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Cheng Q, Guan Y, Xu G, Dong J, Liu N. High-performance CO detection based on a PhC cavity in terahertz band. Heliyon 2024; 10:e32795. [PMID: 38975096 PMCID: PMC11225829 DOI: 10.1016/j.heliyon.2024.e32795] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 05/20/2024] [Accepted: 06/10/2024] [Indexed: 07/09/2024] Open
Abstract
Combined with the light absorption from molecular vibration, photonic crystal (PhC) cavity structures have gradually shown great potential in gas detection, particularly for toxic gases. We proposed a PhC cavity with a high-quality factor of 1.24 × 106 and a small mode volume of 2.3 × 10-4 (λ/n)3, which was used for carbon monoxide detection. To reduce the interference of other gases, we set the resonance frequency in the terahertz band. The numerical analysis shows that the structure has good selectivity and high sensitivity, and the linear fitting of the results provides the possibility to realize the application, which has great competitiveness in the same type of sensor structure. Additionally, we also proved that the interference of H2O and CO2 on the CO sensing can be ignored, and it supports the detection of CO without pre-drying.
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Affiliation(s)
- Qi Cheng
- Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao 266520, Shandong, China
| | - Yuanlin Guan
- Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao 266520, Shandong, China
| | - Guangsheng Xu
- Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao 266520, Shandong, China
| | - Jianlin Dong
- Mechanical and Automotive Engineering, Qingdao University of Technology, Qingdao 266520, Shandong, China
| | - Na Liu
- Measurement Technology and Instrumentation Key Lab of Hebei Province, Yanshan University, Qinhuangdao 066004, China
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2
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Cao Y, Nallappan K, Xu G, Skorobogatiy M. Resonant Gas Sensing in the Terahertz Spectral Range Using Two-Wire Phase-Shifted Waveguide Bragg Gratings. SENSORS (BASEL, SWITZERLAND) 2023; 23:8527. [PMID: 37896620 PMCID: PMC10610679 DOI: 10.3390/s23208527] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2023] [Revised: 10/12/2023] [Accepted: 10/16/2023] [Indexed: 10/29/2023]
Abstract
The development of low-cost sensing devices with high compactness, flexibility, and robustness is of significance for practical applications of optical gas sensing. In this work, we propose a waveguide-based resonant gas sensor operating in the terahertz frequency band. It features micro-encapsulated two-wire plasmonic waveguides and a phase-shifted waveguide Bragg grating (WBG). The modular semi-sealed structure ensures the controllable and efficient interaction between terahertz radiation and gaseous analytes of small quantities. WBG built by superimposing periodical features on one wire shows high reflection and a low transmission coefficient within the grating stopband. Phase-shifted grating is developed by inserting a Fabry-Perot cavity in the form of a straight waveguide section inside the uniform gratings. Its spectral response is optimized for sensing by tailoring the cavity length and the number of grating periods. Gas sensor operating around 140 GHz, featuring a sensitivity of 144 GHz/RIU to the variation in the gas refractive index, with resolution of 7 × 10-5 RIU, is developed. In proof-of-concept experiments, gas sensing was demonstrated by monitoring the real-time spectral response of the phase-shifted grating to glycerol vapor flowing through its sealed cavity. We believe that the phase-shifted grating-based terahertz resonant gas sensor can open new opportunities in the monitoring of gaseous analytes.
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Affiliation(s)
- Yang Cao
- Center for Advanced Laser Technology, Hebei University of Technology, 5340 Xiping Road, Tianjin 300401, China
- Engineering Physics, Polytechnique Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, QC H3C 3A7, Canada; (K.N.); (G.X.)
| | - Kathirvel Nallappan
- Engineering Physics, Polytechnique Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, QC H3C 3A7, Canada; (K.N.); (G.X.)
| | - Guofu Xu
- Engineering Physics, Polytechnique Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, QC H3C 3A7, Canada; (K.N.); (G.X.)
| | - Maksim Skorobogatiy
- Engineering Physics, Polytechnique Montréal, C.P. 6079, Succ. Centre-Ville, Montréal, QC H3C 3A7, Canada; (K.N.); (G.X.)
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3
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Elmaleh C, Simon F, Decker J, Dumont J, Cazier F, Fourmentin M, Bocquet R, Cuisset A, Mouret G, Hindle F. THz cavity ring-down quantitative gas phase spectroscopy. Talanta 2022. [DOI: 10.1016/j.talanta.2022.124097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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4
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Lu JY, You B, Wang JY, Jhuo SS, Hung TY, Yu CP. Volatile Gas Sensing through Terahertz Pipe Waveguide. SENSORS 2020; 20:s20216268. [PMID: 33153176 PMCID: PMC7662959 DOI: 10.3390/s20216268] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/27/2020] [Revised: 10/31/2020] [Accepted: 11/02/2020] [Indexed: 12/29/2022]
Abstract
Gas sensing to recognize volatile liquids is successfully conducted through pipe-guided terahertz (THz) radiation in a reflective and label-free manner. The hollow core of a pipe waveguide can efficiently deliver the sensing probe of the THz confined waveguide fields to any place where dangerous vapors exist. Target vapors that naturally diffuse from a sample site into the pipe core can be detected based on strong interaction between the probe and analyte. The power variation of the THz reflectance spectrum in response to various types and densities of vapors are characterized experimentally using a glass pipe. The most sensitive THz frequency of the pipe waveguide can recognize vapors with a resolution at a low part-per-million level. The investigation found that the sensitivity of the pipe-waveguide sensing scheme is dependent on the vapor absorption strength, which is strongly related to the molecular amount and properties including the dipole moment and mass of a gas molecule.
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Affiliation(s)
- Ja-Yu Lu
- Department of Photonics, National Cheng Kung University, No. 1 University Road, Tainan 70101, Taiwan; (J.-Y.W.); (S.-S.J.)
- Correspondence: (J.-Y.L.); (B.Y.)
| | - Borwen You
- Department of Applied Physics, Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan
- Correspondence: (J.-Y.L.); (B.Y.)
| | - Jiun-You Wang
- Department of Photonics, National Cheng Kung University, No. 1 University Road, Tainan 70101, Taiwan; (J.-Y.W.); (S.-S.J.)
| | - Sheng-Syong Jhuo
- Department of Photonics, National Cheng Kung University, No. 1 University Road, Tainan 70101, Taiwan; (J.-Y.W.); (S.-S.J.)
| | - Tun-Yao Hung
- Department of Photonics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan; (T.-Y.H.); (C.-P.Y.)
| | - Chin-Ping Yu
- Department of Photonics, National Sun Yat-sen University, Kaohsiung 80424, Taiwan; (T.-Y.H.); (C.-P.Y.)
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5
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Rothbart N, Holz O, Koczulla R, Schmalz K, Hübers HW. Analysis of Human Breath by Millimeter-Wave/Terahertz Spectroscopy. SENSORS (BASEL, SWITZERLAND) 2019; 19:E2719. [PMID: 31212999 PMCID: PMC6630364 DOI: 10.3390/s19122719] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/08/2019] [Revised: 06/12/2019] [Accepted: 06/13/2019] [Indexed: 11/17/2022]
Abstract
Breath gas analysis is a promising tool for medical research and diagnosis. A particularly powerful technological approach is millimeter-wave/terahertz (mmW/THz) spectroscopy, because it is a very sensitive and highly selective technique. In addition, it offers the potential for compact and affordable sensing systems for wide use. In this work, we demonstrate the capability of a mmW/THz spectrometer for breath analysis. Samples from three volunteers and a sample from ambient air were analyzed with respect to 31 different molecular species. High-resolution absorption spectra were measured by scanning two absorption lines from each species. Out of the 31, a total of 21 species were detected. The results demonstrate the potential of mmW/THz spectroscopy for breath analysis.
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Affiliation(s)
- Nick Rothbart
- Institute of Optical Sensor Systems, German Aerospace Center (DLR), 12489 Berlin, Germany.
- Department of Physics, Humboldt-Universität zu Berlin, 12489 Berlin, Germany.
| | - Olaf Holz
- Fraunhofer Institute for Toxicology and Experimental Medicine ITEM, Biomedical Research in Endstage and Obstructive Lung Disease Hannover (BREATH), 30625 Hannover, Germany.
- The German Center for Lung Research (DZL), 35392 Giessen, Germany.
| | - Rembert Koczulla
- The German Center for Lung Research (DZL), 35392 Giessen, Germany.
- Department of Pulmonology, Institute for Internal Medicine, Philipps-University of Marburg, 35043 Marburg, Germany.
- Schön Klinik Berchtesgadener Land, Department for Pulmonology, Teaching Hospital of the Philipps-University, 35043 Marburg, Germany.
- Teaching Department of the Paracelsus University Salzburg, 5020 Salzburg, Austria.
| | - Klaus Schmalz
- IHP-Leibniz-Institut für innovative Mikroelektronik, 15236 Frankfurt (Oder), Germany.
| | - Heinz-Wilhelm Hübers
- Institute of Optical Sensor Systems, German Aerospace Center (DLR), 12489 Berlin, Germany.
- Department of Physics, Humboldt-Universität zu Berlin, 12489 Berlin, Germany.
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6
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Liu H, Fan YX, Li L, Chen HG, Wang PF, Tao ZY. Self-adaptive terahertz spectroscopy from atmospheric vapor based on Hilbert-Huang transform. OPTICS EXPRESS 2018; 26:27279-27293. [PMID: 30469799 DOI: 10.1364/oe.26.027279] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2018] [Accepted: 09/19/2018] [Indexed: 06/09/2023]
Abstract
Absorption lines of atmospheric vapor commonly appear in terahertz (THz) spectra measured in a humid air environment. However, these effects are generally undesirable because they may mask critical spectroscopic information. Here, a self-adaptive method is demonstrated for effectively identifying and eliminating atmospheric vapor noise from THz spectra of an all-fiber THz system with the Hilbert-Huang transform. The THz signal was decomposed into eight components in different time scales called the intrinsic mode functions and the interference of atmospheric vapor was accurately isolated. A series of experiments confirmed the effectiveness and strong self-adaptiveness of the proposed system in vapor noise elimination.
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7
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Hindle F, Kuuliala L, Mouelhi M, Cuisset A, Bray C, Vanwolleghem M, Devlieghere F, Mouret G, Bocquet R. Monitoring of food spoilage by high resolution THz analysis. Analyst 2018; 143:5536-5544. [DOI: 10.1039/c8an01180j] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
High resolution rotational Terahertz (THz) spectroscopy is suited to studies of numerous polar gas phase molecules, and particularly volatile organic compounds (VOCs). Analysis of the headspace gas of packed Salmon fillets indicates the degree of food spoilage.
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Affiliation(s)
- Francis Hindle
- Laboratoire de Physico-Chimie de l'Atmosphère (LPCA EA 4493)
- Université du Littoral Côte d'Opale
- 59140 Dunkerque
- France
| | - Lotta Kuuliala
- Research Unit Food Microbiology and Food Preservation (FMFP)
- Department of Food Technology
- Safety and Health
- Part of Food2Know
- Faculty of Bioscience Engineering
| | - Meriem Mouelhi
- Laboratoire de Physico-Chimie de l'Atmosphère (LPCA EA 4493)
- Université du Littoral Côte d'Opale
- 59140 Dunkerque
- France
- Laboratoire Dynamique Moléculaire et Matériaux Photoniques
| | - Arnaud Cuisset
- Laboratoire de Physico-Chimie de l'Atmosphère (LPCA EA 4493)
- Université du Littoral Côte d'Opale
- 59140 Dunkerque
- France
| | - Cédric Bray
- Laboratoire de Physico-Chimie de l'Atmosphère (LPCA EA 4493)
- Université du Littoral Côte d'Opale
- 59140 Dunkerque
- France
| | - Mathias Vanwolleghem
- Institute of Electronics
- Microelectronics and Nanotechnology
- CNRS
- Centrale Lille
- ISEN
| | - Frank Devlieghere
- Research Unit Food Microbiology and Food Preservation (FMFP)
- Department of Food Technology
- Safety and Health
- Part of Food2Know
- Faculty of Bioscience Engineering
| | - Gaël Mouret
- Laboratoire de Physico-Chimie de l'Atmosphère (LPCA EA 4493)
- Université du Littoral Côte d'Opale
- 59140 Dunkerque
- France
| | - Robin Bocquet
- Laboratoire de Physico-Chimie de l'Atmosphère (LPCA EA 4493)
- Université du Littoral Côte d'Opale
- 59140 Dunkerque
- France
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8
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Giorio C, Marton D, Formenton G, Tapparo A. Formation of Metal-Cyanide Complexes in Deliquescent Airborne Particles: A New Possible Sink for HCN in Urban Environments. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:14107-14113. [PMID: 29148736 DOI: 10.1021/acs.est.7b03123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Hydrogen cyanide is a ubiquitous gas in the atmosphere and a biomass burning tracer. Reactive gases can be adsorbed onto aerosol particles where they can promote heterogeneous chemistry. In the present study, we report for the first time on the measurement and speciation of cyanides in atmospheric aerosol. Filter samples were collected at an urban background site in the city center of Padua (Italy), extracted and analyzed with headspace gas chromatography and nitrogen-phosphorus detection. The results showed that strongly bound cyanides were present in all aerosol samples at a concentration ranging between 0.3 and 6.5 ng/m3 in the PM2.5 fraction. The concentration of cyanides strongly correlates with concentration of total carbon and metals associated with combustion sources. The results obtained bring evidence that hydrogen cyanide can be adsorbed onto aerosol liquid water and can react with metal ions to form stable metal-cyanide complexes.
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Affiliation(s)
- Chiara Giorio
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova , Via Marzolo 1, 35131 Padova, Italy
- Aix Marseille Univ, CNRS, LCE , Marseille, 13331, France
| | - Daniele Marton
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova , Via Marzolo 1, 35131 Padova, Italy
| | - Gianni Formenton
- ARPAV Environmental Regional Agency , Laboratory Department, via Lissa 6, 30171 Mestre, Venice, Italy
| | - Andrea Tapparo
- Dipartimento di Scienze Chimiche, Università degli Studi di Padova , Via Marzolo 1, 35131 Padova, Italy
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9
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Li Z, Xu D, Yao J. Terahertz generation based on difference frequency generation by rotating fan-out poled LiNbO 3. APPLIED OPTICS 2016; 55:10073-10077. [PMID: 27958419 DOI: 10.1364/ao.55.010073] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Theoretical analysis of terahertz (THz) generation based on difference frequency generation (DFG) by rotating fan-out poled LiNbO3 is presented. The uncertainty of poling vectors during clockwise and counterclockwise rotation of the fan-out poled LiNbO3 at the center of the crystal input face is investigated. The poling period along the propagation direction of the input pump and signal waves during clockwise and counterclockwise rotation is calculated. The dependence of THz vectors on rotation angles is numerically simulated. The relative intensities of a THz wave during clockwise rotation of the fan-out poled LiNbO3 are calculated.
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10
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Rodrigo SG, Martín-Moreno L. Absorption-induced transparency metamaterials in the terahertz regime. OPTICS LETTERS 2016; 41:293-296. [PMID: 26766697 DOI: 10.1364/ol.41.000293] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Contrary to what might be expected, when an organic dye is sputtered onto an opaque holey metal film, transmission bands can be observed at the absorption energies of the molecules. This phenomenon, known as absorption-induced transparency, is aided by a strong modification of the propagation properties of light inside the holes when filled by the molecules. Despite having been initially observed in metallic structures in the optical regime, new routes for investigation and applications at different spectral regimes can be devised. Here, to illustrate the potential use of absorption-induced transparency at terahertz, a method for molecular detection is presented and supported by a theoretical analysis.
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Li H, Laffaille P, Gacemi D, Apfel M, Sirtori C, Leonardon J, Santarelli G, Rösch M, Scalari G, Beck M, Faist J, Hänsel W, Holzwarth R, Barbieri S. Dynamics of ultra-broadband terahertz quantum cascade lasers for comb operation. OPTICS EXPRESS 2015; 23:33270-33294. [PMID: 26831993 DOI: 10.1364/oe.23.033270] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
We present an experimental investigation of the multimode dynamics and the coherence of terahertz quantum cascade lasers emitting over a spectral bandwidth of ~1THz. The devices are studied in free-running and under direct RF modulation. Depending on the pump current we observe different regimes of operation, where RF spectra displaying single and multiple narrow beat-note signals alternate with spectra showing a single beat-note characterized by an intense phase-noise, extending over a bandwidth up to a few GHz. We investigate the relation between this phase-noise and the dynamics of the THz modes through the electro-optic sampling of the laser emission. We find that when the phase-noise is large, the laser operates in an unstable regime where the lasing modes are incoherent. Under RF modulation of the laser current such instability can be suppressed and the modes coherence recovered, while, simultaneously, generating a strong broadening of the THz emission spectrum.
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12
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Su TF, Huang R, Su YQ, Zhao GZ, Wu DY, Wang JA, Gong CR, Xu CL. Vibrational spectra of guaiacylglycerol-β-guaiacyl ether: experiment and theory. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2015; 139:456-463. [PMID: 25576943 DOI: 10.1016/j.saa.2014.12.052] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2014] [Revised: 12/10/2014] [Accepted: 12/12/2014] [Indexed: 06/04/2023]
Abstract
As an important inter-unit of lignin, guaiacylglycerol-β-guaiacyl (GG) ether has been synthesized, and characterized using terahertz time-domain spectroscopy in the frequency range of 5-85 cm(-1). Seven absorption peaks have been observed. Among these peaks, the 49.8 cm(-1) and 57.6 cm(-1) vibrations are propose to be characteristic absorption peaks of GG ether. Raman spectra were also measured in the range of 50-3500 cm(-1). The vibrations of the two lowest energy forms, i.e., erythro 1r4s and threo 1s4s, were calculated using density functional theory at the B3LYP/6-311G∗∗ level and assigned according to potential energy distribution. In addition, the contents of erythro and threo forms in GG sample could be estimated by comparing the waveform similarities between theoretical and observed curves in the 33.0-80.0 cm(-1) range. Results showed that the observed curve of GG sample is a combination of erythro 1s4r and threo 1s4s. The four absorption vibrations below 33.0 cm(-1) could be assigned to phonon, inter-molecular modes and/or hydrogen bond vibrations. Terahertz spectra and Raman spectra, together with theoretical calculations, could be powerful methods for predicting contents of different isomers in sample.
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Affiliation(s)
- Tong-Fu Su
- Department of Chemistry, Henan Agricultural University, Zhengzhou 450002, China
| | - Rong Huang
- Department of Chemistry, Xiamen University, Xiamen 361005, China
| | - Ya-Qiong Su
- Department of Chemistry, Xiamen University, Xiamen 361005, China
| | - Guo-Zhong Zhao
- Department of Physics, Capital Normal University, Beijing 100037, China
| | - De-Yin Wu
- Department of Chemistry, Xiamen University, Xiamen 361005, China
| | - Jian-An Wang
- College of Tobacco, Henan Agricultural University, Zhengzhou 450002, China
| | - Chang-Rong Gong
- College of Tobacco, Henan Agricultural University, Zhengzhou 450002, China
| | - Cui-Lian Xu
- Department of Chemistry, Henan Agricultural University, Zhengzhou 450002, China.
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Kondoh M, Tsubouchi M. Liquid-sheet jets for terahertz spectroscopy. OPTICS EXPRESS 2014; 22:14135-47. [PMID: 24977512 DOI: 10.1364/oe.22.014135] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
We investigated liquid-sheet jets with controllable thickness for application to terahertz (THz) spectroscopy. Slit-type and colliding-jet nozzles were used to generate optically flat liquid jets. The thickness of the liquid sheet was determined precisely by spectral interference and THz time-domain-spectroscopy methods. By adjusting the collision angle of the colliding-jet nozzle, we could control the thickness of the liquid sheet from 50 to 120 μm.
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Spectrally interleaved, comb-mode-resolved spectroscopy using swept dual terahertz combs. Sci Rep 2014; 4:3816. [PMID: 24448604 PMCID: PMC3898205 DOI: 10.1038/srep03816] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 01/02/2014] [Indexed: 02/07/2023] Open
Abstract
Optical frequency combs are innovative tools for broadband spectroscopy because a series of comb modes can serve as frequency markers that are traceable to a microwave frequency standard. However, a mode distribution that is too discrete limits the spectral sampling interval to the mode frequency spacing even though individual mode linewidth is sufficiently narrow. Here, using a combination of a spectral interleaving and dual-comb spectroscopy in the terahertz (THz) region, we achieved a spectral sampling interval equal to the mode linewidth rather than the mode spacing. The spectrally interleaved THz comb was realized by sweeping the laser repetition frequency and interleaving additional frequency marks. In low-pressure gas spectroscopy, we achieved an improved spectral sampling density of 2.5 MHz and enhanced spectral accuracy of 8.39 × 10−7 in the THz region. The proposed method is a powerful tool for simultaneously achieving high resolution, high accuracy, and broad spectral coverage in THz spectroscopy.
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Hrubesh LW, Droege MW. Pure-rotational spectrometry: a vintage analytical method applied to modern breath analysis. J Breath Res 2013; 7:037105. [PMID: 23774191 DOI: 10.1088/1752-7155/7/3/037105] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Pure-rotational spectrometry (PRS) is an established method, typically used to study structures and properties of polar gas-phase molecules, including isotopic and isomeric varieties. PRS has also been used as an analytical tool where it is particularly well suited for detecting or monitoring low-molecular-weight species that are found in exhaled breath. PRS is principally notable for its ultra-high spectral resolution which leads to exceptional specificity to identify molecular compounds in complex mixtures. Recent developments using carbon aerogel for pre-concentrating polar molecules from air samples have extended the sensitivity of PRS into the part-per-billion range. In this paper we describe the principles of PRS and show how it may be configured in several different modes for breath analysis. We discuss the pre-concentration concept and demonstrate its use with the PRS analyzer for alcohols and ammonia sampled directly from the breath.
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Yasui T, Kawamoto K, Hsieh YD, Sakaguchi Y, Jewariya M, Inaba H, Minoshima K, Hindle F, Araki T. Enhancement of spectral resolution and accuracy in asynchronous-optical-sampling terahertz time-domain spectroscopy for low-pressure gas-phase analysis. OPTICS EXPRESS 2012; 20:15071-15078. [PMID: 22772203 DOI: 10.1364/oe.20.015071] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The spectral resolution and accuracy of asynchronous-optical-sampling terahertz time-domain spectroscopy (ASOPS-THz-TDS) were evaluated by examining low-pressure gas-phase samples. Use of dual 56-MHz, erbium (Er)-doped, mode-locked femtosecond fiber lasers enhanced the spectral resolution to as low as 50.5 MHz and the spectral accuracy to as low as 6.2 × 10(-6). The results indicate that ASOPS-THz-TDS has the potential to achieve high spectral resolution, high spectral accuracy, and wide spectral coverage at the same time. ASOPS-THz-TDS will open a new door to gas-phase spectroscopy of multiple chemical species in the field of atmospheric gas analysis.
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Affiliation(s)
- Takeshi Yasui
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama, Toyonaka, Osaka 560-8531, Japan.
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Ma J, Dasgupta PK, Zelder FH, Boss GR. Cobinamide chemistries for photometric cyanide determination. A merging zone liquid core waveguide cyanide analyzer using cyanoaquacobinamide. Anal Chim Acta 2012; 736:78-84. [PMID: 22769008 DOI: 10.1016/j.aca.2012.05.028] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Revised: 05/16/2012] [Accepted: 05/17/2012] [Indexed: 11/19/2022]
Abstract
Diaquacobinamide (H(2)O)(2)Cbi(2+) or its conjugate base hydroxyaquacobinamide (OH(H(2)O)Cbi(+))) can bind up to two cyanide ions, making dicyanocobinamide. This transition is accompanied by a significant change in color, previously exploited for cyanide determination. The reagent OH(H(2)O)Cbi(+) is used in excess; when trace amounts of cyanide are added, CN(H(2)O)Cbi(+) should be formed. But the spectral absorption of CN(H(2)O)Cbi(+) is virtually the same as that of OH(H(2)O)Cbi(+). It has been inexplicable how trace amounts of cyanide are sensitively measured by this reaction. It is shown here that even with excess OH(H(2)O)Cbi(+), (CN)(2)Cbi is formed first due to kinetic reasons; this only slowly forms CN(H(2)O)Cbi(+). This understanding implies that CN(H(2)O)Cbi(+) will itself be a better reagent. We describe a single valve merging zone flow analyzer that allows both sample and reagent economy. With a 50 cm liquid core waveguide (LCW) flow cell and an inexpensive fiber optic-charge coupled device array spectrometer, a S/N=3 limit of detection of 8 nM, a linear dynamic range to 6 μM, and excellent precision (RSD 0.49% and 1.07% at 50 and 100 nM, respectively, n=5 each) are formed. At 1% carryover, sample throughput is 40 h(-1). The setup is readily used to measure thiocyanate with different reagents. We demonstrate applicability to real samples by analyzing human saliva samples and hydrolyzed extracts of apple seeds, peach pits, and almonds.
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Affiliation(s)
- Jian Ma
- Department of Chemistry and Biochemistry, University of Texas, 700 Planetarium Place, Arlington, TX 76019-0065, USA
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Doppler limited rotational transitions of OH and SH radicals measured by continuous-wave terahertz photomixing. J Mol Struct 2011. [DOI: 10.1016/j.molstruc.2011.07.055] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Medvedev IR, Neese CF, Plummer GM, De Lucia FC. Impact of atmospheric clutter on Doppler-limited gas sensors in the submillimeter/terahertz. APPLIED OPTICS 2011; 50:3028-3042. [PMID: 21691371 DOI: 10.1364/ao.50.003028] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
It is well known that clutter (spectral interference) from atmospheric constituents can be a severe limit for spectroscopic point sensors, especially where high sensitivity and specificity are required. In this paper, we will show for submillimeter/terahertz (SMM/THz) sensors that use cw electronic techniques the clutter limit for the detection of common target gases with absolute specificity (probability of false alarm ≪ 10⁻¹⁰) is in the ppt (1 part in 10¹²) range or lower. This is because the most abundant atmospheric gases are either transparent to SMM/THz radiation (e.g., CO₂) or have spectra that are very sparse relative to the 10⁵ Doppler-limited resolution elements available (e.g., H₂O). Moreover, the low clutter limit demonstrated for cw electronic systems in the SMM/THz is independent of system size and complexity.
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Affiliation(s)
- Ivan R Medvedev
- Department of Physics, Wright State University, 3640 Colonel Glenn Highway, Dayton, Ohio 45435, USA
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Yasui T, Takahashi H, Kawamoto K, Iwamoto Y, Arai K, Araki T, Inaba H, Minoshima K. Widely and continuously tunable terahertz synthesizer traceable to a microwave frequency standard. OPTICS EXPRESS 2011; 19:4428-4437. [PMID: 21369274 DOI: 10.1364/oe.19.004428] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We constructed a widely and continuously tunable terahertz frequency synthesizer traceable to a hydrogen maser linked to coordinated universal time. Photomixing of two optical frequency synthesizers, linked to the hydrogen maser via dual optical frequency combs, gave this THz synthesizer frequency uncertainty of 10⁻¹². To demonstrate the potential of wide and continuous tunability in the THz synthesizer, we tuned its output frequency up to 50 GHz discretely and 1.26 GHz continuously in the F-band while maintaining the unprecedented frequency uncertainty by using a uni-traveling-carrier photodiode as a photomixer. This THz synthesizer will be a powerful tool for broadband, high-precision THz spectroscopy and THz frequency metrology.
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Affiliation(s)
- Takeshi Yasui
- Graduate School of Engineering Science, Osaka University, Osaka, Japan.
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Mouret G, Hindle F, Cuisset A, Yang C, Bocquet R, Lours M, Rovera D. THz photomixing synthesizer based on a fiber frequency comb. OPTICS EXPRESS 2009; 17:22031-22040. [PMID: 19997448 DOI: 10.1364/oe.17.022031] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A frequency doubled erbium doped modelocked fiber frequency comb is used to implement a THz photomixing synthesizer. The useful THz linewidth is in order of 150 kHz and has been assessed along with the frequency accuracy by spectroscopic measurements demonstrating a relative accuracy of 10(-8) at frequencies around 1 THz. The THz synthesizer is used to implement a THz spectrometer to study the rotational absorption spectrum of carbonyl sulfide (OCS). Measurement of the principal transitions between 813 GHz and 1283 GHz allowed the properties of the THz spectrometer to be compared with competing techniques, and demonstrates the potential of the THz photomixing synthesizer as an alternative means to explore the THz domain.
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Affiliation(s)
- Gaël Mouret
- Université du Littoral Côte d'Opale, Laboratoire de Physico Chimie de l'Atmosphère UMR CNRS 8101, Dunkerque, France.
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Wang Y, Zhao Z, Chen Z, Zhang Y, Zhang L, Kang K. Suppression of spectral interferences due to water-vapor rotational transitions in terahertz time-domain spectroscopy. OPTICS LETTERS 2008; 33:1354-1356. [PMID: 18552956 DOI: 10.1364/ol.33.001354] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Absorption lines of atmospheric water vapor are commonly present in terahertz spectra measured in ambient air. These spectral interferences are caused by the rotational transitions of water molecules. In this study, we develop an effective method for suppression of the water-vapor effects by modeling the absorption lines using Lorentzian line shape and spectroscopic parameters extracted from the HITRAN database and then subtracting them iteratively in the frequency domain. The free-space terahertz pulse and the absorbance spectrum of an explosive material are restored successfully in the experimental verification.
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Affiliation(s)
- Yingxin Wang
- Department of Engineering Physics, Tsinghua University, Beijing, China
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Kushch I, Schwarz K, Schwentner L, Baumann B, Dzien A, Schmid A, Unterkofler K, Gastl G, Španěl P, Smith D, Amann A. Compounds enhanced in a mass spectrometric profile of smokers' exhaled breath versus non-smokers as determined in a pilot study using PTR-MS. J Breath Res 2008; 2:026002. [DOI: 10.1088/1752-7155/2/2/026002] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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