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NASA's ER-2 high-altitude aircraft takes off from Dryden Flight Research Center NASA photo courtesy of Tony Landis. The ALIAS is located in the superpod on the right wing. This payload carries numerous other NASA, National Oceanic and Atmospheric Administration, and university experiments.
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A tunable quantum-cascade (QC) laser has been flown on NASA's ER-2 high-altitude aircraft to produce the first atmospheric gas measurements with this newly invented device, an important milestone in the QC laser's future planetary, industrial, and commercial applications. Using a cryogenically cooled QC laser during a series of 20 aircraft flights...
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... flights from Kiruna, Sweden, in spring 2000 as part of NASA's Stratospheric Aerosol and Gas Experiment SAGE III Ozone Loss and Validation Experiment SOLVE mission, JPL's aircraft laser infrared absorption spec- trometer ALIAS 17 was taken to Edwards Air Force Base in September 1999 for test flights on NASA's ER-2 aircraft. The ER-2 aircraft see Fig. 2 is a single-engine, high-altitude aircraft that is a modi- fied U2 aircraft, capable of flying to altitudes greater than 20 km. On 23, 25, and 28 September 1999, NASA pilots Ken Broda, Jan Nystrom, and Jim Bar- rilleaux each flew a single flight from the NASA Dry- den Flight Research Center at Edwards Air Force Base on 2-8 h sorties ...
Citations
... The rapid development of QCLs contributed to their widespread use for spectroscopic applications in the mid-IR and THz spectral range, targeting atmosphere constituents' studies, the measurement of planetary gases composition, astronomy, astrophysics, astrochemistry and spaceborne instrumentation [1][2][3][4][5][6][7][8][9][10][11][12]. The competing sources for this range are superlattice multipliers, which have a far lower output power but can cover the 0.1-to-1 THz range [13][14][15][16][17], which has a strong potential for medical diagnostics [18]. ...
This paper reports the results obtained for a distributed-feedback quantum cascade laser (DFB-QCL) exposed to different fluences of proton particles: 1014, 1015 and 1016 p/cm2. Dedicated laboratory setups were developed to assess the irradiation-induced changes in this device. Multiple parameters defining the QCL performances were investigated prior to and following each irradiation step: (i) voltage-driving current; (ii) emitted optical power-driving current; (iii) central emitting wavelength-driving current; (iv) emitted spectrum-driving current; (v) transversal mode structure-driving current, maintaining the system operating temperature at 20 °C. The QCL system presented, before irradiation, two emission peaks: a central emission peak and a side peak. After proton irradiation, the QCL presented a spectral shift, and the ratio between the two peaks also changed. Even though, after irradiation, the tunning spectral range was reduced, at the end of the tests, the system was still functional.
... These experimental works primarily employed N2O IR emission diagnostics near 4.5 μm in the ν3 (asymmetric stretch) band of N2O to monitor N2O time histories behind reflected (and/or incident) shock waves. However, while works have been performed using N2O IR absorption near 2.0 μm [8] and 8.0 μm [9], these IR absorption diagnostics were employed only at near-ambient temperatures. Absent from the literature is the usage of N2O IR absorption as a high-temperature, shock-tube diagnostic for N2O. ...
... I N RECENT years, quantum cascade lasers (QCLs) have undergone a rapid development and been demonstrated as the most promising coherent laser source in many applications such as high-resolution spectroscopy, free-space communication and environment monitoring [1]- [3]. By using distributed feedback (DFB) grating structures, QCLs with narrow linewidth and fast wavelength tunability can be obtained, which are very essential in gas-sensing systems [4]- [6]. ...
In this work, quantum cascade lasers (QCLs) based on excited-states injection are presented. The operating voltage is significantly reduced compared to the conventional ground-state injection design. Devices emitting at ~5.25 μm were fabricated through standard buried-heterostructure (BH) processing. Stable single-mode emission was observed by implementing a buried first-order distributed feedback (DFB) grating. The maximum output power of the DFB QCL with 2-mm cavity length was more than 300 mW at 10 °C with a high wall-plug efficiency (WPE) of 5.6% in continuous-wave (CW) mode.
... The most significant system aspect is whether the spectral selectivity is implemented in the light source or in the detector. Scanning the spectrum with a tunable light source -either in narrowband with tunable diode-lasers [14] or in wideband using quantum cascade lasers [15]-and selecting one specific wavelength, as is the case in the nondispersive IR (NDIR) gas sensor [16], are two main methods used for implementing spectral selectivity in the light source. The second option is implemented in the detector, where the spectrum is scanned using a wideband source and a tunable narrowband filter at the detector [17]. ...
A miniaturized methane (CH4) sensor based on nondispersive infrared absorption is realized in MEMS technology. A high level of functional integration is achieved by using the resonance cavity of a linear variable optical filter (LVOF) also as a gas absorption cell. For effective detection of methane at λ = 3.39 µm, an absorption path length of at least 5 mm is required. Miniaturization therefore necessitates the use of highly reflective mirrors and operation at the 15th-order mode with a resonator cavity length of 25.4 µm. The conventional description of the LVOF in terms of the Fabry-Perot resonator is inadequate for analyzing the optical performance at such demanding boundary conditions. We demonstrate that an approach employing the Fizeau resonator is more appropriate. Furthermore, the design and fabrication in a CMOS-compatible microfabrication technology are described and operation as a methane sensor is demonstrated.
... Many small molecules have their strongest absorption lines in the spectral region between ~3 and 10 μm, the spectral region spanned by QCL's and ICL's. Trace gas instruments utilizing these mid-IR lasers are being designed at universities [9][10][11][12][13][14][15][16][17], government laboratories [18][19][20] and in corporations [21][22][23][24][25][26][27][28][29], in order to help answer pressing questions in atmospheric and environmental research. QCL's and ICL's are nearly ideal sources for trace gas instruments that must operate outside the laboratory, since they can operate at near room temperature, they are small and robust, and can be easily modulated in wavelength. ...
... The set of lines for CO 2 at 2310 cm −1 are exceptional in these regards [15,20,26]. Water is a more difficult case, because of the much lower natural abundance of deuterated water (fraction HDO/H 2 O ~3x10 −4 ), especially compared to the 18 ...
A design and results for an instrument with a quantum cascade laser and an antimonide diode laser to measure simultaneously and with high precision seven isotopologues of carbon dioxide and water vapor. Methods and results for determining the effects that limit absorption noise at the level of 5x10⁻⁶ are presented and discussed.
... To the best of the authors' knowledge, Webster et al. (141) demonstrated a QCLbased instrument for the first time on the National Aeronautics and Space Administration's (NASA) ER-2 high-altitude aircraft for atmospheric gas measurements, which is an important milestone in the QCL's future planetary, industrial, and commercial applications. Using a cryogenically cooled CW-QC laser during a series of 20 aircraft flights beginning in September 1999 and extending through March 2000, they took measurements of CH 4 and N 2 O gas up to ∼20 km in the stratosphere over North America, Scandinavia, and Russia. ...
Infrared laser absorption spectroscopy (LAS) is a promising modern technique for sensing trace gases with high sensitivity, selectivity, and high time resolution. Mid-infrared quantum cascade lasers, operating in a pulsed or continuous wave mode, have potential as spectroscopic sources
because of their narrow linewidths, single mode operation, tunability, high output power, reliability, low power consumption, and compactness. This paper reviews some important developments in modern laser absorption spectroscopy based on the use of quantum cascade laser (QCL) sources. Among
the various laser spectroscopic methods, this review is focused on selected absorption spectroscopy applications of QCLs, with particular emphasis on molecular spectroscopy, industrial process control, combustion diagnostics, and medical breath analysis.
... From a practical point of view, TDLAS measurements often use zero-air background subtraction to improve instrument performance, especially in harsh environments, such as airborne measurements (127)(128)(129)(130)(131). Zero-air background subtraction can very effectively remove low-frequency optical fringing noise, which is frequently a major source of sensitivity-limiting noise. ...
Tunable diode laser absorption spectroscopy (TDLAS), as a noninvasive spectroscopic method, permits high-resolution, high-sensitivity, fast, in situ absorption measurements of atomic and molecular species and narrow spectral features in gaseous, solid, and liquid phases. Advances in new diode laser sources and laser spectroscopic techniques generally have triggered an increasing application of TDLAS in various disciplines (for example, atmospheric environmental monitoring, chemical analysis, industrial process control, medical diagnostics and combustion monitoring, etc.) over the last four decades. This article reviews some important developments in TDLAS, from its basic principles as a spectroscopic tool to the demonstration of gas absorption measurements, emphasizing signal enhancement and noise reduction techniques developed for improving current TDLAS performance.
... A lock-in amplifier is used to detect signals at the modulating frequency or at its higher harmonics. The demodulated envelop of the amplitude of each of the harmonic signal is dependent on the absorption of the gas and hence information regarding various gas parameters can be derived from it [5][6][7][8]. Although the combined effect of IM and FM was known for a long time [9,10], it was not included in the theoretical model of WMS given by Arndt [11], Reid and Labrie [12] and Supplee, Whittaker, and Lenth [13]. ...
This paper reports time-varying and simultaneous detection of the pressure and concentration, of hazardous gases such as methane, carbon dioxide and ammonia using tunable diode laser spectroscopy (TDLS). The concentration and pressure of the gases is extracted with a time resolution of 10s, which makes this method useful in applications that require in situ, real-time measurements of several gases. A calibration-free wavelength modulation spectroscopy (WMS) approach known as the Residual Amplitude Modulation (RAM) method has been used at a modulation frequency when intensity modulation (IM) is at phase-quadrature to the frequency modulation (FM). TDLS offers the dual advantage of remote detection of gases and quantification of gas parameters. This makes them ideally suited to hazardous environments such as coal mines.
... To the best of the authors' knowledge, Webster et al. (141) demonstrated a QCLbased instrument for the first time on the National Aeronautics and Space Administration's (NASA) ER-2 high-altitude aircraft for atmospheric gas measurements, which is an important milestone in the QCL's future planetary, industrial, and commercial applications. Using a cryogenically cooled CW-QC laser during a series of 20 aircraft flights beginning in September 1999 and extending through March 2000, they took measurements of CH 4 and N 2 O gas up to ∼20 km in the stratosphere over North America, Scandinavia, and Russia. ...
Abstract Since the first demonstration in 1994, progress in the development of quantum cascade lasers (QCLs) has been breathtakingly rapid. Various techniques based upon novel QCLs have attracted much interest from researchers working in science and engineering disciplines (atmospheric environmental monitoring, chemical analysis, industrial process control, medical diagnostics, applications of life science, etc.) over the course of approximately the last two decades. Some background and recent advances in the development of QCLs are discussed together with a brief outline of a few representative atmospheric chemical species and their spectral features, as well as a short summary of terahertz-QCL. Among the various laser spectroscopic methods, the focus in this review is directed toward selected applications of QCL absorption spectroscopic techniques, which are commonly used to measure atmospheric trace gases, with particular emphasis on ground-based eddy covariance measurements, isotope measurements, and airborne-platform atmospheric measurements.
... Most N 2 O analysers are currently equipped with pulsed DFB-RT-QCLs, and based-on traditional TDLS (tunable diode laser spectroscopy, typical detection limit of absorbance ∼10 −3 ). In order to overcome the inherent drawbacks (lower sensitivity and laser pulsed fluctuation) in pulsed laser based-TDLS, a long-path absorption cell (typical 76 m or more) and background subtraction procedure have to be used, for example, the QCL spectrometer [11] used for monitoring the concentrations of CH 4 and N 2 O in the troposphere by Duxbury group at University of Strathclyde (UK), the ALIAS spectrometer [12] that has also been used to make stratospheric measurements of CH 4 and N 2 O by Webster and his group, the model QCL-TILDAS-76 [13,14] developed by Aerodyne Research Inc. (ARI, USA) and the Harvard-QCLS developed with their collaborators [15]. Some instruments in ARI have been recently modified to employ CW-DFB-RT-QCLs [16], which have some significant advantages over pulsed QCLs [17]. ...
