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dc.contributor.advisorFarooq, Aamir
dc.contributor.authorAlsaif, Bidoor
dc.date.accessioned2019-06-16T09:04:10Z
dc.date.available2019-06-16T09:04:10Z
dc.date.issued2019-06
dc.identifier.citationAlsaif, B. (2019). High Precision Comb-Assisted Molecular Spectroscopy in the Mid-Infrared. KAUST Research Repository. https://doi.org/10.25781/KAUST-4OR3P
dc.identifier.doi10.25781/KAUST-4OR3P
dc.identifier.urihttp://hdl.handle.net/10754/655593
dc.description.abstractIn several fields, such as biology, chemistry, combustion and environmental science, laser absorption spectroscopy represents an invaluable tool for the detection and identification of a variety of molecular species in the gas phase. For this detection to be quantitative, it is of paramount importance to rely on accurate spectroscopic parameters for the involved absorption lines in terms of line strength, line center frequency, pressure broadening, and pressure shift coefficients. The mid-infrared region offers the most favorable conditions for sensitive and chemically selective detection. The sensitivity derives from the presence of intense fundamental ro-vibrational transitions of molecules, whereas chemical selectivity relates to the unique absorption spectrum that molecules possess in the mid-IR region, thereby known as the fingerprint region. In this thesis, we combine the accelerating technology of optical frequency combs (OFC), which are powerful tools for accurate optical frequency measurements, with the wide tunability and single line emission in the mid-IR of extended cavity quantum cascade lasers (EC-QCL), to perform highly resolved, accurate and sensitive measurements in the fingerprint region, from 7.25 to 8 μm. Specifically, we have been able to lock for the first time the optical frequency of an EC-QCL to an OFC by utilizing nonlinear optics in the form of sum frequency generation (SFG) (Lamperti, AlSaif et al., 2018) and have exploited this comb-locked EC-QCL for an accurate survey of the entire ν1 ro-vibrational band of one of the most important greenhouse gases, nitrous oxide (N2O). The developed spectrometer is able to operate over a wide region of ~ 100 cm-1, in a fully automated fashion, while affording a 63 kHz uncertainty on the retrieved line center frequencies. The measurement allowed us to determine very accurately rotational constants of both ground and excited states of the ν1 band of N2O through the measurements of tens of lines of the P and R branches (AlSaif et al., JQSRT 2018). The spectrometer was then upgraded with a more recent and narrower linewidth EC-QCL to perform sub-Doppler saturated spectroscopy on the same N2O sample at a spectral resolution below 1 MHz, the sharpest ever observed with this type of laser. Finally, we worked at adding high sensitivity to the apparatus by introducing the gas in a high-finesse passive resonator and by developing a system to measure the intra-cavity absorption with cavity ring-down spectroscopy (CRDS) together with comb calibration.
dc.language.isoen
dc.subjectOptical frequency comb
dc.subjectMetrology
dc.subjectMid infrared spectroscopy
dc.subjectExtended cavity quantum cascade lasers
dc.subjectGas sensing
dc.subjectCavity ringdown spectroscopy
dc.titleHigh Precision Comb-Assisted Molecular Spectroscopy in the Mid-Infrared
dc.typeDissertation
dc.contributor.departmentComputer, Electrical and Mathematical Sciences and Engineering (CEMSE) Division
thesis.degree.grantorKing Abdullah University of Science and Technology
dc.contributor.committeememberOoi, Boon S.
dc.contributor.committeememberLiberale, Carlo
dc.contributor.committeememberMarangoni, Marco A.
thesis.degree.disciplineElectrical Engineering
thesis.degree.nameDoctor of Philosophy
refterms.dateFOA2019-06-16T09:04:11Z
kaust.request.doiyes


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