Remote Chemical Sensing Using Quantum Cascade Lasers

Harper, Warren W.; Strasburg, Jana D.; Aker, Pam M.; Schultz, John F.

doi:10.2172/15010485

Cited by 3 publications

(3 citation statements)

References 2 publications

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“…As an example, the photosignal temporal run of the 8.2 µm lidar recorded from the 2.25 km distant retroreflector is shown in Fig. 3 [14]. The autocorrelation timescales of shown signals are 68 and 25 ms for the morning and day records, respectively.…”

Section: Atmospheric Turbulence Effect and Detection Of Variable Plumesmentioning

confidence: 99%

“…With the origin of the sufficiently powerful quantum cascade lasers (QCL) they entered the field of remote sensing. Lidars with QCL transmitters showed the detection limit of about ∼1 ppm m for ozone [13] and H 2 S [14]. Despite the compactness the deficiency of QCLs is the narrow tuning range.…”

Section: Equipment and Meteorological Aspects Of Remote Sensing With mentioning

confidence: 99%

“…Obviously the signal in the morning is less noisy than that one hour after midday. The indicator of signal irregularity, the scintillation index σ 2 i , was 0.00872 at 6:30 AM and 0.495 at 1:05 PM, that is, an increase by more than a factor of fifty was observed [14]. When working with the beam path of some kilometres and choosing propitious hours, the daily variation of turbulence has to be taken into account.…”

Section: Atmospheric Turbulence Effect and Detection Of Variable Plumesmentioning

confidence: 99%

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Application of atmosphere sensing by infrared lidars for environmental protection and industry needs

Švedas¹,

Vaicikauskas²,

Kaucikas³

2010

Lithuanian J. Phys.

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The paper analyses some equipment and methodological aspects of atmospheric pollution monitoring by infrared lidars. Features of optical parametric oscillators (including our created two-stage system) operating in the spectral ranges of molecular fundamental vibrations are discussed. The environment protection and industry demands for this remote monitoring technology are considered. Despite the progress in the technology and low detection limits achieved, the reliable and fast identification of pollutants is far from perfection. Inner and outer factors worsening the lidar performance, i. e. stability of the transmitted pulse energy, atmospheric turbulence, and irregularity of the pollutant plume near the source, are examined. A lidaric measurement model implying pulse stability was developed and applied to the 8-14 µm and 0.5 mJ per pulse lidar operating in the topographic target mode with the 0.05 m 2 telescope and the mercury cadmium telluride detector. It has been found that the laser pulse energy instability (energy dispersion parameter D) essentially worsens the detection limit in shorter ranges (<2 km for D =1%). Adaptation of lidar technology to the fast varying irregular plumes was tested experimentally. Plume detection events were processed using the probabilistic model, and the probability of false alarm was evaluated.

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Section: Atmospheric Turbulence Effect and Detection Of Variable Plumesmentioning

confidence: 99%

Section: Equipment and Meteorological Aspects Of Remote Sensing With mentioning

confidence: 99%

Section: Atmospheric Turbulence Effect and Detection Of Variable Plumesmentioning

confidence: 99%

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Application of atmosphere sensing by infrared lidars for environmental protection and industry needs

Švedas¹,

Vaicikauskas²,

Kaucikas³

2010

Lithuanian J. Phys.

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Utilizing broad gain bandwidth in quantum cascade devices

et al. 2010

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The utilization of the broad gain bandwidth available from quantum cascade (QC) devices is considered. The performance of homogeneous and heterogeneous QC gain media is explored in an externalcavity configuration. Paradigms for realizing fixed wavelength or broad tuning performance of QC devices are considered. C 2010 Society of PhotoOptical Instrumentation Engineers. IntroductionQuantum cascade (QC) devices have become the standard gain media for lasers where high power, room-temperature operation, and continuous wavelength coverage are required in the midinfrared region of 3 to 12 μm. Recently, a tuning range of 432 cm -1 was demonstrated 1 for a QC device run in external-cavity mode. Such a broad gain bandwidth is comparable to results achieved with other semiconductor gain media: For example, 596 cm -1 of tuning has been demonstrated in near-IR diodes, 2 and 444 cm -1 in cryogenically cooled mid-IR Pb-salt diodes. 3 Utilizing the broad gain bandwidth of QC devices is an important consideration in the commercialization of QC-based lasers.Broad gain bandwidth in a gain medium offers potential advantages in the manufacture of lasers. For fixedwavelength lasers, a larger offering of wavelengths can be made without having to create multiple gain media. 4 Broad gain bandwidth can be converted into tuning range to access wider spectral ranges. 5 In both cases, however, a method is needed to restrict the laser operation to a single mode or subset of modes that are useful for the application of interest.Distributed feedback (DFB) structures have been integrated into the QC waveguide to restrict lasing to a narrow wavelength range. 6 This approach has the advantage that an extremely compact single-mode laser can be made with narrow linewidth and low frequency noise. 7 DFB lasers can be used in an intrapulse mode to perform spectroscopy of rotationally resolved gas molecules over a few inverse centimeters. 8 Ultimately, however, DFB QC lasers can only realize broader tuning by changing temperature, which limits their effective tuning range to less than 20 cm -1 , not nearly enough to utilize the full gain bandwidth available in QC devices. Moreover, from a manufacturing standpoint, different DFB QC devices have to be stocked for each fixed wavelength, negating the advantage of broad gain bandwidth in manufacturing.An alternative method, which allows for manufacturing settability of wavelength and broad tuning if required, is an external-cavity configuration. External-cavity QC lasers have been successfully employed to realize both narrow linewidth and broad tuning. 9, 10 A typical external cavity arrangement with grating feedback in Littrow configuration is shown in

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