Free-running 91-µm distributed-feedback quantum cascade laser linewidth measurement by heterodyning with a C^18O_2 laser

Weidmann, Damien; Joly, Lilian; Parpillon, V.; Courtois, D.; Bonetti, Yargo; Aellen, Thierry; Beck, Mattias; Faist, Jérôme; Hofstetter, Daniel

doi:10.1364/ol.28.000704

Cited by 25 publications

(12 citation statements)

References 13 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: 83%

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: 83%

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

et al. 2004

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“…Even better performances have been recently obtained by using heterogeneous quantum cascade structures into an external cavity configuration [8]: single-mode tuning range of more than 100 cm -1 (10% the center wavelenght) has been achieved. On the side of spectral purity, upper limits to the emission linewidth of external cavity QCLs have been estimated in few MHz [9,10], and are the same order of magnitude of those measured for free-running DFB QCLs [11,12], also verified by our experiments [13]. This fact confirms that the external cavity does not significantly contribute to the narrowing of the emission linewidth.…”

Section: Introductionsupporting

confidence: 87%

Quantum cascade lasers as metrological tools for space optics

Bartalini

Borri

Galli³

et al. 2017

International Conference on Space Optics — ICSO 2008

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A distributed-feedback quantum-cascade laser working in the 4.3÷4.4 µm range has been frequency stabilized to the Lamb-dip center of a CO2 ro-vibrational transition by means of first-derivative locking to the saturated absorption signal, and its absolute frequency counted with a kHz-level precision and an overall uncertainty of 75 kHz. This has been made possible by an optical link between the QCL and a near-IR Optical Frequency Comb Synthesizer, thanks to a non-linear sum-frequency generation process with a fiber-amplified Nd:YAG laser. The implementation of a new spectroscopic technique, known as polarization spectroscopy, provides an improved signal for the locking loop, and will lead to a narrower laser emission and a drastic improvement in the frequency stability, that in principle is limited only by the stability of the optical frequency comb synthesizer (few parts in 10 13 ). These results confirm quantum cascade lasers as reliable sources not only for high-sensitivity, but also for highprecision measurements, ranking them as optimal laser sources for space applications.

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“…The use of the OFCS and the locking loop marks an important improvement over the existing literature. 12,13 Thanks to frequency stabilization of our device, in fact, acquisitions of the beat note over longer time intervals are possible. In particular, this allows a comparison (Fig.…”

Section: Preliminary Considerations On the Lasermentioning

confidence: 99%

Quantum cascade lasers for high-resolution spectroscopy

et al. 2010

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Abstract. Despite the growing interest that quantum cascade lasers (QCLs) are gaining, they still present a few unclear aspects of their fundamental properties, such as spectral purity, that need to be deeply investigated when aiming to make these innovative laser sources suitable for high-resolution spectroscopy and metrology. This paper is a review of our efforts towards QCL-based high-resolution spectroscopy and of our experimental investigation of QCLs ’ frequency noise, aimed to discover the ultimate performances attainable by QCLs and to develop the exper-imental techniques required to achieve them. Our results, confirmed by several independent measurements, show that QCLs have a very small intrinsic linewidth buried under a large frequency-noise background. The development of appropriate frequency stabilization techniques will make QCLs well suited for high-resolution spectroscopy and metrology in the mid and far IR. C © 2010 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3498775] Subject terms: quantum cascade lasers; high-resolution infrared molecular spec

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Free-running 91-µm distributed-feedback quantum cascade laser linewidth measurement by heterodyning with a C^18O_2 laser

Cited by 25 publications

References 13 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

Quantum cascade lasers as metrological tools for space optics

Quantum cascade lasers for high-resolution spectroscopy

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