共查询到20条相似文献,搜索用时 15 毫秒
1.
Daniel E. Vogler Ana Lorencak Julien M. Rey Markus W. Sigrist 《Optics and Lasers in Engineering》2005,43(3-5):527
A novel sensitive technique for the determination of losses in fiber cavities is presented. The method is based on the cavity ringdown scheme implemented in silica-based single-mode fibers. Bending losses of fiber cavities of different lengths have been measured showing all an oscillating behavior with respect to the curvature radius of the fiber as predicted by a theoretical model. The best minimum detectable absorbance per cavity pass achieved by this new method is 1.72×10−3 dB within a 10 m-long cavity. This limit suffices well for an accurate determination of optical bending losses even in bend-insensitive fibers. Furthermore, the comparison of the measured bending losses with a theoretical model allows the extraction of different fiber parameters. Good agreement has been found between the experimentally derived parameters and literature data. 相似文献
2.
-5 fractional absorption) and generality of IR-CRLAS for combustion studies is demonstrated for low pressure laminar flames
and is shown to be robust even in sooting environments with high temperature gradients. The ability to obtain (1-D) spatially
resolved spectra of both reactants and products within a narrow spectral region is also demonstrated. In these initial flame
studies, two information rich mid-infrared spectral regions are probed at Doppler-limited resolution, centered about 1.5 μm
and 3.3 μm.
Received: 30 August 1996 相似文献
3.
Andrey I. Meshkov 《Journal of Quantitative Spectroscopy & Radiative Transfer》2007,108(2):256-276
Fast scan submillimeter spectroscopy (FASSST) cavity ring down spectroscopy has been used to measure the dry air continuum, and separately its individual component parts, at ∼6000 frequencies in the spectral region between 170 and 260 GHz. These measurements have been made at pressures that range from 0 to 3 atmospheres and in the temperature range between 230 and 320 K. For several of the components these are the first measurements made at or near atmospheric conditions. These measurements contain all of the information necessary to parameterize the observed absorptions in terms of the fundamental line and continuum interactions without the need to import external parameters. The inversion of this analysis makes possible the calculation of atmospheric absorption with meaningful uncertainties over this spectral region for temperatures and pressures of atmospheric interest. 相似文献
4.
Thibault Desbois Irène Ventrillard Daniele Romanini 《Applied physics. B, Lasers and optics》2014,116(1):195-201
We present a scheme of optical feedback cavity-enhanced absorption spectroscopy (OF-CEAS) including a fast optical switch to produce cavity ringdown spectra (OF-CRDS) simultaneously. This also works as a dynamically adjustable variable attenuator allowing to compensate for reduced signal levels in correspondence with absorption lines. For this, an acousto-optic deflector is used in a double-pass configuration to eliminate the single-pass frequency shift, which is incompatible with optical feedback. This is probably the most effective device providing the required fast response and the high extinction ratio necessary to perform clean ringdown measurements. The resulting direct comparison of OF-CEAS and OF-CRDS shows that these produce almost equivalent spectral data, with 0.3 % maximal difference at the top of an absorption line having a signal-to-noise ratio (S/N) of 3,300. OF-CEAS is largely winning on the short-term noise level while OF-CRDS appears to be more immune from interference fringes, delivering cleaner spectra after longer averaging. 相似文献
5.
Fabio J. Mazzotti Lizandra Barrios Ranjini Raghunandan John P. Maier 《Molecular physics》2013,111(2):335-344
Theoretical quantitative considerations as well as experimental data are presented based on absorption population depletion coupled with cavity ringdown spectroscopy. The absorbing number densities inside the cavity are determined by numerical integration of the coupled rate equations. The number of photons involved in absorption, cavity losses due to mirror reflectivity and stimulated emission are taken into account. The principle is to monitor a first transition by cavity ringdown spectroscopy while a second transition, with a state in common, is resonantly excited by the decaying radiation of different frequency also trapped inside the optical cavity. A numerical example is given for atomic lines of neon and the measurements carried out in a supersonic slit-jet expansion discharge demonstrate the feasibility of the technique. The technique is also proven to work with two resonant transitions of C2. Translational velocity of the jet modifying the rate equations is included in the model. 相似文献
6.
针对传统腔衰荡光谱技术浓度获取率低,提出基于双重锁定的连续波腔衰荡吸收光谱技术.通过波长调制一次谐波信号将激光器的频率锁定到C_2H_2吸收线上,同时使用PDH锁频技术将衰荡腔锁定到激光器上,从而避免了测量过程中激光器的频率漂移和腔长的抖动,使测量结果更加精确;并且,由于双重锁定,单次衰荡事件的发生率,也就是浓度信息的获取率只受衰荡时间以及重新锁定时间限制,在本试验系统中采集速率可以达到30 k Hz,可以实现对气体浓度的快速测量.为了提高信噪比,采用Kalman滤波技术,对浓度信息进行实时处理,有效抑制了噪声,根据阿伦方差分析,探测灵敏度可以达到4×10~(-9)cm~(-1)(2 s平均). 相似文献
7.
A simple, economic diode laser based cavity ringdown system for trace-gas applications in the petrochemical industry is presented. As acetylene (C2H2) is sometimes present as an interfering contaminant in the gas flow of ethylene (ethene, C2H4) in a polyethylene production process, an on-line monitoring of such traces is essential. We investigated C2H2–C2H4 mixtures in a gas-flow configuration in real time. The experimental setup consists of a near-infrared external cavity diode laser with an output power of a few mW, standard telecommunication fibers and a home-made gas cell providing a user-friendly cavity alignment. A noise-equivalent detection sensitivity of 4.5×10-8 cm-1 Hz-1/2 was achieved, corresponding to a detection limit of 20 ppbV C2H2 in synthetic air at 100 mbar. In an actual C2H2–C2H4 gas-flow measurement the minimum detectable concentration of C2H2 added to the C2H4 gas stream (which may already contain an unknown C2H2 contamination) increased to 160 ppbV. Moreover, stepwise C2H2 concentration increments of 500 ppbV were resolved with a 1-min time resolution and an excellent linear relationship between the absorption coefficient and the concentration was found. PACS 07.07.Df; 42.62.Fi; 82.80.Gk 相似文献
8.
We perform a theoretical analysis on the transient dynamics of absorption saturation in pulsed cavity ringdown spectroscopy. Based on a coupled rate equation approach, modelling of the dynamic saturation is carried out to account for time-evolving intracavity photon density and absorbing population. Master equations are derived in terms of normalized system parameters, which enables one to systematically study the non-exponential feature of saturated cavity ringdown signals. Erroneous quantification of sample absorbance by the conventional ringdown time analysis is numerically simulated, and the saturated spectral feature showing a Lamb dip is obtained for a Doppler broadened sample. Finally a novel numerical recipe is proposed to handle saturated ringdown signals and retrieve unsaturated spectra, allowing relevant absorption parameters without degrading the measurement signal-to-noise ratio. PACS PACS 42.62.Fi; 42.60.Da 相似文献
9.
10.
For the exploration of gas hydrate resources by measuring the dissolved methane concentration in seawater, a continuous-wave cavity ringdown spectroscopy (CW-CRDS) experimental setup was constructed for trace methane detection. A current-modulation method, rather than a cavity-modulation method using an optical switch and a piezoelectric transducer, was employed to realize the cavity excitation and shutoff. Such a current-modulation method enabled the improvement of the experimental setup construction and stability, and the system size and stability are critical for a sensor to be deployed underwater. Ringdown data acquisition and processing were performed, followed by an evaluation of the experimental setup stability and sensitivity. The obtained results demonstrate that great errors are introduced when a large fitting window is selected if the analog-to-digital converter has an insufficient resolution. The ringdown spectrum of methane corresponding to the 2v 3 band R(4) branch was captured, and the methane concentration in lab air was determined to be 2.06 ppm. Further experiments for evaluating the quantitative ability of this CW-CRDS experimental setup are underway from which a high-sensitivity methane sensor that can be combined with a degassing system is expected. 相似文献
11.
J. Sato M. Kikukawa S. Yamaguchi M. Endo K. Tei K. Nanri T. Fujioka 《Applied physics. B, Lasers and optics》2009,96(4):741-744
A flexible and portable trace nitrogen dioxide sensor based on cavity ringdown spectroscopy using an optical fiber-coupled
high-finesse cavity was successfully demonstrated. Tailoring the spatial mode matching condition of the core of an optical
fiber and high-finesse external cavity allows for effective optical feedback into an antireflection-coated laser diode for
stable resonant enhancement of the external cavity. The external cavity, which works as a ringdown cavity, could be remotely
located from the light source and receiver section by only a single mode optical fiber. The sensitivity was found to be 1.0×10−7 cm−1 in a compact 1-cm3 ringdown cavity volume. 相似文献
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14.
A simple cavity ring-down technique employing a cw broadband diode laser is described for the reflectivity measurements of
highly reflective mirrors. Due to the broad line width of the diode laser, the laser beam can be continuously injected into
the ring-down cavity without tuning the cavity length or the laser frequency. Both Fourier- and time-domain data-processing
approaches are developed to determine the reflectivity. In the Fourier domain, the amplitudes and phase shifts of the first
and third harmonics of a periodic ring-down signal are measured as a function of the modulation frequency covering an appropriate
range. The cavity decay time and the reflectivity of the cavity mirror are determined by minimizing a mean square variance
containing both the amplitude and phase-shift error terms. On the other hand, in the time domain, the cavity decay time and
the instrumental response time are determined simultaneously by fitting the measured waveforms of the cavity ring-down signals
to a rigorous time-domain model via a multi-parameter fitting procedure. The reflectivity measurements are repeated at four
cavity lengths and all the results obtained with both data-processing approaches are in excellent agreement. The reflectivity
of cavity mirrors near 830 nm is statistically determined to be 0.99797 with an uncertainty less than 3×10-5.
PACS 07.60.Hv; 42.60.Da; 42.55.Px 相似文献
15.
Optical absorption spectrum of gold atoms deposited on SiO(2) from cavity ringdown spectroscopy 总被引:1,自引:0,他引:1
Antonietti JM Michalski M Heiz U Jones H Lim KH Rösch N Vitto AD Pacchioni G 《Physical review letters》2005,94(21):213402
The optical properties of gold atoms supported on amorphous silica (alpha-SiO2) were studied experimentally and theoretically in the visible range. Samples were prepared in situ by depositing Au atoms at low coverages (5 x 10(12) cm(-2)) in UHV, and the optical absorption spectra were recorded by cavity ringdown spectroscopy. The atomic absorption bands can be attributed to gold atoms trapped at [triple bond] Si-O(.-) and [triple bond]Si-O(-) defect sites. The absence of optical transitions typical for Au(2) shows that the atoms are efficiently anchored at these defect sites, preventing diffusion and aggregation. Furthermore, these experimental results reveal that it is now possible to study optical properties of well-defined nanostructures at surface coverages as low as 5 x 10(11) cm(-2). 相似文献
16.
The dye-laser amplified absorption method is applied to observe the atomic absorption lines of rare-earth elements in a nitrous-oxide-acetylene flame. All of the rare-earth elements except Pm are analyzed and about 1200 lines have been recorded within the continuous spectral region from 432 to 670 nm. A much larger number of absorption lines can be detected than those measured by the traditional method. The absorption bands of monoxide molecules have also been detected. 相似文献
17.
P. A. Bonczyk 《Applied Physics A: Materials Science & Processing》1975,6(1):125-126
The power of a HF laser versus cavity frequency is measured in the presence of saturable HF gas. A resonant power maximum is observed which is relevant to laser frequency stabilization and molecular line broadening measurement. 相似文献
18.
S. A. Babin D. V. Churkin A. E. Ismagulov S. I. Kablukov E. V. Podivilov 《Laser Physics》2007,17(11):1279-1285
Intracavity and output spectra broadened in a Raman fiber laser with a low-Q cavity are measured and theoretically described. It is demonstrated that the previously developed approach of optical-wave turbulence can be used to describe the spectral broadening owing to the multiple four-wave mixing processes that involves numerous longitudinal modes of the low-Q cavity. The theoretically calculated spectra are in good agreement with the experimental data for various output reflection coefficients of the fiber Bragg gratings across the entire power range. 相似文献
19.
A novel precise force measurement based on a Y-shaped cavity dual-frequency laser is proposed.The principle of force measurement with this method is analyzed,and the analytic relation expression between the input force and the change in the output beat frequency is derived.Experiments using a 632.8-nm Y-shaped cavity He-Ne dual-frequency laser are then performed;they demonstrate that the force measurement is proportional to a high degree over almost five decades of input signal range.The maximum scale factor is observed as 5.02×109 Hz/N,with beat frequency instability equivalent resolution of 10-5 N.By optimizing the optical and geometrical parameters of the laser sensor,a force measurement resolution of 10-6 N could be expected. 相似文献
20.
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