Tunable Diode Laser Absorption Spectroscopy for Trace Gas Measurements with High Sensitivity and Low Drift PDF Download
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Author: Christoph Dyroff
Publisher:
ISBN: 9783866443280
Category : Technology (General)
Languages : en
Pages : 0
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Book Description
This book discusses the mechanical and opto-electronic design of laser spectrometers for measuring two very important atmospheric gases, namely water vapor and its isotopic ratios, and formaldehyde. For measuring water vapor, shot-noise limited sensitivity has been achieved by a careful choice of system components and data processing. For measuring formaldehyde, a selective sample modulation exploiting the Stark effect has been used to greatly improve the sensitivity.
Author: Christoph Dyroff
Publisher:
ISBN: 9783866443280
Category : Technology (General)
Languages : en
Pages : 0
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Book Description
This book discusses the mechanical and opto-electronic design of laser spectrometers for measuring two very important atmospheric gases, namely water vapor and its isotopic ratios, and formaldehyde. For measuring water vapor, shot-noise limited sensitivity has been achieved by a careful choice of system components and data processing. For measuring formaldehyde, a selective sample modulation exploiting the Stark effect has been used to greatly improve the sensitivity.
Author: A. Fried
Publisher:
ISBN:
Category : Air quality
Languages : en
Pages : 11
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Book Description
There has been an ongoing quest for development of ever more sensitive and selective detection methods for studying various gas molecules of atmospheric importance. Both laboratory and ambient studies often require instrumentation capable of measuring ultratrace concentrations of such gases at, and below, the parts-per-billion range. Concurrently, accurate calibration standards, particularly those verified by independent techniques, are also required. The sensitive, selective, and versatile technique of infrared tunable diode laser absorption spectrometry is especially well suited for ultra-trace gas measurements and calibration standards verification. This combination, which is not shared by many other measurement techniques, results from the fact that diode laser spectrometers can be operated in an absolute mode as well as a more sensitive relative mode. In this paper, we discuss these capabilities and present specific examples for the measurement and calibration of ultra-trace levels of the important atmospheric gases nitrogen dioxide (NO2) and hydrochloric acid (HCl). In addition, we further discuss the application of tunable diode laser absorption spectrometry in the verification of NO2 permeation standards using the gas-phase titration reaction between nitric oxide (NO) and ozone (O3).
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Tunable diode laser absorption spectroscopy (TDLAS) is an optical gas sensing technique in which the emission frequency of a laser diode is tuned over a gas absorption line of interest. A fraction of the radiation is absorbed by the sample gas and this can be determined from measurements of initial intensity and the intensity transmitted through the sample. The amount of light absorbed is related to the gas concentration. Additional modulation techniques combined with phase sensitive detection allow detection of very low gas concentrations (several parts per million). The advantages of using TDLAS for trace gas sensing include; fast response times, high sensitivity and high target gas selectivity. However, the sensitivity of many practical TDLAS systems is limited by the formation of unintentional Fabry-Perot interference fringes in the optical path between the source and detector. The spacing between the maxima of these fringes, in particular those generated in gas cells, can be in the same wavelength range as Doppler and pressure-broadened molecular line widths. This can lead to (1) interference fringe signals being mistaken for gas absorption lines leading to false concentration measurements or (2) distortion or complete obscuring of the shape and strength of the absorption line, such that the sensitivity of the instrument is ultimately limited by the fringes. The interference fringe signals are sensitive to thermal and mechanical instabilities and therefore can not be removed by simple subtraction techniques. Methods that have been proposed by previous workers to reduce the effects of interference fringes include careful alignment of optical components and/or mechanically jittering the offending components. In general the alignment of the optical components is critical. This often leads to complex and fragile designs with tight tolerances on optical component alignment, and can therefore be difficult and expensive to maintain in field instruments. This thesis pr.
Author: Yufei Ma
Publisher: MDPI
ISBN: 3039283987
Category : Technology & Engineering
Languages : en
Pages : 278
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Book Description
Trace gas sensing technologies are widely used in many applications, such as environmental monitoring, life science, medical diagnostics, and planetary exploration. On the one hand, laser sources have developed greatly due to the rapid development of laser media and laser techniques in recent years. Some novel lasers such as solid-state, diode, and quantum cascade lasers have experienced significant progress. At present, laser wavelengths can cover the range from ultraviolet to terahertz, which could promote the development of laser gas sensing technologies significantly. On the other hand, some new gas sensing methods have appeared, such as photothermal spectroscopy and photoacoustic spectroscopy. Laser spectroscopy-based gas sensing techniques have the advantages of high sensitivity, non-invasiveness, and allowing in situ, real-time observation. Due to the rapid and recent developments in laser source as well as the great merits of laser spectroscopy-based gas sensing techniques, this book aims to provide an updated overview of the state-of-the-art laser gas sensing technologies.
Author: Thomas Vallaitis
Publisher: KIT Scientific Publishing
ISBN: 3866447485
Category : Computers
Languages : en
Pages : 290
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Book Description
In this book, nonlinear silicon-organic hybrid waveguides and quantum dot semiconductor optical amplifiers are investigated. Advantageous applications are identified, and corresponding proof-of-principle experiments are performed. Highly nonlinear silicon-organic hybrid waveguides show potential for all-optical signal processing based on fourwave mixing and cross-phase modulation. Quantum dot semiconductor optical amplifiers operate as linear amplifiers with a very large dynamic range.
Author: René Bonk
Publisher: KIT Scientific Publishing
ISBN: 3866449569
Category : Technology & Engineering
Languages : en
Pages : 280
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Book Description
In this book, semiconductor optical amplifiers (SOAs) are studied with a view to linear and nonlinear applications in next-generation optical networks. Quantum-dot SOAs can be optimized for linear amplification of signals with different modulation formats and multiplexing techniques. Conversely, bulk SOAs can be easily optimized for operation in the nonlinear regime. However, due to the fast carrier recovery times in QD SOAs we also look into nonlinear applications with these devices.
Author: Luca Alloatti
Publisher: KIT Scientific Publishing
ISBN: 3731500566
Category : Technology (General)
Languages : en
Pages : 120
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Book Description
In this book, the first high-speed silicon-organic hybrid (SOH) modulator is demonstrated by exploiting a highly-nonlinear polymer cladding and a silicon waveguide. By using a liquid crystal cladding instead, an ultra-low power phase shifter is obtained. A third type of device is proposed for achieving three-wave mixing on the silicon-organic hybrid (SOH) platform. Finally, new physical constants which describe the optical absorption in charge accumulation/inversion layers in silicon are determined.
Author: Jingshi Li
Publisher: KIT Scientific Publishing
ISBN: 3866449577
Category : Technology & Engineering
Languages : en
Pages : 178
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Book Description
Self-coherent receivers are promising candidates for reception of 100 Gbit/s data rates in optical networks. Self-coherent receivers consist of multiple optical delay interferometers (DI) with high-speed photodiodes attached to the outputs. By DSP of the photo currents it becomes possible to receive coherently modulated optical signals. Especially promising for 100 Gbit/s networks is the PolMUX DQPSK format, the self-coherent reception of which is described in detail.
Author: R. Grisar
Publisher:
ISBN:
Category : Nature
Languages : en
Pages : 404
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Book Description
Divided into four sections, this work presents the proceedings of an international symposium on monitoring of gaseous pollutants by tunable diode lasers.
Author: James R. P. Bain
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Tunable diode laser spectroscopy is a widely used technique for recovering quantitative gas information in a range of industrial applications. Established methods often use readily available, robust and low cost optoelectronic hardware in the near-infrared, with output wavelengths that coincide with the absorption spectra of several important gas species of interest, providing a versatile platform for gas analysis instrumentation. In this work the challenges associated with the recovery of gas information from harsh detection environments, particularly for aero engine diagnostics, are considered. For stand-alone instrumentation, calibration-free direct absorption measurements are highly advantageous yet calibrated techniques employing wavelength modulation spectroscopy are often favoured due to their significantly higher sensitivities. Recent developments have enabled calibration-free line shape recovery using lock-in amplifier detection of the residual amplitude modulation in wavelength modulated signals. These techniques have significant potential in harsh environments, but the overall sensitivity is limited by distortions to the recovered line shapes at high modulation amplitudes and by large background signals that saturate the detection electronics. In this thesis, solutions to these two problems are proposed, investigated and validated. A correction function is derived that is able to account for line shape distortions at arbitrarily high modulation indices. Application of the function depends upon knowledge of the experimental modulation index and two methods for extracting this information directly from the experimental signals are described. The full correction procedure has been experimentally validated. An investigation was made into the use of autobalanced photoreceivers, typically used for common mode noise cancellation, for direct absorption measurements and in a different configuration for nulling of the residual amplitude modulation (RAM) in wavelength modulation spectroscopy. Initial measurements suggest that removal of the background RAM can increase the lock-in detection sensitivity by over an order of magnitude. In addition an external amplitude modulator has been iv shown to be an effective method for producing sensitive absorption signals that are free of distortions, recoverable at frequencies that are outside the bandwidth of most environmental noise sources. A temperature sensor based on ratio thermometry of ambient water vapour absorption was designed and evaluated. The sensor is intended to provide accurate intake gas temperature information during aero engine ground testing when misting conditions prevent standard thermocouples from providing reliable data. Direct detection and second harmonic wavelength modulation spectroscopy experiments were undertaken in an environmental chamber, over the range 273-313K, to test the potential accuracy of the proposed system. Using a second harmonic peak height method, temperature information based on a calibration was able to recover temperature measurements with precision of ±0.4K however the overall accuracy suffered from a problematic calibration drift. Three engine test campaigns are described in which a range of recovery methods and potential optical system layouts are evaluated for the purposes of intake and exhaust mounted test bed sensor systems. The effects of extreme noise conditions were observed on a variety of measurements and favourable detection and modulation options were identified for the purpose of planning proposed future engine tests. Exhaust plume measurements of high temperature water vapour on the Rolls-Royce Environmentally Friendly Engine demonstrator established the viability of temperature and concentration measurements up to 850K.
