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  • 1.
    Ehlers, Patrick
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Use of etalon-immune distances to reduce the influence of background signals in frequency-modulation spectroscopy and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy2014Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 31, nr 12, s. 2938-2945Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The detection sensitivity of phase-modulated techniques such as frequency-modulation spectroscopy (FMS) and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is often limited by etalon background signals. It has previously been shown that the impact of etalons can be reduced by the use of etalon-immune distances (EIDs), i.e., by separating the surfaces that give rise to etalons by a distance of q. L-m, where L-m is given by c/2n nu(m), where, in turn, n and nu(m) are the index of refraction between the components that make up the etalon (thus most often that of air) and the modulation frequency, respectively, and where q is an integer (i.e., 1, 2, 3,.) or half-integer (i.e., 1/2, 1, 3/2,.) for the dispersion and absorption modes of detection, respectively. An etalon created by surfaces separated by an EID will evade detection and thereby not contribute to any background signal. The concept of EIDs in FMS and NICE-OHMS is in this work demonstrated, scrutinized, and discussed in some detail. It is shown that the influence of EIDs on the absorption and dispersion modes of detection is significantly different; signals detected at the dispersion phase are considerably less sensitive to deviations from exact EID conditions than those detected at the absorption phase. For example, the FM background signal from an etalon whose length deviates from an EID by 2.5% of L-m (e.g., by 1 cm for an L-m of 40 cm), detected in dispersion, is only 9% of that in absorption. This makes the former mode of detection the preferred one whenever a sturdy immunity against etalons is needed or when optical components with parallel surfaces (e.g., lenses, polarizers, or beam splitters) are used. The impact of the concept of EIDs on NICE-OHMS is demonstrated by the use of Allan-Werle plots.

  • 2.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Optical Frequency Comb Fourier Transform Spectroscopy2018Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Fourier transform spectroscopy (FTS) based on optical frequency combs is an excellent spectroscopic tool as it provides broadband molecular spectra with high spectral resolution and an absolutely calibrated frequency scale. Moreover, the equidistant comb mode structure enables efficient coupling of the comb to enhancement cavities, yielding high detection sensitivity. This thesis focuses on further advances in comb-based FTS to improve its performance and extend its capabilities for broadband precision spectroscopy, particularly in terms of i) spectral resolution, ii) accuracy and precision of molecular parameters as well as concentrations retrieved from fitting models to spectra, and iii) species selectivity.

    To improve the spectral resolution we developed a new methodology to acquire and analyze comb-based FTS signals that yields spectra with a resolution limited by the comb linewidth rather than the optical path difference of the FTS, referred to as the sub-nominal resolution method. This method enables measurements of narrow features, e.g. low-pressure absorption spectra and modes of enhancement cavities, with frequency scale accuracy and precision provided by the comb. Using the technique we measured low-pressure spectra of the entire 3ν13 carbon dioxide (CO2) band at 1575 nm with sufficient signal-to-noise ratio and precision to observe collision narrowing of the absorption lineshape, which was for the first time with a comb-based spectroscopic technique. This allowed retrieval of spectral line parameters for this CO2 band using the speed-dependent Voigt profile.

    Using the sub-nominal resolution method, we measured the transmission modes of a Fabry-Perot cavity over 15 THz of bandwidth with kHz resolution and characterized the cavity modes in terms of their center frequency, linewidth, and amplitude. From the mode center frequencies, we retrieved the group delay dispersion of cavity mirror coatings and intracavity gas with an unprecedented combination of spectral bandwidth and resolution. By measuring both the mode broadening and frequency shift simultaneously we performed broadband cavity-enhanced complex refractive index spectroscopy (CE-CRIS), which allows for simultaneous and calibration-free assessment of the absorption and dispersion spectra of intracavity gas. In this first demonstration we measured the absorption and dispersion spectra of three combination bands of CO2 in the 1525 to 1620 nm range.

    Another comb-based FTS technique is noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS), which combines phase modulation and cavity-enhancement to obtain broadband and highly sensitive absorption spectra. In this thesis we improved the NICE-OFCS technique in terms of stability, sensitivity and modeling of the NICE-OFCS signal. We implemented a model of the NICE-OFCS signal with multiline fitting for assessment of gas concentration. We also identified the optimum operating conditions of the NICE-OFCS systems for accurate gas concentration assessment.

    Finally, to improve the species selectivity we combined comb-based FTS with the Faraday rotation spectroscopy (FRS) technique. In this first demonstration of optical frequency comb Faraday rotation spectroscopy (OFC-FRS), we measured background and interference-free spectra of the entire Q- and R-branches of the fundamental vibrational band of nitric oxide at 5.3 μm showing good agreement with the theoretical model.

  • 3.
    Johansson, Alexandra C.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Filipsson, Anna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Maslowski, Piotr
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    CO2 Line Parameter Retrieval Beyond the Voigt Profile Using Comb-Based Fourier Transform Spectroscopy2018Ingår i: Conference on Lasers and Electro-Optics, Optical Society of America, 2018Konferensbidrag (Refereegranskat)
    Abstract [en]

    We measure absorption spectra of the CO213 band at 1.57 μm using optical frequency comb Fourier transform spectroscopy with sub-nominal resolution and retrieve line shape parameters using multiline fitting with the speed-dependent Voigt profile.

  • 4.
    Johansson, Alexandra C.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Filipsson, Anna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hausmaninger, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zhao, Gang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. 2 State Key Laboratory of Quantum Optics and Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Broadband calibration-free cavity-enhanced complex refractive index spectroscopy using a frequency comb2018Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 26, nr 16, s. 20633-20648Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present broadband cavity-enhanced complex refractive index spectroscopy (CE-CRIS), a technique for calibration-free determination of the complex refractive index of entire molecular bands via direct measurement of transmission modes of a Fabry-Perot cavity filled with the sample. The measurement of the cavity transmission spectrum is done using an optical frequency comb and a mechanical Fourier transform spectrometer with sub-nominal resolution. Molecular absorption and dispersion spectra (corresponding to the imaginary and real parts of the refractive index) are obtained from the cavity mode broadening and shift retrieved from fits of Lorentzian profiles to the individual cavity modes. This method is calibration-free because the mode broadening and shift are independent of the cavity parameters such as the length and mirror reflectivity. In this first demonstration of broadband CE-CRIS we measure simultaneously the absorption and dispersion spectra of three combination bands of CO2 in the range between 1525 nm and 1620 nm and achieve good agreement with theoretical models. This opens up for precision spectroscopy of the complex refractive index of several molecular bands simultaneously. 

  • 5.
    Johansson, Alexandra C.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Signal line shapes of Fourier-transform cavity-enhanced frequency modulation spectroscopy with optical frequency combs2017Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 34, nr 2, s. 358-365Artikel i tidskrift (Refereegranskat)
    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. 

  • 6.
    Johansson, Alexandra C.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Westberg, Jonas
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wysocki, Gerard
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Faraday Rotation Spectroscopy Using an Optical Frequency Comb2017Ingår i: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2017Konferensbidrag (Refereegranskat)
    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.

  • 7.
    Johansson, Alexandra C.
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Westberg, Jonas
    Wysocki, Gerard
    Foltynowicz, Aleksandra
    Optical frequency comb Faraday rotation spectroscopy2018Ingår i: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 124, nr 5, artikel-id 79Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate optical frequency comb Faraday rotation spectroscopy (OFC-FRS) for broadband interference-free detection of paramagnetic species. The system is based on a femtosecond doubly resonant optical parametric oscillator and a fast-scanning Fourier transform spectrometer (FTS). The sample is placed in a DC magnetic field parallel to the light propagation. Efficient background suppression is implemented via switching the direction of the field on consecutive FTS scans and subtracting the consecutive spectra, which enables long-term averaging. In this first demonstration, we measure the entire Q- and R-branches of the fundamental band of nitric oxide in the 5.2–5.4 μm range and achieve good agreement with a theoretical model.

  • 8.
    Khodabakhsh, Amir
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Badarla, Venkata R.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Lee, Kevin F.
    Jiang, J.
    Mohr, C.
    Fermann, Martin E.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Optical Frequency Comb Spectroscopy at 3.3 and 5.2 mu m by a Tm:fiber-Laser-Pumped Optical Parametric Oscillator2016Ingår i: Proceedings Conference on Lasers and Electro-Optics, 2016Konferensbidrag (Refereegranskat)
    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.

  • 9.
    Khodabakhsh, Amir
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Noise-immune cavity-enhanced optical frequency comb spectroscopy: a sensitive technique for high-resolution broadband molecular detection2015Ingår i: Applied physics. B, Lasers and optics (Print), ISSN 0946-2171, E-ISSN 1432-0649, Vol. 119, nr 1, s. 87-96Artikel i tidskrift (Refereegranskat)
    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.

  • 10.
    Khodabakhsh, Amir
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Fourier-Transform-Based Noise-Immune Cavity-Enhanced Optical Frequency Comb Spectroscopy2015Ingår i: 2015 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), 2015Konferensbidrag (Refereegranskat)
    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.

  • 11.
    Khodabakhsh, Amir
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Qu, Zhechao
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Abd Alrahman, Chadi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Schmidt, Florian M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Cavity-Enhanced Optical Frequency Comb Spectroscopy of High-Temperature Water in a Flame2015Ingår i: 2015 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO), 2015Konferensbidrag (Refereegranskat)
    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.

  • 12.
    Khodabakhsh, Amir
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ramaiah-Badarla, Venkata
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Lee, Kevin F.
    Jiang, Jie
    Mohr, Christian
    Fermann, Martin E.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Fourier transform and Vernier spectroscopy using an optical frequency comb at 3-5.4 μm2016Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 41, nr 11, s. 2541-2544Artikel i tidskrift (Refereegranskat)
    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. 

  • 13.
    Khodabakhsh, Amir
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Morville, Jerome
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Soboń, Grzegorz
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Faculty of Electronics, Wrocław University of Science and Technology, Wrocław, Poland.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Cavity-Enhanced Continuous-Filtering Vernier Spectroscopy at 3.3 mu m using a Femtosecond Optical Parametric Oscillator2017Ingår i: 2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC), IEEE , 2017, s. CH_2_2-Konferensbidrag (Refereegranskat)
    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.

  • 14.
    Khodabakhsh, Amir
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Morville, Jérôme
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Soboń, Grzegorz
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Faculty of Electronics, Wrocław University of Science and Technology, Wrocław, Poland.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Continuous-Filtering Vernier Spectroscopy at 3.3 mu m Using a Femtosecond Optical Parametric Oscillator2017Ingår i: 2017 conference on lasers and elecro-optics (CLEO): Science and innovations, IEEE , 2017, artikel-id SW1L.5Konferensbidrag (Refereegranskat)
    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.

  • 15. Maslowski, P.
    et al.
    Kowzan, G.
    Charczun, D.
    Lisak, D.
    Trawinski, R.
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Lee, K. F.
    Fermann, M. E.
    Optical Frequency Comb Spectroscopy for Gas Metrology and Trace Gas Detection2017Ingår i: 2017 Conference on lasers and electro-optics (CLEO), IEEE, 2017Konferensbidrag (Refereegranskat)
    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.

  • 16. Maslowski, Piotr
    et al.
    Lee, Kevin F.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Kowzan, Grzegorz
    Rutkowski, Lucile
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Mills, Andrew A.
    Mohr, Christian
    Jiang, Jie
    Fermann, Martin E.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Surpassing the path-limited resolution of Fourier-transform spectrometry with frequency combs2016Ingår i: Physical Review A, ISSN 2469-9926, Vol. 93, nr 2, artikel-id 021802Artikel i tidskrift (Refereegranskat)
    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.

  • 17.
    Rutkowski, Lucile
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Schmidt, Florian M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Khodabakhsh, Amir
    Kyuberis, Aleksandra A.
    Zobov, Nikolai F.
    Polyansky, Oleg L.
    Yurchenko, Sergei N.
    Tennyson, Jonathan
    An experimental water line list at 1950 K in the 6250–6670 cm−1 region2018Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 205, s. 213-219Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An absorption spectrum of (H2O)-O-16 at 1950 K is recorded in a premixed methane/air flat flame using a cavity-enhanced optical frequency comb-based Fourier transform spectrometer. 2417 absorption lines are identified in the 6250-6670 cm(-1) region with an accuracy of about 0.01 cm(-1). Absolute line intensities are retrieved using temperature and concentration values obtained by tunable diode laser absorption spectroscopy. Line assignments are made using a combination of empirically known energy levels and predictions from the new POKAZATEL variational line list. 2030 of the observed lines are assigned to 2937 transitions, once blends are taken into account. 126 new energy levels of (H2O)-O-16 are identified. The assigned transitions belong to 136 bands and span rotational states up to J = 27.

  • 18.
    Rutkowski, Lucile
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Broadband and High Resolution Direct Measurement of Cavity Resonances2017Ingår i: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2017Konferensbidrag (Refereegranskat)
    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.

  • 19.
    Rutkowski, Lucile
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Mechanical Fourier Transform Spectrometer with kHz Resolution2017Ingår i: 2017 conference on lasers and electro-optics (CLEO): Science and innovations, IEEE, 2017, artikel-id SW4J.6Konferensbidrag (Refereegranskat)
    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.

  • 20.
    Rutkowski, Lucile
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Maslowski, Piotr
    Kowzan, Grzegorz
    Lee, Kevin F.
    Mills, Andrew A.
    Mohr, Christian
    Jiang, Jie
    Fermann, Martin E.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Optical Frequency Comb Fourier Transform Spectroscopy with Resolution beyond the Path Difference Limit2016Ingår i: Proceedings Conference on Lasers and Electro-Optics Part of CLEO: 2016 5–10 June 2016, San Jose, California, United States, 2016Konferensbidrag (Refereegranskat)
    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.

  • 21.
    Rutkowski, Lucile
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Valiev, Damir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Lodi, Lorenzo
    Yurchenko, Sergey
    Polyansky, Oleg L.
    Tennyson, Jonathan
    Schmidt, Florian M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Detection of OH and H2O in an Atmospheric Flame by Near-Infrared Optical Frequency Comb Spectroscopy2017Ingår i: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), IEEE, 2017Konferensbidrag (Refereegranskat)
    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.

  • 22.
    Rutkowski, Lucile
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Valiev, Damir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Tkacz, Arkadiusz
    Schmidt, Florian M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Detection of OH in an atmospheric flame at 1.5 μm using optical frequency comb spectroscopy2016Ingår i: Photonics Letters of Poland, ISSN 2080-2242, E-ISSN 2080-2242, Vol. 8, nr 4, s. 110-112Artikel i tidskrift (Refereegranskat)
    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.

  • 23.
    Rutkowski, Lucile
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zhao, Gang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. State Key Laboratory of Quantum Optics and Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China.
    Hausmaninger, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sensitive and broadband measurement of dispersion in a cavity using a Fourier transform spectrometer with kHz resolution2017Ingår i: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 25, nr 18, s. 21711-21718Artikel i tidskrift (Refereegranskat)
    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.

  • 24.
    Rutkowski, Lucile
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Valiev, Damir M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Lodi, Lorenzo
    Qu, Zhechao
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Ghorbani, Ramin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Polyansky, Oleg L.
    Jin, Yuwei
    Tennyson, Jonathan
    Schmidt, Florian M.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för tillämpad fysik och elektronik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Measurement of H2O and OH in a Flame by Optical Frequency Comb Spectroscopy2016Ingår i: Proceedings Conference on Lasers and Electro-Optics, 2016Konferensbidrag (Refereegranskat)
    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.

  • 25.
    Rutkowski, Lucile
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Masłowski, Piotr
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Khodabakhsh, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Optical frequency comb Fourier transform spectroscopy with sub-nominal resolution and precision beyond the Voigt profile2018Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 204, s. 63-73Artikel i tidskrift (Refereegranskat)
    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.

1 - 25 av 25
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