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Intracavity Laser Absorption Spectroscopy using Quantum Cascade Laser and Fabry-Perot Interferometer

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Date Issued:
2011
Abstract/Description:
Intracavity Laser Absorption Spectroscopy (ICLAS) at IR wavelengths offers an opportunity for spectral sensing of low vapor pressure compounds. We report here an ICLAS system design based on a quantum cascade laser (QCL) at THz (69.9 ?m) and IR wavelengths (9.38 and 8.1 ?m) with an open external cavity. The sensitivity of such a system is potentially very high due to extraordinarily long effective optical paths that can be achieved in an active cavity. Sensitivity estimation by numerical solution of the laser rate equations for the THz QCL ICLAS system is determined. Experimental development of the external cavity QCL is demonstrated for the two IR wavelengths, as supported by appearance of fine mode structure in the laser spectrum. The 8.1 ?m wavelength exhibits a dramatic change in the output spectrum caused by the weak intracavity absorption of acetone. Numerical solution of the laser rate equations yields a sensitivity estimation of acetone partial pressure of 165 mTorr corresponding to ~ 200 ppm. The system is also found sensitive to the humidity in the laboratory air with an absorption coefficient of just 3 x 10-7 cm-1 indicating a sensitivity of 111 ppm. Reported also is the design of a compact integrated data acquisition and control system. Potential applications include military and commercial sensing for threat compounds such as explosives, chemical gases, biological aerosols, drugs, banned or invasive organisms, bio-medical breath analysis, and terrestrial or planetary atmospheric science.
Title: Intracavity Laser Absorption Spectroscopy using Quantum Cascade Laser and Fabry-Perot Interferometer.
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Name(s): Medhi, Gautam, Author
Peale, Robert, Committee Chair
Ishigami, Marsahir, Committee Member
Chernyak, Leonid, Committee Member
Delfyett, Peter, Committee Member
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2011
Publisher: University of Central Florida
Language(s): English
Abstract/Description: Intracavity Laser Absorption Spectroscopy (ICLAS) at IR wavelengths offers an opportunity for spectral sensing of low vapor pressure compounds. We report here an ICLAS system design based on a quantum cascade laser (QCL) at THz (69.9 ?m) and IR wavelengths (9.38 and 8.1 ?m) with an open external cavity. The sensitivity of such a system is potentially very high due to extraordinarily long effective optical paths that can be achieved in an active cavity. Sensitivity estimation by numerical solution of the laser rate equations for the THz QCL ICLAS system is determined. Experimental development of the external cavity QCL is demonstrated for the two IR wavelengths, as supported by appearance of fine mode structure in the laser spectrum. The 8.1 ?m wavelength exhibits a dramatic change in the output spectrum caused by the weak intracavity absorption of acetone. Numerical solution of the laser rate equations yields a sensitivity estimation of acetone partial pressure of 165 mTorr corresponding to ~ 200 ppm. The system is also found sensitive to the humidity in the laboratory air with an absorption coefficient of just 3 x 10-7 cm-1 indicating a sensitivity of 111 ppm. Reported also is the design of a compact integrated data acquisition and control system. Potential applications include military and commercial sensing for threat compounds such as explosives, chemical gases, biological aerosols, drugs, banned or invasive organisms, bio-medical breath analysis, and terrestrial or planetary atmospheric science.
Identifier: CFE0004137 (IID), ucf:49040 (fedora)
Note(s): 2011-12-01
Ph.D.
Sciences, Physics
Doctoral
This record was generated from author submitted information.
Subject(s): Infrared -- intracavity -- spectroscopy -- quantum cascade laser -- Fabry-Perot interferometer -- external cavity -- TNT -- Fano reflector
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0004137
Restrictions on Access: public 2011-12-15
Host Institution: UCF

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