Broadband mid-infrared molecular spectroscopy is essential for detection and identification of many chemicals and materials. In this report, we present stand-off mid-infrared spectra of 1,3,5-trinitro-1,3,5-triazine or cyclotrimethylene trinitramine (RDX) residues on a stainless-steel surface measured by a broadband external cavity quantum cascade laser (QCL) system. The pulsed QCL is continuously scanned over 800 cm−1 in the molecular fingerprint region and the amplitude of the reflection signal is measured by either a boxcar-averager-based scheme or a lock-in-amplifier-based scheme with 1 MHz and 100 kHz quartz crystal oscillators. The main background noise is due to the laser source instability and is around 0.1% of normalized intensity. The direct absorption spectra have linewidth resolution around 0.1 cm−1 and peak height sensitivity around 10−2 due to baseline interference fringes. Stand-off detection of 5–50 µg/cm2 of RDX trace adsorbed on a stainless steel surface at the distance of 5 m is presented.
TittelF.K.LewickiR.LascolaR.McWhorterS.“Emerging Infrared Laser Absorption Spectroscopic Techniques for Gas Analysis”. In: GeigerW.M.RaynorR.W. (eds). Trace Analysis of Specialty and Electronic Gases, Chichester, UK: Wiley, 2013, pp. 71–109.
4.
KosterevA.TittelF.“Chemical Sensors Based on Quantum Cascade Lasers”. IEEE J. Quantum Electronics2002; 38(6): 582–591.
5.
CurlR.F.CapassoF.GmachlC.KosterevA.A.McManusB.. “Quantum Cascade Lasers in Chemical Physics”. Chem. Phys. Lett2010; 487(13): 406.
6.
NamjouK.CaiS.WhittakerE.A.FaistJ.GmachlC.. “Sensitive Absorption Spectroscopy with a Room-Temperature Distributed-Feedback Quantum-Cascade Laser”. Opt. Lett1998; 23(3): 219–221.
7.
GagliardiG.TamassiaF.NataleP.D.GmachlC.CapassoF.. “Sensitive Detection of Methane and Nitrous Oxide Isotopomers Using a Continuous Wave Quantum Cascade Laser”. Eur. Phys. J. D2002; 19(3): 327–331.
KosterevA.A.MalinovskyA.L.TittelF.K.GmachlC.CapassoF.. “Cavity Ringdown Spectroscopic Detection of Nitric Oxide with a Continuous-Wave Quantum-Cascade Laser”. Appl. Opt2001; 40(30): 5522–5529.
10.
LiuX.XuY.SuZ.TamW.S.LeonovI.“Jet-Cooled Infrared Spectra of Molecules and Complexes with a CW Mode-Hop-Free External-Cavity QCL and a Distributed-Feedback QCL”. Appl. Phys. B: Lasers Opt2010; 102(3): 629–639.
KosterevA.A.TittelF.K.SerebryakovD.V.MalinovskyA.L.MorozovI.V.“Applications of Quartz Tuning Forks in Spectroscopic Gas Sensing”. Rev. Sci. Instrum2005; 76(4): 043105.
LiuK.YiH.KosterevA.A.ChenW.DongL.. “Trace Gas Detection Based on Off-Beam Quartz Enhanced Photoacoustic Spectroscopy: Optimization and Performance Evaluation”. Rev. Sci. Instrum2010; 81(10): 103103.
15.
DongL.SpagnoloV.LewickiR.TittelF.K.“Ppb-Level Detection of Nitric Oxide Using an External Cavity Quantum Cascade Laser Based QEPAS Sensor”. Opt. Express2011; 19(24): 24037–24045.
16.
DongL.LewickiR.LiuK.BuerkiP.R.WeidaM.J.. “Ultra-Sensitive Carbon Monoxide Detection by Using EC-QCL Based Quartz-Enhanced Photoacoustic Spectroscopy”. Appl. Phys. B2012; 107(2): 275–283.
17.
KachanovA.KoulikovS.TittelF.K.“Cavity-Enhanced Optical Feedback-Assisted Photo-Acoustic Spectroscopy with a 10.4 m External Cavity Quantum Cascade Laser”. Appl. Phys. B2013; 110(1): 47–56.
18.
BartaliniS.BorriS.De NataleP.“Doppler-Free Polarization Spectroscopy with a Quantum Cascade Laser at 4.3 µm”. Opt. Express2009; 17(9): 7440–7449.
19.
LewickiR.DotyJ.H.CurlR.F.TittelF.K.WysockiG.“Ultrasensitive Detection of Nitric Oxide at 5.33 m by Using External Cavity Quantum Cascade Laser-Based Faraday Rotation Spectroscopy”. Proc. Nat. Acad. Sci2009; 106(31): 12587–12592.
20.
Van NesteC.W.SenesacL.R.YiD.ThundatT.“Standoff Detection of Explosive Residues Using Photothermal Microcantilevers”. Appl. Phys. Lett2008; 92(13): 134102.
21.
WysockiG.LewickiR.CurlR.TittelF.DiehlL.. “Widely Tunable Mode-Hop Free External Cavity Quantum Cascade Lasers for High Resolution Spectroscopy and Chemical Sensing”. Appl. Phys. B2008; 92(3): 305–311.
KuligowskiJ.QuintsG.LendlB.“High Performance Liquid Chromatography with On-Line Dual Quantum Cascade Laser Detection for the Determination of Carbohydrates, Alcohols and Organic Acids in Wine and Grape Juice”. Appl. Phys. B2010; 99(4): 833–840.
24.
Y. Xu, X. Liu, Z. Su, R.M. Kulkarni, W.S. Tam, et al. “Application of Quantum Cascade Lasers for Infrared Spectroscopy of Jet-Cooled Molecules and Complexes”. Proc. SPIE 7222, Quantum Sensing and Nanophotonic Devices VI, 722208 (26 January 2009); doi: 10.1117/12.814878.
25.
LiuX.XuY.“Infrared and Microwave Spectra of the Acetylene-Ammonia and Carbonyl Sulfide-Ammonia Complexes: A Comparative Study of a Weak CHN Hydrogen Bond and an SN Bond”. Phys. Chem. Chem. Phys2011; 13(31): 14235–14242.
26.
HuggerS.FuchsF.JarvisJ.KinzerM.YangQ.K.. “Broadband-Tunable External-Cavity Quantum Cascade Lasers for the Spectroscopic Detection of Hazardous Substances”. Proc. SPIE 8631, Quantum Sensing and Nanophotonic Devices X. 86312I (February 4, 2013); doi:10.1117/12.2008880.
27.
NelsonD.D.McManusB.UrbanskiS.HerndonS.ZahniserM.S.“High Precision Measurements of Atmospheric Nitrous Oxide and Methane Using Thermoelectrically Cooled Mid-Infrared Quantum Cascade Lasers and Detectors”. Spectrochim. Acta, Part A2004; 60(14): 3325–3335.
28.
McManusJ.B.NelsonD.D.HerndonS.C.ShorterJ.H.ZahniserM.S.. “Comparison of CW and Pulsed Operation with a TE-Cooled Quantum Cascade Infrared Laser for Detection of Nitric Oxide at 1900 cm–1”. Appl. Phys. B2006; 85(2–3): 235–241.
29.
GrouiezB.ParvitteB.JolyL.CourtoisD.ZeninariV.“Comparison of a Quantum Cascade Laser Used in Both CW and Pulsed Modes. Application to the Study of SO2 Lines Around 9 µm”. Appl. Phys. B2007; 90(2): 177–186.
BaiY.SlivkenS.KuboyaS.DarvishS.R.RazeghiM.“Quantum Cascade Lasers that Emit More Light than Heat”. Nat. Photonics2010; 4(2): 99–102.
33.
C.W. Van Neste, X. Liu, M. Gupta, S. Kim, Y. Tsui, et al. “Standoff Detection of Explosive Residues on Unknown Surfaces”. Proc. SPIE. 2012. 83732F.
34.
LiuX.Van NesteC.W.GuptaM.TsuiY.Y.KimS.. “Standoff Reflection-Absorption Spectra of Surface Adsorbed Explosives Measured with Pulsed Quantum Cascade Lasers”. Sens. Actuators, B2014; 191: 450–456.
35.
MammezD.StoefflerC.CousinJ.VallonR.MammezM.. “Photoacoustic Gas Sensing with a Commercial External Cavity-Quantum Cascade Laser at 10.5 µm”. Infrared Phys. Technol2013; 61: 14–19.
36.
RothmanL.GordonI.BabikovY.BarbeA.Chris BennerD.. “The HITRAN2012 Molecular Spectroscopic Database”. J. Quant. Spectrosc. Radiat. Transfer2013; 130: 4–50.
37.
AsherW.E.Willard-SchmoeE.“Vibrational Sum-Frequency Spectroscopy for Trace Chemical Detection on Surfaces at Stand-Off Distances”. Appl. Spectrosc2013; 67(3): 253–260.
38.
MoltR.W.WatsonT.LotrichV.F.BartlettR.J.“RDX Geometries, Excited States, and Revised Energy Ordering of Conformers via MP2 and CCSD(T) Methodologies: Insights into Decomposition Mechanism”. J. Phys. Chem. A2011; 115(5): 884–890.
39.
BartaliniS.VitielloM.S.NataleP.D.“Quantum Cascade Lasers: A Versatile Source for Precise Measurements in the Mid/Far-Infrared Range”. Meas. Sci. Technol2014; 25(1): 012001.
