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  • 1.
    Abd Alrahman, Chadi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Qu, Zhechao
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cavity-enhanced optical frequency comb spectroscopy of high-temperature H2O in a flame2014In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 22, no 11, p. 13889-13895Article in journal (Refereed)
    Abstract [en]

    We demonstrate near-infrared cavity-enhanced optical frequency comb spectroscopy of water in a premixed methane/air flat flame. The detection system is based on an Er:fiber femtosecond laser, a high finesse optical cavity containing the flame, and a fast-scanning Fourier transform spectrometer (FTS). High absorption sensitivity is obtained by the combination of a high-bandwidth two-point comb-cavity lock and auto-balanced detection in the FTS. The system allows recording high-temperature water absorption spectra with a resolution of 1 GHz and a bandwidth of 50 nm in an acquisition time of 0.4 s, with absorption sensitivity of 4.2 x 10 (9) cm(-1) Hz(-1/2) per spectral element.

  • 2.
    Johansson, Alexandra C.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rutkowski, Lucile
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Signal line shapes of Fourier-transform cavity-enhanced frequency modulation spectroscopy with optical frequency combs2017In: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 34, no 2, p. 358-365Article in journal (Refereed)
    Abstract [en]

    We present a thorough analysis of the signal line shapes of Fourier-transform-based noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS). We discuss the signal dependence on the ratio of the modulation frequency, f(m), to the molecular linewidth, G. We compare a full model of the signals and a simplified absorption-like analytical model that has high accuracy for low f(m)/G ratios and is much faster to compute. We verify the theory experimentally by measuring and fitting the NICE-OFCS spectra of CO2 at 1575 nm using a system based on an Er: fiber femtosecond laser and a cavity with a finesse of similar to 11000. 

  • 3.
    Johansson, Alexandra C.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Westberg, Jonas
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rutkowski, Lucile
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wysocki, Gerard
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Faraday Rotation Spectroscopy Using an Optical Frequency Comb2017In: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    Summary form only given. The mid-infrared (MIR) part of the optical spectrum (3-12 μm) houses the fundamental absorption bands of a multitude of environmentally important molecules, but the abundance of water absorption often causes interference with the target species and makes concentration measurement inaccurate. The broad spectral coverage of optical frequency comb spectroscopy (OFCS) provides access to entire ro-vibrational bands and allows more accurate concentration quantification and retrieval of sample temperature. To further improve detection sensitivity of paramagnetic species in the presence of interfering species, we combine a MIR optical frequency comb with the Faraday rotation spectroscopy (FRS) technique [I], which is insensitive to interferences from diamagnetic molecules, such as H 2 O, CO 2 , and CO. In FRS, the rotation of the polarization induced by an external magnetic field in the vicinity of paramagnetic molecular transitions is translated to an intensity change by the use of a polarization analyzer, which effectively removes the influence of any non-paramagnetic species. In the proof of principle demonstration of OFC-FRS we detect nitric oxide (NO) in the presence of water at 5.3 μm using a Fourier transform spectrometer.

  • 4.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fourier transform and Vernier spectroscopy using optical frequency combs2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Optical frequency comb spectroscopy (OFCS) combines two previously exclusive features, i.e., wide optical bandwidth and high spectral resolution, enabling precise measurements of entire molecular bands and simultaneous monitoring of multiple gas species in a short measurement time. Moreover, the equidistant mode structure of frequency combs enables efficient coupling of the comb power to enhancement resonant cavities, yielding high detection sensitivities. Different broadband detection methods have been developed to exploit the full potential of frequency combs in spectroscopy, based either on Fourier transform spectroscopy or on dispersive elements.There have been two main aims of the research presented in this thesis. The first has been to improve the performance of mechanical Fourier transform spectrometers (FTS) based on frequency combs in terms of sensitivity, resolution and spectral coverage. In pursuit of this aim, we have developed a new spectroscopic technique, so-called noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS), and achieved a shot-noise-limited sensitivity and low ppb (parts-per-billion, 10−9) CO2 concentration detection limit in the near-infrared range using commercially available components. We have also realized a novel method for acquisition and analysis of comb-based FTS spectra, a so-called sub-nominal resolution method, which provides ultra-high spectral resolution and frequency accuracy (both in kHz range, limited only by the stability of the comb) over the broadband spectral range of the frequency comb. Finally, we have developed an optical parametric oscillator generating a frequency comb in the mid-infrared range, where the strongest ro-vibrational molecular absorption lines reside. Using this mid-infrared comb and an FTS, we have demonstrated, for the first time, comb spectroscopy above 5 μm, measured broadband spectra of several species and reached low ppb detection limits for CH4, NO and CO in 1 s.The second aim has been more application-oriented, focused on frequency comb spectroscopy in combustion environments and under atmospheric conditions for fast and sensitive multispecies detection. We have demonstrated, for the first time, cavity-enhanced optical frequency comb spectroscopy in a flame, detected broadband high temperature H2O and OH spectra using the FTS in the near-infrared range and showed the potential of the technique for flame thermometry. For applications demanding a short measurement time and high sensitivity under atmospheric pressure conditions, we have implemented continuous-filtering Vernier spectroscopy, a dispersion-based spectroscopic technique, for the first time in the mid-infrared range. The spectrometer was sensitive, fast, robust, and capable of multispecies detection with 2 ppb detection limit for CH4 in 25 ms.

  • 5.
    Khodabakhsh, Amir
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Abd Alrahman, Chadi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Noise-immune cavity-enhanced optical frequency comb spectroscopy2014In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 39, no 17, p. 5034-5037Article in journal (Refereed)
    Abstract [en]

    We present a new method of optical frequency comb spectroscopy that combines cavity enhancement with frequency modulation to obtain immunity to laser frequency-to-amplitude noise conversion by the cavity modes and, thus, high absorption sensitivity over a broad spectral range. A frequency comb is locked to a cavity with a free spectral range (FSR) equal to 4/3 times the repetition rate of the laser, and phase-modulated at a frequency equal to the cavity FSR. The transmitted light is analyzed by a Fourier transform spectrometer with a high bandwidth detector. Phase-sensitive detection of the interferogram yields a noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS) signal. In the first demonstration, we record NICE-OFCS signals from the overtone CO2 band at 1575 nm with absorption sensitivity of 4.3 x 10(-10) cm(-1) Hz(-1/2) per spectral element, close to the shot noise limit.

  • 6.
    Khodabakhsh, Amir
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Badarla, Venkata R.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rutkowski, Lucile
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lee, Kevin F.
    Jiang, J.
    Mohr, C.
    Fermann, Martin E.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Optical Frequency Comb Spectroscopy at 3.3 and 5.2 mu m by a Tm:fiber-Laser-Pumped Optical Parametric Oscillator2016In: Proceedings Conference on Lasers and Electro-Optics, 2016Conference paper (Refereed)
    Abstract [en]

    Using a doubly-resonant femtosecond optical parametric oscillator in combination with a multipass cell and a Fourier transform spectrometer we measure broadband CH4 and NO absorption spectra at fundamental transition wavelengths.

  • 7.
    Khodabakhsh, Amir
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Noise-immune cavity-enhanced optical frequency comb spectroscopy: a sensitive technique for high-resolution broadband molecular detection2015In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 119, no 1, p. 87-96Article in journal (Refereed)
    Abstract [en]

    Noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS) is a recently developed technique that utilizes phase modulation to obtain immunity to frequency-to-amplitude noise conversion by the cavity modes and yields high absorption sensitivity over a broad spectral range. We describe the principles of the technique and discuss possible comb-cavity matching solutions. We present a theoretical description of NICE-OFCS signals detected with a Fourier transform spectrometer (FTS) and validate the model by comparing it to experimental CO2 spectra around 1,575 nm. Our system is based on an Er:fiber femtosecond laser locked to a cavity and phase-modulated at a frequency equal to a multiple of the cavity free spectral range (FSR). The NICE-OFCS signal is detected by a fast-scanning FTS equipped with a high-bandwidth commercial detector. We demonstrate a simple method of passive locking of the modulation frequency to the cavity FSR that significantly improves the long-term stability of the system, allowing averaging times on the order of minutes. Using a cavity with a finesse of ~9,000, we obtain absorption sensitivity of 6.4 × 10−11 cm−1 Hz−1∕2 per spectral element and concentration detection limit for CO2 of 450 ppb Hz−1/2, determined by multiline fitting.

  • 8.
    Khodabakhsh, Amir
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rutkowski, Lucile
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fourier-Transform-Based Noise-Immune Cavity-Enhanced Optical Frequency Comb Spectroscopy2015In: 2015 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), 2015Conference paper (Refereed)
    Abstract [en]

    We achieve absorption sensitivity of 6.4 x 10(-11) cm(-1) Hz(-1/2) per spectral element with near-infrared Fourier-transform-based noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS), which allows detection of CO2 at ppb concentration levels.

  • 9.
    Khodabakhsh, Amir
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Qu, Zhechao
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Abd Alrahman, Chadi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rutkowski, Lucile
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cavity-Enhanced Optical Frequency Comb Spectroscopy of High-Temperature Water in a Flame2015In: 2015 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), 2015Conference paper (Refereed)
    Abstract [en]

    We demonstrate detection of broadband high-temperature water spectra in a laminar, premixed methane/air flat flame using high-resolution near-infrared cavity-enhanced optical frequency comb spectroscopy incorporating a fast-scanning Fourier transform spectrometer.

  • 10.
    Khodabakhsh, Amir
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ramaiah-Badarla, Venkata
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rutkowski, Lucile
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lee, Kevin F.
    Jiang, Jie
    Mohr, Christian
    Fermann, Martin E.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fourier transform and Vernier spectroscopy using an optical frequency comb at 3-5.4 μm2016In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 41, no 11, p. 2541-2544Article in journal (Refereed)
    Abstract [en]

    We present a versatilemid-infrared frequency comb spectroscopy system based on a doubly resonant optical parametric oscillator tunable in the 3-5.4 mu m range and two detection methods: a Fourier transform spectrometer (FTS) and a continuous-filtering Vernier spectrometer (CF-VS). Using the FTS with a multipass cell, we measure high precision broadband absorption spectra of CH4 at 3.3 mu m and NO at 5.25 mu m, the latter for the first time with comb spectroscopy, and we detect atmospheric species (CH4, CO, CO2, and H2O) in air in the signal and idler ranges. Multiline fitting yields minimum detectable concentrations of 10-20 ppbHz-1/2 for CH4, NO, and CO. For the first time in the mid-infrared, we perform CF-VS using an enhancement cavity, a grating, and a single detector, and we measure the absorption spectrum of CH4 and H2O in ambient air at similar to 3.3 m mu, reaching a 40 ppb concentration detection limit for CH4 in 2 ms. 

  • 11.
    Khodabakhsh, Amir
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rutkowski, Lucile
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Morville, Jerome
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Soboń, Grzegorz
    Umeå University, Faculty of Science and Technology, Department of Physics. Faculty of Electronics, Wrocław University of Science and Technology, Wrocław, Poland.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cavity-Enhanced Continuous-Filtering Vernier Spectroscopy at 3.3 mu m using a Femtosecond Optical Parametric Oscillator2017In: 2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC), IEEE , 2017, p. CH_2_2-Conference paper (Refereed)
    Abstract [en]

    Optical frequency comb spectroscopy in the mid-infrared fingerprint region combines broad spectral bandwidth with high detection sensitivity and allows simultaneous detection of trace amounts of many molecular species. We have recently demonstrated a continuous-filtering Vernier spectrometer based on a mid-infrared optical frequency comb and an enhancement cavity for fast and sensitive detection of CH4 [1]. Here we present an improved, fully automatized and frequency calibrated continuous-filtering Vernier spectrometer, schematically shown in Fig. 1(a). The comb source is a doubly resonant optical parametric oscillator (DROPO) based on an orientation-patterned GaAs crystal synchronously pumped by a Tm:fiber femtosecond laser (125 MHz repetition rate, frep). The signal comb (3.1–3.4 µm, 30 mW) is mode matched to a 60-cm long Vernier enhancement cavity with a finesse of ~350 at 3.25 μm, placed in an enclosure that can be filled with the gas sample. The output mirror is attached to a PZT and mounted on a translation stage. When the cavity free spectral range is perfectly matched to twice the frep (250 MHz) every other signal comb mode is transmitted through the cavity. By detuning the cavity length from this perfect match position the cavity resonances act as a filter and transmit groups of comb modes called Vernier orders [2]. A diffraction grating mounted on a galvo-scanner separates these orders after the cavity and the chosen order is sent to the detection system. The Vernier order is tuned across the signal comb spectrum by scanning the cavity length (at 20 Hz) and the grating is rotated synchronously to fix the order in space and allow acquisition of the entire spectrum in 25 ms. Any residual mismatch between the cavity length scan and the grating rotation is compensated by a feedback loop acting on the frep of the pump laser and the PZT of the Vernier cavity [2]. A Fabry-Perot etalon is used for frequency calibration of the spectrometer. Figure 1(b) shows in black the normalized transmission spectrum of a sample containing 5.0 ppm CH4 and 160 ppm water. The red and blue curves show the corresponding fit of the Vernier spectrum [3] of CH4 and water, respectively, calculated using Voigt profiles, line parameters from the HITRAN database, and the experimentally determined cavity finesse. The figure of merit of the spectrometer is 1×10−9cm−1 Hz−1∕2 per spectral element and multiline fitting yields minimum detectable concentration of CH4 of 2 ppb in 25 ms, translating into 400 ppt Hz−1∕2 Since the spectrum of the signal comb covers the fundamental C-H stretch transitions we expect low detection limits for other hydrocarbons as well. In conclusion, mid-infrared comb-based continuous-filtering Vernier spectroscopy allows fast and highly sensitive measurement of broadband absorption spectra using a robust and compact detection system.

  • 12.
    Khodabakhsh, Amir
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rutkowski, Lucile
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Morville, Jérôme
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mid-infrared continuous-filtering Vernier spectroscopy using a doubly resonant optical parametric oscillator2017In: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 123, no 210Article in journal (Refereed)
    Abstract [en]

    We present a continuous-filtering Vernier spectrometer operating in the 3.15-3.4 mu m range, based on a femtosecond doubly resonant optical parametric oscillator, a cavity with a finesse of 340, a grating mounted on a galvo scanner, and two photodiodes. The spectrometer allows acquisition of one spectrum spanning 250 nm of bandwidth in 25 ms with 8 GHz resolution, sufficient to detect molecular lines at atmospheric pressure. An active lock ensures good frequency and intensity stability of the consecutive spectra and enables continuous signal acquisition and efficient averaging. The relative frequency scale is calibrated using a Fabry-Perot etalon or, alternatively, the galvo scanner position signal. We measure spectra of a calibrated CH4 gas sample as well as dry and laboratory air and extract CH4 and -H2O concentrations by multiline fitting of model spectra. The figure of merit of the spectrometer is 1.7 x 10(-9) cm(-1) Hz(-1/2) per spectral element and the minimum detectable concentration of CH4 is 360 ppt Hz(-1/2), averaging down to 90 ppt after 16 s.

  • 13.
    Khodabakhsh, Amir
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Rutkowski, Lucile
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Morville, Jérôme
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Soboń, Grzegorz
    Umeå University, Faculty of Science and Technology, Department of Physics. Faculty of Electronics, Wrocław University of Science and Technology, Wrocław, Poland.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Continuous-Filtering Vernier Spectroscopy at 3.3 mu m Using a Femtosecond Optical Parametric Oscillator2017In: 2017 conference on lasers and elecro-optics (CLEO): Science and innovations, IEEE , 2017, article id SW1L.5Conference paper (Refereed)
    Abstract [en]

    Using a cavity-enhanced continuous-filtering Vernier spectrometer based on a femtosecond optical parametric oscillator we measure broadband spectra of atmospheric water and CH4 around 3.3 mu m reaching 4 ppb detection limit for CH4 in 15 ms.

  • 14. Maslowski, P.
    et al.
    Kowzan, G.
    Charczun, D.
    Lisak, D.
    Trawinski, R.
    Rutkowski, Lucile
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lee, K. F.
    Fermann, M. E.
    Optical Frequency Comb Spectroscopy for Gas Metrology and Trace Gas Detection2017In: 2017 Conference on lasers and electro-optics (CLEO), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    We report recent developments of comb-based broadband absorption spectroscopy. The comb-line resolving approaches and Fourier transform spectroscopy with sub-nominal resolution overcome the frequency resolution limits of conventional techniques. Advantages for various applications will be discussed.

  • 15. Maslowski, Piotr
    et al.
    Lee, Kevin F.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kowzan, Grzegorz
    Rutkowski, Lucile
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mills, Andrew A.
    Mohr, Christian
    Jiang, Jie
    Fermann, Martin E.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Surpassing the path-limited resolution of Fourier-transform spectrometry with frequency combs2016In: Physical Review A, ISSN 2469-9926, Vol. 93, no 2, article id 021802Article in journal (Refereed)
    Abstract [en]

    We overcome the resolution limit of Fourier-transform spectrometry and measure instrumental line-shape-free broadband molecular spectra with lines narrower than the optical path-limited resolution. We do this by using an optical frequency comb and precisely matching the maximum delay range of the spectrometer to the comb line spacing to measure the intensities of the individual comb lines. This method allows measurements of undistorted high-resolution spectra with acquisition time and interferometer length reduced by orders of magnitude and with frequency scale accuracy given by the comb.

  • 16.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Broadband and High Resolution Direct Measurement of Cavity Resonances2017In: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    Summary form only given. Optical frequency combs offer unprecedented combination of broad bandwidth and high resolution and their coupling to enhancement cavities provides high sensitivity for spectroscopic measurements. Here we use a frequency-comb-based Fourier transform spectrometer (FTS) to measure the narrow resonances of a high-finesse cavity over a bandwidth of 100 nm around 1.55 μm and derive the group delay dispersion (GDD) of the cavity mirrors with precision below 1 fs 2 from the cavity resonance frequencies. We do this using a method that allows precise sampling of the comb intensities using an FTS with nominal resolution matched to the comb repetition rate (f rep ) [1, 2], and we demonstrate that sub-MHz resolution is achieved.

  • 17.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mechanical Fourier Transform Spectrometer with kHz Resolution2017In: 2017 conference on lasers and electro-optics (CLEO): Science and innovations, IEEE, 2017, article id SW4J.6Conference paper (Refereed)
    Abstract [en]

    We measure simultaneously 11000 resonances of a high-finesse cavity with kHz level resolution using optical frequency comb Fourier transform spectroscopy and retrieve the dispersion of the cavity mirrors from the cavity mode spacing.

  • 18.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Maslowski, Piotr
    Kowzan, Grzegorz
    Lee, Kevin F.
    Mills, Andrew A.
    Mohr, Christian
    Jiang, Jie
    Fermann, Martin E.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Optical Frequency Comb Fourier Transform Spectroscopy with Resolution beyond the Path Difference Limit2016In: Proceedings Conference on Lasers and Electro-Optics Part of CLEO: 2016 5–10 June 2016, San Jose, California, United States, 2016Conference paper (Refereed)
    Abstract [en]

    We overcome the resolution limit of Fourier transform spectrometry and measure instrumental-lineshape-free high-resolution broadband molecular spectra by matching the spectrometer's optical path difference to the line spacing of an optical frequency comb.

  • 19.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Valiev, Damir
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lodi, Lorenzo
    Yurchenko, Sergey
    Polyansky, Oleg L.
    Tennyson, Jonathan
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Detection of OH and H2O in an Atmospheric Flame by Near-Infrared Optical Frequency Comb Spectroscopy2017In: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2017Conference paper (Refereed)
    Abstract [en]

    Absorption spectroscopy is attractive for combustion diagnostics because it allows in-situ and calibration-free quantification of reactants/products and thermometry. However, spectra measured at atmospheric pressure in the near-infrared telecom range, where laser sources and optical components are readily available, suffer from strong water interference. Cavity-enhanced optical frequency comb spectroscopy (CE-OFCS) is well suited for detection of other species, as it provides broad bandwidth with high signal-to-noise ratio and resolution, and allows de-convolving the spectra hidden among water transitions. Here we report detection of OH in the presence of H2O in an atmospheric premixed methane/air flat flame by CE-OFCS at 1.57 μm. We demonstrate a new water line list that is more accurate than HITEMP [1] and we isolate the OH lines by dividing spectra taken at different heights above the burner (HABs) to retrieve OH concentration and flame temperature.

  • 20.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Valiev, Damir
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tkacz, Arkadiusz
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Detection of OH in an atmospheric flame at 1.5 μm using optical frequency comb spectroscopy2016In: Photonics Letters of Poland, ISSN 2080-2242, E-ISSN 2080-2242, Vol. 8, no 4, p. 110-112Article in journal (Refereed)
    Abstract [en]

    We report broadband detection of OH in a premixed CH4/air flat flame at atmospheric pressure using cavity-enhanced absorption spectroscopy based on an Er:fiber femtosecond laser and a Fourier transform spectrometer. By taking ratios of spectra measured at different heights above the burner we separate twenty OH transitions from the largely overlapping water background. We retrieve from fits to the OH lines the relative variation of OH concentration and flame temperature with a height above the burner and compare them with the 1D simulations of flame structure.

  • 21.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zhao, Gang
    Umeå University, Faculty of Science and Technology, Department of Physics. State Key Laboratory of Quantum Optics and Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China.
    Hausmaninger, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sensitive and broadband measurement of dispersion in a cavity using a Fourier transform spectrometer with kHz resolution2017In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, no 18, p. 21711-21718Article in journal (Refereed)
    Abstract [en]

    Optical cavities provide high sensitivity to dispersion since their resonance frequencies depend on the index of refraction. We present a direct, broadband, and accurate measurement of the modes of a high finesse cavity using an optical frequency comb and a mechanical Fourier transform spectrometer with a kHz-level resolution. We characterize 16000 longitudinal cavity modes spanning 16 THz of bandwidth in terms of center frequency, linewidth, and amplitude. Using the center frequencies we retrieve the group delay dispersion of the cavity mirror coatings and pure N2 with 0.1 fs2 precision and 1 fs2 accuracy, as well as the refractivity of the 3ν13 absorption band of CO2 with 5 × 10‒12 precision. This opens up for broadband refractive index metrology and calibration-free spectroscopy of entire molecular bands.

  • 22.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zhao, Gang
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hausmaninger, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Axner, Ove
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Broadband cavity characterization using a Fourier transform spectrometer with kHz resolutionIn: Optica, ISSN 2334-2536Article in journal (Refereed)
  • 23.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Valiev, Damir M.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lodi, Lorenzo
    Qu, Zhechao
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ghorbani, Ramin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Polyansky, Oleg L.
    Jin, Yuwei
    Tennyson, Jonathan
    Schmidt, Florian M.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Measurement of H2O and OH in a Flame by Optical Frequency Comb Spectroscopy2016In: Proceedings Conference on Lasers and Electro-Optics, 2016Conference paper (Refereed)
    Abstract [en]

    We measure broadband H2O and OH spectra in a flame using near-infrared cavity-enhanced Fourier transform optical frequency comb spectroscopy, we retrieve temperature and OH concentration, and compare water spectra to an improved line list.

  • 24.
    Rutkowski, Lucile
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Masłowski, Piotr
    Johansson, Alexandra C.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Optical frequency comb Fourier transform spectroscopy with sub-nominal resolution and precision beyond the Voigt profile2018In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 204, p. 63-73Article in journal (Refereed)
    Abstract [en]

    Broadband precision spectroscopy is indispensable for providing high fidelity molecular parameters for spectroscopic databases. We have recently shown that mechanical Fourier transform spectrometers based on optical frequency combs can measure broadband high-resolution molecular spectra undistorted by the instrumental line shape (ILS) and with a highly precise frequency scale provided by the comb. The accurate measurement of the power of the comb modes interacting with the molecular sample was achieved by acquiring single-burst interferograms with nominal resolution matched to the comb mode spacing. Here we describe in detail the experimental and numerical steps needed to achieve sub-nominal resolution and retrieve ILS-free molecular spectra, i.e. with ILS-induced distortion below the noise level. We investigate the accuracy of the transition line centers retrieved by fitting to the absorption lines measured using this method. We verify the performance by measuring an ILS-free cavity-enhanced low-pressure spectrum of the 3ν1 + ν3 band of CO2 around 1575 nm with line widths narrower than the nominal resolution. We observe and quantify collisional narrowing of absorption line shape, for the first time with a comb-based spectroscopic technique. Thus retrieval of line shape parameters with accuracy not limited by the Voigt profile is now possible for entire absorption bands acquired simultaneously.

  • 25. Rutkowski, Lucile
    et al.
    Masłowski, Piotr
    Johansson, Alexandra
    Khodabakhsh, Amir
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Foltynowicz, Aleksandra
    Optical Frequency Comb Fourier Transform Spectroscopy with Sub-Nominal Resolution - Principles and ImplementationIn: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352Article in journal (Refereed)
1 - 25 of 25
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