of Paper: Article
Title: Enzyme Activity Measurement with Infrared Spectroscopy
Authors: Saroj Kumar and Andreas Barth
Affiliation: Department of Biochemistry and Biophysics, The Arrhenius Laboratories for Natural Sciences, Svante Arrhenius väg 16, Stockholm University, SE-106 91 Stockholm, Sweden; E-Mail: Andreas.Barth@dbb.su.se
Abstract: Fourier transform infrared (FTIR) spectroscopy provides a direct, "on-line" monitor of enzymatic reactions. Measurement of enzymatic activity is based on the fact that the infrared spectra of reactants and products of an enzymatic reaction are usually different. Several examples are given including ATP hydrolysis by the sarcoplasmic reticulum Ca²⁺-ATPase. The main advantage of the infrared method is that it observes the reaction of interest directly, i.e. no activity assay is required that converts the progress of the reaction into an observable quantity.

Type of Paper: Review
Title: Laser Spectroscopic Study on the Encapsulation Structure of Functional Molecules in Supersonic Jets
Authors: Ryoji Kusaka, Yoshiya Inokuchi and Takayuki Ebata
Affiliation: Department of Chemistry, Vice Dean, Graduate School of Science, Hiroshima University, Kagamiyama 1-3-1, Higashi-hiroshima, 739-8526, Japan; E-Mail: tebata@hiroshima-u.ac.jp (T.E.)
Abstract: In this paper, we report our study on the mechanism of the complex formation of functional molecules by uses of a supersonic jet, laser spectroscopy and quantum chemical calculations. The host molecules chosen are calixarene (CA) and benzo-crown-ether (BC). The cold gaseous complexes are generated in the supersonic jet and the electronic spectra, mass spectra, and IR spectra are obtained by laser-induced fluorescence (LIF), resonance enhanced multiphoton ionization (REMPI), and infrared (IR) - ultraviolet (UV) double resonance spectroscopy. We will discuss the complex structures and the reshaping of the conformations of the host molecules upon the encapsulation of guest species.

Type of Paper: Review
Title: Some Recent Applications of Fluorescence Recovery after Photobleaching (FRAP) to Membrane Protein Studies
Authors: Gamal Rayan, Nicolas Taulier, Frederic Pincet and Wladimir Urbach
Affiliation: Laboratoire de Physique Statistique, Ecole Normale Supérieure, Paris, France; E-Mail: gamal.rayan@lps.ens.fr (G.R.)
Abstract: This review will examine some recent applications of fluorescence recovery after photobleaching (FRAP) to membrane proteins studies. Initially, we will discuss the lateral diffusion of membrane proteins as measured by FRAP. Then, we will talk about the use of FRAP to probe interactions between membrane proteins by obtaining fundamental information such as geometry and stoichiometry of the interacting complex.

Type of Paper: Review
Title: From Fundamental to Advanced Applications of Terahertz Time-Domain Spectroscopy
Author: Withawat Withayachumnankul and Derek Abbot
Affiliation: School of Electrical & Electronic Engineering , The University of Adelaide, Adelaide, SA 5005, Australia; E-Mail: withawat@eleceng.adelaide.edu.au
Abstract: Terahertz time-domain spectroscopy (THz-TDS) offers an efficient and unparalleled approach to broadband T-ray generation and detection in the spectral range between 0.1 and 10 THz. As a result, observation of T-ray responses of materials via THz-TDS has opened up opportunities to researchers in a wide range of disciplines. Furthermore, interactions between T-rays and materials have been further exploited in many practical applications, ranging from security controls to medical diagnoses to molecular sensing. This article reviews a myriad of significant implementations of THz-TDS, from fundamental material studies to advanced applications.

Type of Paper: Article
In Situ SERS Ultra-Trace Detection of Perchlorate in Water using flow-through geometry
Authors: Yun Han ¹, Svetlana Sukhishvili ² and Henry Du ¹
Affiliations: ¹ Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, Castle Point on Hudson, NJ 07030, USA; E-Mails: yhan@stevens.edu (Y.H.), hdu@stevens.edu (H.D.)
² Department of Chemistry, Chemical Biology and Biomedical Engineering, Stevens Institute of Technology, Hoboken, Castle Point on Hudson, NJ 07030, USA; E-Mail: ssukhishvili@stevens.edu
Abstract: We report a facile method for the use of the commercial glass capillary with immobilized Ag nanoparticles on the surface of inside wall as a flow-through sensing geometry for in situ and ultra-trace detection of perchlrate in water of minute volume by surface-enhanced Raman scattering (SERS). Citrate reduced Ag nanoparticles were immobilized in the glass capillary with controlled coverage density via (3-aminopropyl)trimethoxysilane–tetramethoxysilane (APTMS) mediated self-assembly approach, followed by surface modification by cysteamine in aqueous solution to replace adsorbed citrate compound and possess positive surface charges. A detection limit of 10^-8 M for perchlorate (ClO_4^-) in Milli-Q water of ~ 40 μL has been achieved using these Ag nanoparticles modified capillaries by means of SERS. Such SERS active platform can be reused without any memory effect after thorough rinsing with basic water at pH 11. The measurements of ClO_4^- in presence of other anions including sulfate, nitrate and chlorite were also studied and the results shows that at 1 mM concentration, nitrate has no interference with ClO_4^- detection, a detection limit of 10^-6 M ClO_4^- was achieved with the presence of sulfate, chlorite anions have a several interference however could be removed from the solution before SERS measurements. Our results show that these SERS active capillaries can be potentially a robust flow-through sensing platform for rapid, in situ monitoring of ClO_4^- in environmental water.
Keywords: surface-enhanced Raman scattering; Ag nanoparticles; flow-through geometry; in situ detection

Type of Paper: Review
Title: Laser Spectroscopy in Chemical Sensing
Authors: W. Chen ¹, T. Wu ^1,2, J. Cousin ¹, C. Lengignon ¹, E. Fertein ¹, X. Gao ², W. Zhao ², W. Zhang ² and Y. Wang ²
Affiliation: ¹ Laboratoire de Physicochimie de l’Atmosphère, CNRS UMR 8101, Université du Littoral Côte d’Opale, 189A, Av. Maurice Schumann, 59140 Dunkerque, France; E-Mail: chen@univ-littoral.fr
² Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Abstract: The state-of-the-art of laser spectroscopic techniques applied to chemical species sensing will be reviewed. Applications in various fields such as Isotope ratio determination, environmental air monitoring, combustion emission measurements and breath analysis will be presented.

Type of Paper: Article
Title: Spectroscopic Interpretation of PAH-Spectra in Soil Media and Its Application into Soil Monitoring
Authors: Eun-Joung Ko ¹, Kyoung-Woong Kim ², Kihong Park ², Jiwon Kim ², Se-Yeong Hamm ³ and Uwe Wachsmuth ⁴
Affiliations: ¹ Korea Institute of R & DB Human Resources Development, Daejeon 305-340, Korea
² Deparment of Environmental Science and Engineering, Gwangju Institute of Science and Technology, Gwangju 500-712, Korea; E-Mail: kwkim@gist.ac.kr (K.-W.K.)
³ Division of Earth Environmental System, College of Natural Science, Pusan National University, Busan, Korea
⁴ LGG, Goettingen
Abstract: Recent progress in the use of a fiber optic wave guide for remote sensing and inexpensive laser sources to enhance sensitivity has made fluorescence techniques rich for PAHs classification and estimation. For the assessment of the feasibility of LIF spectroscopy for soil monitoring, the variation of fluorescence intensity by the heterogeneity and complexity of soil media should be examined. In order to get insight into the interaction between contaminant and surrounding environment, soil media with various matrix conditions such as polarity, grain size, water/solvent addition have been studied in terms of fluorescence spectral structure as well as the intensity. The different soil type showed the distinguishable fluorescence spectral structure of the contaminant implying dissimilar interaction or binding of contaminants on soil surface. More interestingly, solvent and water addition showed different response in fluorescence spectral structure showing their effect on interaction between contaminant and soil media. These results supports that the spectral structure contains information on the contaminant–soil interactions; therefore the contaminant can be used as a fluorescence probe for these interactions.

Type of Paper: Review
Title: Laser Induced Plasma Spectroscopy for Elemental Analysis in Environmental, Cultural Heritage and Space Applications: A Review of Methods and Results
Authors: Rosalba Gaudiuso ¹, M. Dell’Aglio ², O.De Pascale ², G.S. Senesi ² and A. De Giacomo ^1,2
Affiliations: ¹ Department of Chemistry, University of Bari, via Orabona 4, 79126, Bari, Italy; E-Mail: rosalba.gaudiuso@ba.imip.cnr.it
² IMIP-CNR sec. Bari, via Amendola 122/D, 70126, Bari, Italy
Abstract: Analytical applications of Laser Induced Breakdown Spectroscopy (LIBS), namely optical emission spectroscopy of laser-induced plasmas, have been constantly growing thanks to its intrinsic conceptual simplicity and versatility. Qualitative and quantitative analysis can be performed by LIBS both by drawing calibration lines and by using calibration-free methods and some of its features, such as fast multi-elemental response, micro-destructiveness, portability, have rendered it particularly suitable in the field of geochemical and cultural heritage applications. This work will review LIBS progresses in these areas, reporting and discussing results obtained for both terrestrial and space samples, such as soils, rocks and meteorites, and for cultural heritage samples, ranging from buildings to objects of different kinds.

Type of Paper: Review
Title: Generation of Multicolored Femtosecond Laser Pulses by Using Cascaded Four-Wave Mixing Process in Transparent Bulk Media
Authors: Jun Liu ^1,2 and Takayoshi Kobayashi ^1,2,3,4
Affiliations: ¹ Department of Applied Physics and Chemistry and Institute for Laser Science, University of Electro-Communications, Chofugaoka 1-5-1, Chofu, Tokyo 182-8585 Japan; E-Mail: jliu@ils.uec.ac.jp (J.L.)
² International Cooperative Research Project (ICORP), Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
³ Department of Electrophysics, National Chiao Tung University, 1001 Ta Hsueh Rd. Hsinchu 300, Taiwan
⁴ Institute of Laser Engineering, Osaka University, Yamadakami 2-6, Suita 565-0871, Ibaraki 567-0047, Japan
Abstract: Cascaded four-wave mixing was theoretically and experimentally studied in transparent bulk media. As many as fifteen spectral up-shifted pulses and two spectral downshifted pulses were obtained with spectral bandwidth broader than 1.8 octaves. The wavelengths of the sidebands are continuously tunable from near ultraviolet to near infrared. The obtained sidebands have good beam quality with M2 factor better than 1.1 and Gaussian spatial profile. The pulse energy of the first-order sideband can reach 1 ?J with power stability smaller than 1 % RMS. As short as 15-fs compressed pulses, which were nearly transform-limited, were obtained when one of the two input beams was appropriately negatively chirped and the other was positively chirped. Moreover, broadband 2-D multicolored arrays with more than ten periodic columns and more than ten rows were generated when a sapphire plate was used as the bulk medium. The characterization showed that the sidebands have good enough qualities for various experiments in ultrafast time-resolved spectroscopy, for example multicolor pump-probe experiment.

Type of Paper: Article
Title: Transversely Excited Multipass Photoacoustic Cell Using
Electromechanical Film as Microphone
Authors: Jaakko Saarela, Johan Sand, Tapio Sorvajärvi and Juha Toivonen
Affiliation: Optics Laboratory, Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland; E-Mail: jaakko.saarela@tut.fi
Abstract: A novel multipass photoacoustic cell with five stacked electromechanical films as a microphone has been constructed, tested and characterized. The photoacoustic cell is an open rectangular structure with two steel plates facing each other. The longitudinal acoustic resonances are excited transversely in an optical multipass configuration. A detection limit of 22 ppb for NO₂ in N₂ was achieved by using the maximum of 70 laser beams between the resonator plates. The corresponding minimum detectable absorption and the normalized noiseequivalent absorption coefficients were 2.23 x 10^-7 cm^-1 and 3.2 x 10^-9 cm^-1WHz^-1/2, respectively.
Keywords: Multipass; Photoacoustic; Spectroscopy; Longitudinal resonance; Transversal excitation; Transducer; Electromechanical film microphone; EMFIT film

Type of Paper: Review
Title: Principals of Raman Spectroscopy and Optical Trapping Using Fibre Lasers
Authors: Sebastian Dochow ¹, Christoph Krafft ¹, Thomas Henkel ¹, Jens Albers ¹ and Jürgen Popp ^1,2
Affiliations: ¹ Institute of Photonic Technology, Jena, Germany; E-Mail: christoph.krafft@ipht-jena.de (C.K.)
² Institute of Physical Chemistry, University Jena, Jena, Germany
Abstract: Raman spectroscopy is a very powerful tool for label-free differentiation of cells and tissue. Detection methods are under development to utilize these prospects to identify cells in body fluids such as saliva, urine or blood. Raman spectrometers are combined with microfluidic devices and optical traps for manipulation, data acquisition and sorting of cells. The optical traps are constructed using two single mode fiber lasers. This contribution first describes the principles of optical Lab-on-a-Chip setups. Then, microfluidic chip and capillary-based systems are compared. For single cell control different functionality structures, such as single cell streaming, hydrodynamic cell focussing, flow speed modification and cell sorting have been implemented in a microfluidic chip. Finally, Raman spectra of trapped cells are presented.

Type of Paper: Review
Title: Effect of Atmospheric Conditions on LIBS Spectra
Authors: Andrew J. Effenberger and Jill R. Scott
Affiliation: Idaho National Laboratory, Science and Technology, Chemical Sciences, 1765 North Yellowstone Hwy, P.O. Box 1625, Idaho Falls, ID 83415-2208, USA; E-Mail: Jill.Scott@inl.gov (J.R.S.)
Abstract: Laser-induced breakdown spectroscopy (LIBS) is typically performed at ambient Earth atmospheric conditions. However, interest in LIBS in other atmospheric conditions has increased in recent years, especially for use in space exploration (e.g., Mars and Lunar) or to improve resolution for isotopic signatures. This review focuses on what has been reported about the performance of LIBS in reduced pressure environments as well as in various gases other than air.

Type of Paper: Article
Title: Spectroscopic Remote Detection, Identification, Discrimination and Quantification of High Explosives
Authors: Leonardo C. Pacheco-Londoño, William Ortiz, Oliva M. Primera-Pedrozo, Hilsamar Félix-Rivera and Samuel P. Hernandez-Rivera
Affiliation: Center for Sensor Development, Chemical Imaging Center, ALERT DHS-COE, Department of Chemistry, University of Puerto Rico-Mayaguez, Call BOX 9000, Mayaguez, PR 00681; E-Mails: samuel.hernandez3@upr.edu (S.P.H.-R.); pachecolc@yahoo.com (L.C.P.-L.)
Abstract: This contribution describes the design, assembly and testing of two Remote Raman System (RRS) used for remote detection of chemical threat compounds: a continuous wave (CW) laser based RRS and a pulsed laser spectroscopic remote detection system. Comparison of figures of merit of both systems was based on limits of detection achieved and overall performance of the detection systems. The remote detection systems were used to obtain Raman spectra of Chemical Warfare Agents Simulants (CWAS) and Toxic Industrial Compounds (TIC) at laboratory scale at 6.6 m source-target distance. The CW prototype system consisted of a Raman Spectrometer equipped with a CCD detector, reflecting telescope, fiber optic assembly and single line wavelength laser source (532.0, 514.5, 488.0, 351.1 and 363.8 nm). The pulsed system was based on a 532.0 nm, 5 ns pulses operating at 10 Hz and coupled to an Andor Technologies Shamrock spectrograph equipped with an intensified-CCD detector. The collector telescopes were coupled to the Raman spectrographs using an optical fiber and filters for rejection of laser radiation and Rayleigh scattering. Two quartz convex lenses collimate the light from the telescopes output and direct it to the fiber optic assembly from which the telescope focusing eyepiece was removed. To test the standoff sensing system, the Raman Telescope was used in detection of liquid TICs: benzene, chlorobenzene, toluene, carbon tetrachloride and carbon disulfide. Other compounds studied were CWAS: dimethylethyl phosphonate, 2-chloroethyl ethyl sulfide and 2-(butylamino) ethanethiol. Raman scattering cross sections of liquid CWAS were measured using single line sources at 532.0, 488.0, 363.8 and 351.1 nm. Samples were placed in glass and quartz vials at the standoff distance from the telescope for the Remote Raman measurements. A quantification study of DMMP dissolved in water was also completed as part of the system performance tests. Spectra of compounds were acquired in the Raman Shift range of 100-1800 cm^-1 using laser powers varying from 0.050 to 1 W and integration times of 1 to 30 s.

Type of Paper: Article
Title: Comparative Laser Spectroscopy Diagnostics for Ancient Metallic Artefacts Exposed to Environmental Pollution
Authors: Łukasz Ciupiński ¹, Elżbieta Fortuna ¹, Halina Garbacz ¹, Andrzej Koss ², Krzysztof Jan Kurzydłowski ², Jan Marczak ³, Janusz Mróz ², Tomasz Onyszczuk ¹, Antoni Rycyk ³, Antoni Sarzyński ³, Wojciech Skrzeczanowski ³, Marek Strzelec ³, Anna Zatorska ² and Zofia Żukowska ⁴
Affiliations: ¹ Faculty of Materials Science and Engineering, Warsaw University of Technology, Warsaw, Poland
² Inter-Academy Institute for Conservation and Restoration of Works of Art, Academy of Fine Arts in Warsaw, Poland
³ Institute of Optoelectronics, Military University of Technology, Warsaw, Poland; E-Mail: mstrzelec@wat.edu.pl (M.S.)
⁴ Faculty of Chemistry, Warsaw University of Technology, Warsaw, Poland
Abstract: Metal art works experience the influence of corrosion and oxidation processes due to the many reactive agents present in the air, water and in the ground where these objects were kept over hundreds of years. These are the cases of archaeological metals when they are recovered from the excavation sites as well as artefacts host in polluted environments. Stabilization of the conservation state of these objects needs precise diagnostics of accrued surface layers and identification of original, historical materials before further protective treatments, including safe laser cleaning of unwanted layers. Paper presents analyses of chemical composition and stratigraphy of corrosion products with the use of laser induced breakdown spectroscopy (LIBS) and Raman spectroscopy. The discussion of the results is supported by materials studies (SEM-EDS, XRF, ion-analyses). The tests were performed on several samples taken from original objects, including copper roofing at Wilanów Palace in Warsaw and Charles Poznański Palace in Łódź, bronze decorative figures from Wilanów Palace gardens, and five archaeological examples of old jewellery (different copper alloys). Work has been performed as a part of MATLAS project in the frames of EEA and Norway Grants (www.matlas.eu) and the results enable to compare the methodology and to elaborate cooperative diagnostic procedures of independent laboratories of three project partners.

Type of Paper: Review
Title: Quantum Cascade Laser Absorption Spectroscopy as a Plasma Diagnostic Tool: An Overview
Authors: S. Welzel ^1,3, F. Hempel ¹, N. Lang ¹, P.B. Davies ², J. Röpcke ¹
Affiliations: ¹ INP Greifswald, Felix-Hausdorff-Str. 2, 17489 Greifswald, Germany; E-Mail: welzel@physik.uni-greifswald.de (S.W.)
² University of Cambridge, Lensfield Road, Cambridge CB2 1EW, Great Britain
³ Present Address: Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, The Netherlands
Abstract: The recent availability of pulsed and continuous wave intersubband and interband cascade lasers as alternative thermoelectrically cooled tuneable light sources in the mid-infrared spectral range has led to improvements and new developments in chemical sensing techniques using in-situ laser absorption spectroscopy for plasma diagnostic purposes. The aim of this article is therefore two-fold: (i) to summarise challenges which are connected to the application of quantum cascade lasers in such environments, particularly under low pressure conditions, and, (ii) to provide an overview about recent spectroscopic results obtained in different kinds of plasma both in research and industry.