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      Transversely Excited Multipass Photoacoustic Cell Using Electromechanical Film as Microphone

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          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 (10 −9) was achieved for flowing NO 2 in N 2 at normal pressure by using the maximum of 70 laser beams between the resonator plates. The corresponding minimum detectable absorption and the normalized noise-equivalent absorption coefficients were 2.2 × 10 −7 cm −1 and 3.2 × 10 −9 cm −1WHz −1/2, respectively.

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          Most cited references27

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          ElectroMechanical Film (EMFi) — a new multipurpose electret material

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            Fiber-amplifier-enhanced photoacoustic spectroscopy with near-infrared tunable diode lasers.

            A new approach to wavelength-modulation photoacoustic spectroscopy is reported, which incorporates diode lasers in the near infrared and optical fiber amplifiers to enhance sensitivity. We demonstrate the technique with ammonia detection, yielding a sensitivity limit less than 6 parts in 10(9), by interrogating a transition near 1532 nm with 500 mW of output power from the fiber amplifier, an optical pathlength of 18.4 cm, and an integration time constant of 10 s. This sensitivity is 15 times better than in prior published results for detecting ammonia with near-infrared diode lasers. The normalized minimum detectable fractional optical density, alphaminl, is 1.8 x 10(-8); the minimum detectable absorption coefficient, alphamin, is 9.5 x 10(-10) cm(-1); and the minimum detectable absorption coefficient normalized by power and bandwidth is 1.5 x 10(-9) W cm(-1)/square root Hz. These measurements represent what we believe to be the first use of fiber amplifiers to enhance photoacoustic spectroscopy, and this technique is applicable to all other species that fall within the gain curves of optical fiber amplifiers.
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              High-sensitivity piezoelectric microphones based on stacked cellular polymer films (L)

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                Author and article information

                Journal
                Sensors (Basel)
                Sensors (Basel, Switzerland)
                Molecular Diversity Preservation International (MDPI)
                1424-8220
                2010
                26 May 2010
                : 10
                : 6
                : 5294-5307
                Affiliations
                [1 ] Optics Laboratory, Department of Physics, Tampere University of Technology, P.O. Box 692, FI-33101 Tampere, Finland; E-Mails: johan.sand@ 123456tut.fi (J.S.); tapio.sorvajarvi@ 123456tut.fi (T.S.); juha.toivonen@ 123456tut.fi (J.T.)
                [2 ] Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Air Pollution & Environmental Technology, Überlandstr. 129, 8600 Dübendorf, Switzerland; E-Mail: Albert.Manninen@ 123456empa.ch
                Author notes
                []Author to whom correspondence should be addressed; E-Mail: jaakko.saarela@ 123456tut.fi ; Tel.: +35-83-31153417; Fax: +35-83-31152600.
                Article
                sensors-10-05294-v2
                10.3390/s100605294
                3247707
                22219662
                fbb31b4a-e5bf-4f54-a7de-61fd4eca00dd
                © 2010 by the authors; licensee MDPI, Basel, Switzerland.

                This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution license ( http://creativecommons.org/licenses/by/3.0/).

                History
                : 19 April 2010
                : 21 May 2010
                : 24 May 2010
                Categories
                Article

                Biomedical engineering
                77.55.h-,photoacoustic,electromechanical film microphone,07.07.df,longitudinal resonance,82.80.kq,spectroscopy,transducer,*43.20.ks,emfit film,multipass,07.88.+y,transversal excitation,43.38.kb

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