共查询到20条相似文献,搜索用时 15 毫秒
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Kevin K. Lehmann 《Applied physics. B, Lasers and optics》2014,116(1):147-155
Giusfredi et al. (Phys Rev Lett 104, 110801, 2010), have developed a new approach to cavity ring-down spectroscopy where a saturable sample absorption is determined simultaneously with the cavity loss, providing immunity to changes in cavity loss, thereby allowing for lower analyte detection limit. This paper presents an error analysis that provides predictions of the ultimate sensitivity limits that can be realized with this detection method. In particular, the sensitivity is strongly dependent upon the initial degree of saturation of the sample, and optimal values for this are determined both for photon detector and shot-noise-limited detection of both inhomogeneous and homogeneous broadened spectroscopic lines. Also presented are sensitivity limits expected for two-photon absorption spectroscopy determined by cavity ring-down spectroscopy. 相似文献
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Intracavity laser absorption spectroscopy (ICLAS) and cavity ring-down spectroscopy (CRDS) have been used for measurement of the NH2-radical spectrum near 643 nm. NH2 was obtained in low-pressure methane/air flat flames doped with minor amounts of ammonia (as low as 0.023%). The NH2 concentration was measured both by CRDS and ICLAS in the same conditions. This enables us to compare the practical sensitivity of the two methods. Both methods were also used for measurements in a sooting acetylene/air flame (ϕ = 2.6). The comparative advantages of the methods and their complementarities are discussed. 相似文献
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A. Cygan S. Wójtewicz J. Domysławska P. Masłowski K. Bielska M. Piwiński K. Stec R. S. Trawiński F. Ozimek C. Radzewicz H. Abe T. Ido J. T. Hodges D. Lisak R. Ciuryło 《The European physical journal. Special topics》2013,222(9):2119-2142
A review of recent experiments involving a newly developed Pound-Drever-Hall-locked frequency-stabilized cavity ring-down spectroscopy (PDH-locked FS-CRDS) system is presented. By comparison to standard FS-CRDS, the PDH lock of the probe laser to the ring-down cavity optimized coupling into the cavity, thus increasing the ring-down signal acquisition rate nearly 300-fold to 14 kHz and reducing the noise-equivalent absorption coefficient by more than an order of magnitude to 7 × 10?11 cm?1. We discuss how averaging approximately 1000 spectra yielded a signal-to-noise ratio of 220000. We also discuss how the spectrum frequency axis was linked to an optical frequency comb, thus enabling absolute frequency measurements of molecular optical transitions at sub-MHz levels. Applications of the spectrometer to molecular line-shape studies are also presented. For these investigations, we use semi-classical line-shape models that consider the influence of Dicke narrowing as well as the speed dependence of the pressure broadening and shifting to fit spectra. We show that the improved precision and spectrum fidelity of the spectrometer enable precise determinations of line-shape parameters. We also discuss the importance of line-shape analysis with regard to the development of new spectroscopic databases as well as in the optical determination of the Boltzmann constant. 相似文献
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腔振铃激光吸收光谱技术是近年快速发展的一项新颖的光谱技术,它不仅检测灵敏度高,而且结构简单,不需要高昂的光谱设备,特别适合于测量弱吸收物质,包括气体、固体、液体等稳态粒子和金属化合物、自由基、团簇等瞬态粒子.本文在介绍其基本原理的基础上,介绍了使用脉冲激光与连续激光光源的2种技术方案. 相似文献
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We achieve a quantum-noise-limited absorption sensitivity of 1.7×10(-12) cm(-1) per spectral element at 400 s of acquisition time with cavity-enhanced frequency comb spectroscopy, the highest demonstrated for a comb-based technique. The system comprises a frequency comb locked to a high-finesse cavity and a fast-scanning Fourier transform spectrometer with an ultralow-noise autobalancing detector. Spectra with a signal-to-noise ratio above 1000 and a resolution of 380 MHz are acquired within a few seconds. The measured absorption line shapes are in excellent agreement with theoretical predictions. 相似文献
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为实现连续波腔衰荡光谱系统的工程化,设计了一套集信号调理、高速采样及数据处理为一体的高集成度数字信号处理(DSP)系统。该系统被用于取代常规连续波腔衰荡光谱系统中由高速数据采集卡及计算机组成的腔衰荡信号测试系统,完成对腔衰荡信号的获取与拟合。该系统最高能实现16 bits/80 MHz的信号采样,并能准确地由腔衰荡信号反演出腔衰荡时间。实验结果表明:结合现有的光反馈式连续波腔衰荡光谱系统,该系统能实现等噪声测量灵敏度为1.0×10-8 cm-1的吸收光谱测量,其重复测量精度可达3‰。 相似文献
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为实现连续波腔衰荡光谱系统的工程化,设计了一套集信号调理、高速采样及数据处理为一体的高集成度数字信号处理(DSP)系统。该系统被用于取代常规连续波腔衰荡光谱系统中由高速数据采集卡及计算机组成的腔衰荡信号测试系统,完成对腔衰荡信号的获取与拟合。该系统最高能实现16 bits/80 MHz的信号采样,并能准确地由腔衰荡信号反演出腔衰荡时间。实验结果表明:结合现有的光反馈式连续波腔衰荡光谱系统,该系统能实现等噪声测量灵敏度为1.0×10-8 cm-1的吸收光谱测量,其重复测量精度可达3‰。 相似文献
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David J. Robichaud Daniel Lisak Charles E. Miller 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(3):435-444
We describe a high-precision method for measuring pressure shifting of absorption lines. The technique involves the acquisition of high-resolution spectra using a cavity ring-down spectrometer whose length is continuously locked to a frequency-stabilized reference laser over a range of sample pressures. We discuss a relatively large correction arising from the pressure-dependence of dispersion in the cavity modes, and we demonstrate pressure shifting measurements in air for transitions in the 16O2A-band. Pressure shifts in the range -0.011 to are reported. We measured relative positions of line centers to within 70 kHz and determined pressure shifting coefficients over a 5 kPa pressure range with relative uncertainties approximately equal to 1.0%, which constitutes a five-fold improvement over previous measurements. 相似文献
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D. A. Long M. Okumura C. E. Miller J. T. Hodges 《Applied physics. B, Lasers and optics》2011,105(2):471-477
Carbon dioxide (CO2) isotopic ratios on samples of pure CO2 were measured in the 1.6 μm wavelength region using the frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) technique.
We present CO2 absorption spectra with peak signal-to-noise ratios as high as 28,000:1. Measured single-spectrum signal-to-noise ratios
were as high as 8900:1, 10,000:1, and 1700:1 for 13C/12C, 18O/16O, and 17O/16O, respectively. In addition, we demonstrate the importance of utilizing the Galatry line profile in the spectrum analysis.
The use of the Voigt line profile, which neglects the observed collisional narrowing, leads to large systematic errors which
are transition-dependent and vary with temperature and pressure. While the relatively low intensities of CO2 transitions near λ=1.6 μm make this spectral region non-optimal, the sensitivity and stability of FS-CRDS enabled measurement precision of pure
CO2 samples which are comparable to those of other optical techniques which operate at far more propitious wavelengths. These
results indicate that a FS-CRDS spectrometer designed to probe CO2 bands near wavelengths of 2.0 μm or 4.3 μm could achieve significantly improved precision over the present instrument and
likely be competitive with mass spectrometric methods. 相似文献
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K. E. Whittaker L. Ciaffoni G. Hancock P. L. Hurst R. Peverall G. A. D. Ritchie 《Applied physics. B, Lasers and optics》2014,116(1):157-168
Studies into the suitability of a novel, widely tunable telecom L-band (1,563–1,613 nm) digital supermode distributed Bragg reflector (DS-DBR) laser for cavity ring-down spectroscopy (CRDS) are presented. The spectrometer comprised of a 36.6?cm long linear cavity with ring-down times varying between 19–26 μs across the 50 nm DS-DBR wavelength range due to changes in the cavity mirror reflectivities with wavelength. The potential of such a broadband, high-resolution CRD spectrometer was illustrated by investigating several transitions of CO2 in air, a 5 % calibrated mixture and breath samples. Allan variance measurements at a single wavelength indicated an optimal minimum detectable absorption coefficient (α min) of 3 × 10?10 cm?1 over 20 s. 相似文献
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Molecular oxygen detection in low pressure flames using cavity ring-down spectroscopy 总被引:1,自引:0,他引:1
Cavity ring down spectroscopy is used for measurement of the concentration profiles of oxygen in the low pressure (30 Torr) methane/nitrogen/oxygen flames. Three different equivalence ratios are used: 0.8, 1.0 and 1.17. Molecular oxygen concentration is monitored via rotational spectrum of b1
Σ
g
+←X3
Σ
g
- (v′=0-v′′=0) transition, also known as atmospheric A band, located near 750 nm. The P(15)P(15) line is used for concentration measurements. The sensitivity reached is 2.2×10-8 cm-1. The concentration profiles are in a good agreement with the ones calculated using GRI-3.0 mechanism. PACS 33.20.Kf; 33.70.Fd; 42.60.Da 相似文献
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High-sensitivity methane monitoring based on quasi-fundamental mode matched continuous-wave cavity ring-down spectroscopy 下载免费PDF全文
Continuous-wave cavity ring-down spectroscopy (CW-CRDS) is an important technical means to monitor greenhouse gases in atmospheric environment. In this paper, a CW-CRDS system is built to meet the needs of atmospheric methane monitoring. The problem of mode matching is explained from the perspective of transverse mode and longitudinal mode, and the influence of laser injection efficiency on measurement precision is further analyzed. The results of cavity ring-down time measurement show that the measurement precision is higher when the laser is coupled with the fundamental mode. In the experiment, DFB laser is used to calibrate the system with standard methane concentration, and the measurement residual is less than ±4×10-4 μs-1. The methane concentration in the air is monitored in real time for two days. The results show the consistency of the concentration changes over the two days, which further demonstrates the reliability of the system for the measurement of trace methane. By analyzing the influence of mode matching, it not only assists the adjustment of the optical path, but also further improves the sensitivity of the system measurement. 相似文献
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基于谐振腔失调灵敏度参量随腔长的变化关系,提出了一种衰荡腔,它是由共焦腔将腔长缩短为原来的0.73得到的稳定腔。根据光束传输规律和失调腔矩阵方法,以及光腔衰荡法测量原理和曲线拟合方法,建立了腔长、腔镜角度失调下光腔衰荡法的反射率测量模型。通过数值模拟,研究了这种稳定衰荡腔中,腔微小失调对反射率测量结果的影响,并与相同失调情况下共焦衰荡腔的测量结果进行了对比分析。结果表明,这种稳定腔用作衰荡腔,测量结果受腔镜角度失调影响较大,而受腔长失调影响小;其长度较短,便于工程应用;衍射损耗较小,测量精度高。 相似文献
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J. Peltola M. Vainio V. Ulvila M. Siltanen M. Metsälä L. Halonen 《Applied physics. B, Lasers and optics》2012,107(3):839-847
We demonstrate an off-axis cavity ring-down spectroscopy system, which uses a mid-infrared continuous-wave optical parametric oscillator as a light source. Off-axis injection with re-entrant configuration of the ring-down cavity is used to achieve high spectral resolution while maintaining high measurement speed. This makes the setup suitable for sensitive molecular spectroscopy in the mid-infrared region, particularly for studies that require high temporal resolution. Formaldehyde (H2CO) absorption spectrum at 3.4 µm is measured using the off-axis re-entrant cavity ring-down spectrometer. 相似文献