High-resolution (Doppler-limited) spectroscopy using quantum-cascade distributed-feedback lasers

Sharpe, Steven W.; Kelly, James Floyd; Hartman, John S.; Gmachl, Claire F.; Capasso, Federico; Sivco, Deborah L.; Baillargeon, J. N.; Cho, A. Y.

doi:10.1364/ol.23.001396

Cited by 100 publications

(39 citation statements)

References 11 publications

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“…This QCL line-width value is close to the one observed in the pure cw mode at cryogenic temperatures by Sharpe et al [14] (∼ 40 MHz) but still high compared to the ∼ 1 MHz achievable by reducing the current-source noise [15]. However, such a QCL line width is at least five times below the one observed in pulsed mode operation and insignificant if performing gas-concentration measurements at reduced pressures of ∼ 100 Torr (133.3 mbar).…”

Section: 3supporting

confidence: 88%

Mid-infrared trace-gas sensing with a quasi- continuous-wave Peltier-cooled distributed feedback quantum cascade laser

et al. 2004

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A recently developed distributed feedback quantum cascade laser (QCL) capable of thermoelectric-cooled (TEC) continuous-wave (cw) operation and emitting at ∼ 9 µm is used to perform laser chemical sensing by tunable infrared spectroscopy. A quasi-continuous-wave mode of operation relying on long current pulses (∼ 5 Hz, ∼ 50% duty cycle) is utilized rather than pure cw operation in order to extend the continuous frequency tuning range of the quantum cascade laser. Sulfur dioxide and ammonia were selected as convenient target molecules to evaluate the performance of the cw TEC QCL based sensor. Direct absorption spectroscopy and wavelengthmodulation spectroscopy were performed to demonstrate chemical sensing applications with this novel type of quantum cascade laser. For ammonia detection, a 18-ppm noise-equivalent sensitivity (1 σ) was achieved for a 1-m absorption path length and a 25-ms data-acquisition time using direct absorption spectroscopy. The use of second-harmonic-detection wavelengthmodulation spectroscopy instead of direct absorption increased the sensitivity by a factor of three, achieving a normalized noiseequivalent sensitivity of 82 ppb Hz −1/2 for a 1-m absorption path length, which corresponds to 2 × 10 −7 cm −1 Hz −1/2 . PACS 42.55.Px; 42.62.Fi; 07.88.+y IntroductionTunable laser spectroscopy has proved to be a technique well suited for achieving gas-phase concentration measurements from the ppm level to the low ppb range. Compact laser sources that emit in the mid infrared, where most molecules exhibit fundamental and therefore strong absorption ro-vibrational bands, are particularly useful. Among the available tunable laser sources, distributed feedback (DFB) quantum cascade lasers (QCLs) offer several unique advantages for the design of compact field-deployable optical sensors, such as high output power, narrow laser line width, compactness, robustness, single-mode operation, and . Until now, due to the relatively short upper-state lifetime of the involved intersubband transitions occurring in QCLs, their high operating voltage of nearly 10 V, and the associated large heat dissipation within the active zone, single-frequency operation has been achieved only in a pulsed mode at room temperature. Pulsed QCL operation suffers from three drawbacks: (1) due to thermal chirping, even a ∼ 10-ns pulse generates typical QCL line widths of ∼ 200-300 MHz, which is substantially larger than the Fourier-transform limit; (2) the main sensitivity limitation of a pulsed DFB QCL based spectrometer arises from the pulse to pulse intensity fluctuations that require the use of an additional reference beam for normalization [3,4]; and (3) the generation of nanosecond current pulses requires high-speed driving electronics and detectors as well as fast data acquisition. To overcome these drawbacks, considerable effort has been made towards achieving a DFB QCL that is able to operate in a continuouswave (cw) mode at room temperature.A first device, employing high-reflection-coated facets and operating up t...

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Section: 3supporting

confidence: 88%

Mid-infrared trace-gas sensing with a quasi- continuous-wave Peltier-cooled distributed feedback quantum cascade laser

et al. 2004

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“…This area is important not only because the characteristic absorption bands of, among others, CO, N 2 O, HCl and CH 2 O, lie herein, but also because there is an atmospheric transparent window in this range. Soon after the first appearance of these lasers, gas monitoring applications using various detection schemes were reported (Sharpe et al, 1998;Kosterev et al, 2008). Quantum-cascade lasers were used to detect ammonia and water vapor at 8.5 µm (Paldus et al, 1999), NO at 5.2 µm (Menzel et al, 2001), 12 CH 4 , 13 CH 4 and N 2 O isotopomers at 8.1 µm (Gagliardi et al, 2002), trace gases (CH 4 , N 2 O, H 2 O) in laboratory air at 7.9 µm (Kosterev & Tittel, 2002), carbon dioxide, methanol and ammonia at 10.1/10.3 µm (Hofstetter et al, 2001), CH 4 and NO at 7.9 µm and 5.3 µm (Grossel et al, 2006;Grossel et al, 2007) and simultaneously CO and SO 2 at 4.56 µm and 7.38 µm (Liu et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

CO2 Laser Photoacoustic Spectroscopy: I. Principles

Dumitraş¹,

Bratu²,

Popa³

2012

CO2 Laser - Optimisation and Application

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“…In the following years the Bell Labs group made a strong effort to improve the performance and illustrate the potential of these devices as a revolutionary light source for molecular spectroscopy [12,13]. Many important milestones for semiconductor lasers with emission wavelength in the mid infrared (3-15 µm), such as room temperature operation and high cw output power (∼1 W) at cryogenic temperatures, were demonstrated for the first time using QC lasers [5,6,11].…”

Section: The Fundamentals Of Quantum Cascade Lasersmentioning

confidence: 99%

GaAs Quantum Cascade Lasers: Fundamentals and Performance

Sirtori

2002

Les Lasers : Applications Aux Technologies De l'Information Et Au Traitement Des Matériaux

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Abstract. Quantum engineering of the electronic energy levels and tailoring of the wavefunctions in GaAs/Al x Ga 1−x As heterostructures allows to obtain the correct matrix elements and scattering rates which enable laser action between subbands. This article reviews the state-of-the-art of GaAs based quantum cascade lasers. These new light sources operate, with peak power in excess of 1 W at 77 K, in the 8-13 µm wavelength region, greatly extending the wavelength range of GaAs optoelectronic technology. Waveguides are based on an Al-free design with an appropriate doping profile which allows optical confinement, low losses and optimal heat dissipation. Finally, new active region designs aiming to improve the laser temperature dependence are discussed. Recent results on these devices confirm that the ratio between the conduction band discontinuity and the photon energy (∆E c /E laser ) is the dominant parameter controlling their thermal characteristic. The maximum operating temperature of these devices is 280 K for lasers with emission wavelength at ∼11 µm.

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High-resolution (Doppler-limited) spectroscopy using quantum-cascade distributed-feedback lasers

Cited by 100 publications

References 11 publications

Mid-infrared trace-gas sensing with a quasi- continuous-wave Peltier-cooled distributed feedback quantum cascade laser

Mid-infrared trace-gas sensing with a quasi- continuous-wave Peltier-cooled distributed feedback quantum cascade laser

CO2 Laser Photoacoustic Spectroscopy: I. Principles

GaAs Quantum Cascade Lasers: Fundamentals and Performance

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