Chirped laser dispersion spectroscopy for remote openpath tracegas sensing. Laser dispersion spectroscopy a unique approach to gas sensing about. Chirped laser dispersion spectroscopy clads is suitable for remote. Chirped laser dispersion spectroscopy using a directly.
The system is based on chirped laser dispersion spectroscopy clads, which probes the presence of methane molecules through optical dispersion using a multifrequency beam. Pdf chirped laser dispersion spectroscopy for remote open. Jul 19, 2012 laser spectroscopic techniques suitable for molecular dispersion sensing enable new applications and strategies in chemical detection. Chirped laser dispersion spectroscopy with harmonic detection of molecular spectra 479 fig. Osa molecular dispersion spectroscopy for chemical sensing. Molecular dispersion spectroscopy new capabilities in laser. Strictly allfiber picosecond ytterbium fiber laser utilizing. The following sections present the theoretical aspects of the method, the corresponding experimental studies and results, and a discussion on the merits of chirped laser dispersion spectroscopy clads. Instead of detecting changes in light intensity as in an absorptionbased measurement like all existing optical sensors, he. Laser based chemical sensors are of importance for a variety of applications in the environmental, industrial, security, and biomedical. In the following, special laser mirror designs exhibiting. This paper discusses the current stateofthe art and provides an overview of recently developed chirped laser dispersion spectroscopy clads based.
A normal requirement for dfts is that the pusles are linear chirped to prevent distortion of the measured data, but this. Other applications of chirped pulses include chirpassisted sum frequency generation casfg 19, dispersive fourier transform spectroscopy dfts 20 and telecommunications 21. Abstract the subject of this thesis is the fundamentals, implementation, and applications of chirped laser dispersion spectroscopy clads, an alternative dispersion spectroscopy technique that aims to overcome some limitations of absorptionbased sensing. Chirped laser dispersion spectroscopy with harmonic detection. Laser pulses centred on 810nm with 90nm fullwidth at halfmaximum bandwidth are chirped with a spatial light modulator in a. Dispersioncancelled imaging with chirped laser pulses. In clads a laser beam containing multiple waves of different frequencies is transmitted through a measured sample. Chirped pulse amplifiers are seeded with lowenergy ultrashort pulses temporally broadened in a dispersive pulse stretcher to permit for amplification without damaging the gain medium. Methane leak detection using chirped laser dispersion. Proofofprinciple experiments in the nearinfrared spectral range are presented and potential. Remote methane sensor for emissions using chirped laser dispersion spectroscopy the project objective is to develop, test, and field demonstrate a remote sensing methane detector for the use on aircraft and vehicles to detect leaks along midstream infrastructure of the natural gas supply chain. Chirped laser dispersion spectroscopy with harmonic detection of.
The subject of this thesis is the fundamentals, implementation, and applications of chirped laser dispersion spectroscopy clads, an alternative dispersion spectroscopy technique that aims to overcome some limitations of absorptionbased sensing. Common techniques depend on measuring detected intensity to derive concentration. Temporal characterization of chirped femtosecond laser pulses. Read remote midinfrared sensing using chirped laser dispersion spectroscopy, proceedings of spie on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. May, 2011 read remote midinfrared sensing using chirped laser dispersion spectroscopy, proceedings of spie on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Longrange openpath greenhouse gas monitoring using mid. Signaltonoise ratio in chirped laser dispersion spectroscopy. Thus, precise characterization of chirped laser pulses is important for the proper control and optimization of atomic or molecular processes in laser field.
Pdf chirped laser dispersion spectroscopy with differential. Ultrafast laser technology and spectroscopy 1 ultrafast laser technology and spectroscopy gavin d. Introduction to laser spectroscopy connecting repositories. Remote methane sensor for emissions from pipelines and. Longrange openpath greenhouse gas monitoring using midinfrared laser dispersion spectroscopy nart daghestani, richard brownsword, and damien weidmann space science and technology department, rutherford appleton laboratory, harwell oxford campus, didcot ox11 0qx, united kingdom damien. In this technique, a singlefrequency laser that is capable of being frequency chirped at high rates is used e. Molecular dispersion spectroscopy in a co2filled all. Cmclads inherits the full advantages of conventional clads and additionally overcomes. As the laser is frequency chirped, the difference in. Chirped lasers dispersion spectroscopy implemented with. This is the rst time that a dispersion cancelled technique has been used to image the interior structure of a biological sample. Chirped laser dispersion spectroscopy clads utilizing direct modulation of a quantum cascade laser qcl is presented. Electrons oscillating in the field of such intense light become relativistic.
Technology note laser dispersion spectroscopy a unique approach to gas sensing about. These special laser mirrors, which are potentially free from all the drawbacks listed above, can be used for broadband feedback, intracavity and extracavity dispersion control. Abstract chirped laser dispersion spectroscopy clads has been introduced recently as a technique that performs molecular detection based. Chirped laser dispersion spectroscopy for remote sensing. In particular the model shows that the snr is optimal for a given value of the laser chirp rate. Chirped laser dispersion spectroscopy with parametric. Teraxions allfiber powerspectrum dmr chirped fiber bragg gratings fbg provide precise compensation for either anomalous or normal dispersion for modelocked ultrafast lasers. We present a realtime chirped laser dispersion spectrometer. Chirped laser dispersion spectrometers clads developed for the monitoring of atmospheric methane and carbon dioxide will be presented. To the best of our knowledge this is the first demonstration of openpath laser based tracegas detection using a molecular dispersion measurement. Manipulating impulsive stimulated raman spectroscopy with a. Pdf chirped laser dispersion spectroscopy for remote. This paper discusses the current stateofthe art and provides an overview of recently developed chirped laser dispersion spectroscopy clads based techniques.
Remote methane sensor for emissions using chirpedlaser dispersion spectroscopy the project objective is to develop, test, and field demonstrate a remote sensing methane detector for the use on aircraft and vehicles to detect leaks along midstream infrastructure of the natural gas supply chain. It consists of a singlefrequency laser source typically a dfb laser diode, and a machzehnder interferometer with an acoustooptical modulatorfrequency. Chirped laser dispersion spectroscopy for remote sensing of methane at 1. Selected methods of timeresolved laser spectroscopy 175 8.
Capability of direct singlesideband modulation is a unique feature of qcls that exhibit a low. Allfiber midinfrared difference frequency generation source. Chirped laser dispersion spectroscopy for laserbased. By interfacing with a common laser source, a single apparatus forms a system by which one would duplicate many of the capabilities of several different national laboratoryscale facilities. The stretching and compression uses devices that ensure that the different color components of the pulse travel different distances. Michal nikodem, chirped laser dispersion spectroscopy with parametric downconversion for openpath gas sensing, opt. The dispersion sensing is based on measurement of instantaneous frequency of an optical heterodyne beatnote which provides high immunity to optical power fluctuations.
At its core, chirped pulse amplification cpa works by diluting the light, so that it can be amplified to a larger total power without reaching a dangerous intensity, but it does this stretching in time, i. Their impact on the signaltonoise ratio snr achievable with the clads sensing method is analyzed through a noise model supported by experimental results. Chirped laser dispersion spectroscopy for laserbased hydrogen sulfide detection in openpath conditions. Laser spectroscopic techniques suitable for molecular dispersion sensing enable new applications and strategies in chemical detection. Clads is based on measurement of optical dispersion associated with a resonant molecular transition. Lowfrequency coherent raman spectroscopy using spectral.
By controlling the laser bias nearly single and dualsideband clads operation can be realized in an extremely simplified optical setup with no external optical modulators. Recently we have introduced chirped laser dispersion spectroscopy clads, technique that is particularly wellsuited for remote openpath gas sensing 1. To the best of our knowledge this is the first demonstration of openpath laserbased tracegas detection using a molecular dispersion measurement. The key innovation is heterodyne enhanced chirp modulated chirped laser absorption spectroscopy he. Laser spectroscopy is a powerful tool for quantitative chemical detection. Remote midinfrared sensing using chirped laser dispersion. Until, that is, chirped pulse amplification came around to solve the problem. Halina abramczyk, in introduction to laser spectroscopy, 2005. Nov 30, 2010 by interfacing with a common laser source, a single apparatus forms a system by which one would duplicate many of the capabilities of several different national laboratoryscale facilities. Chirped pulse amplification cpa is a technique for amplifying an ultrashort laser pulse up to the petawatt level, with the laser pulse being stretched out temporally and spectrally, then amplified, and then compressed again.
Quantitative studies and experimental validation of noise sources occurring in chirped laser dispersion spectroscopy clads are reported. Molecular dispersion spectroscopy new capabilities in. An apparatus and method for detecting refractive index variations in a sample is disclosed. A proof of concept heterodyneenhanced chirped laser dispersion spectroscopy system is presented. The dmr has especially high dispersion accuracy and is compatible with most modelocked laser configurations for a range of customizable wavelengths and cavity. Frequencymultiplexed gas sensing using chirped laser. Chirped laser dispersion spectroscopy in dual sideband. This paper discusses the current state of the art and provides an overview of recently developed chirped laser dispersion spectroscopy cladsbased techniques. A widely tunable, fully monolithic, midinfrared difference frequency generation source and its application in the dispersionspectroscopybased laser trace gas detection of methane and ethane, near 2938 and 2998 cm. In the rst experiment a chirped pulse interferometer is used to image the cells of an onion. Chirped laser dispersion spectroscopy dispersion laser spectroscopy. In this paper we present a prototype instrument for remote openpath detection of nitrous oxide. Remarkable progress in development of high power femtosecond pulses and their applications has been achieved since introduction of chirped pulse amplification cpa in mid 1980s. Molecular dispersion spectroscopy for chemical sensing.
Us20120268746a1 chirp modulationbased detection of chirped. Two optical arrangements based on electrooptical modulators significantly reduce clads system complexity and enable optimum performance when applied to detection of ghzwide molecular transitions. Peak laser power and focused intensity has increased several orders of magnitude. Using quantum cascade laser as the source, a minimalistic and compact system operating at 7. Chirped laser dispersion spectroscopy clads uses a twocolor dynamic interferometric heterodyne detection to measure optical dispersion caused by molecular transitions. A basic setup for chirped laser spectroscopy as demonstrated by wysocki and weidman is presented in fig.
Reid university of leeds, leeds, uk klaas wynne university of strathclyde, glasgow, uk 1 introduction 1 2 ultrafast lasers and ampli. The apparatus includes a multi frequency laser source configured to generate a mixed laser beam having at least two optical frequencies. In this paper, a new detection scheme based on chirp modulation cm and subsequent phasesensitive detection is described. Characterization of an actively linearized ultrabroadband. Infrared using quantum cascade lasers was chirped laser dispersion spectroscopy clads. Pdf a feasibility study of openpath methane detection at 3. Lds laser dispersion spectroscopy, is a new gas sensing technique that applies a novel approach tunable diode laser spectroscopy.
Chirped laser dispersion spectroscopy for remote open. Lowfrequency coherent raman spectroscopy using spectralfocusi ng of chirped laser pulses 155 p1 d e 0. This paper provides an analysis of direct modulation of a quantum cascade laser for applications in chirped laser dispersion spectroscopy clads. We present a detailed theoretical and experimental characterization of a new methodology for stimulated raman spectroscopy using two duplicates of a chirped, broadband laser. The spectroscopic information can be extracted by frequency demodulating the beatnote signal through optical heterodyne detection at the photodetector. The chirpmodulated mixed laser beam being configured to pass through the sample. In remote sensing systems, where low return powers are expected, the addition of an optical local oscillator and subsequent nonlinear processing allows for improved performance. May 26, 2011 chirped laser dispersion spectroscopy clads uses a twocolor dynamic interferometric heterodyne detection to measure optical dispersion caused by molecular transitions. Remote methane sensing system based on heterodyne enhanced. A spectroscopic method of molecular detection based on dispersion measurements using a frequencychirped laser source is presented. Characterization of an actively linearized ultrabroadband chirped laser with a fiber laser optical frequency comb zeb w. Chirped laser dispersion spectroscopy clads has been introduced recently as a technique that performs molecular detection based on measurement of optical dispersion. New configuration for nearinfrared chirped laser dispersion spectroscopy clads is presented.
Chirped laser dispersion spectroscopy for remote openpath. One can see that it consists of the regenerative amplifier described in section 6. Chirped pulse amplification center for ultrafast optical. Invitedpaper theoryanddesignofchirpeddielectriclasermirrors. Strictly allfiber picosecond ytterbium fiber laser. Clads, an approach that uses optical dispersion rather than absorption to detect atmospheric ch 4. Stimulated raman spectroscopy using chirped pulses. Pdf chirped laser dispersion spectroscopy with directly. Dispersion spectroscopy in the midir using quantum cascade. Osa chirped lasers dispersion spectroscopy implemented with. Us20120268746a1 chirp modulationbased detection of. Cmclads inherits the full advantages of conventional clads and additionally overcomes some of its. A sinusoidal function generator is configured to modulate the optical frequencies to generate a chirpmodulated mixed laser beam.
A spectroscopic method of molecular detection based on dispersion measurements using a frequency chirped laser source is presented. Optical heterodyneenhanced chirped laser dispersion. Dispersion spectroscopy in the midir using quantum. We report new approaches for signal generation in chirped laser dispersion spectroscopy clads. An infrared quantum cascade laser emitting around 1912 cm.
May 26, 2012 chirped laser dispersion spectroscopy clads has been introduced recently as a technique that performs molecular detection based on measurement of optical dispersion. Clads detects the phase shift of laser light resulting from. Intense chirped femtosecond pulses can be produced in a chirped pulse amplification cpa laser which is widely adopted as a standard laser configuration for ultrashort highpower lasers. The sample under study is a mixture of nitric oxide in dry nitrogen.
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