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1.
Kasyutich V.L. Bale C.S.E. Canosa-Mas C.E. Pfrang C. Vaughan S. Wayne R.P. 《Applied physics. B, Lasers and optics》2003,76(6):691-697
We present an application of cavity-enhanced absorption spectroscopy with an off-axis alignment of the cavity formed by two
spherical mirrors and with time integration of the cavity-output intensity for detection of nitrogen dioxide (NO2) and iodine monoxide (IO) radicals using a violet laser diode at λ=404.278 nm. A noise-equivalent (1σ≡ root-mean-square variation
of the signal) fractional absorption for one optical pass of 4.5×10-8 was demonstrated with a mirror reflectivity of ∼0.99925, a cavity length of 0.22 m and a lock-in-amplifier time constant
of 3 s. Noise-equivalent detection sensitivities towards nitrogen dioxide of 1.8×1010 molecule cm-3 and towards the IO radical of 3.3×109 molecule cm-3 were achieved in flow tubes with an inner diameter of 4 cm for a lock-in-amplifier time constant of 3 s. Alkyl peroxy radicals
were detected using chemical titration with excess nitric oxide (RO2+NO→RO+NO2). Measurement of oxygen-atom concentrations was accomplished by determining the depletion of NO2 in the reaction NO2+O→NO+O2. Noise-equivalent concentrations of alkyl peroxy radicals and oxygen atoms were 3×1010 molecule cm-3 in the discharge-flow-tube experiments.
Received: 4 February 2003 / Revised version: 10 March 2003 / Published online: 12 May 2003
RID="*"
ID="*"Corresponding author. Fax: +44-1865/275-410, E-mail: vlk@physchem.ox.ac.uk 相似文献
2.
Rapid formaldehyde monitoring in ambient air by means of mid-infrared cavity leak-out spectroscopy 总被引:1,自引:0,他引:1
H. Dahnke G. von Basum K. Kleinermanns P. Hering M. Mürtz 《Applied physics. B, Lasers and optics》2002,75(2-3):311-316
We report the spectroscopic detection of formaldehyde in ambient air using cavity leak-out spectroscopy, a cw variant of cavity
ring-down spectroscopy. This technique proved to be suitable for a real-time quantitative analysis of polluted air without
any preprocessing of the air sample. Using a tunable CO-overtone sideband laser for the λ=3 μm spectral region and a ring-down
cell with R=99.95% mirrors, we achieved a detection limit of 2 parts per billion formaldehyde in ambient air, corresponding
to a minimum detectable absorption coefficient of 7×10-9/cm (sampling time: 2 s). Calibration problems arising from the polarity of the molecule and due to HITRAN database uncertainties
are discussed.
Received: 28 March 2002 / Revised version: 7 June 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +49-211/811-3121, E-mail: muertz@uni-duesseldorf.de 相似文献
3.
B. Bakowski L. Corner G. Hancock R. Kotchie R. Peverall G.A.D. Ritchie 《Applied physics. B, Lasers and optics》2002,75(6-7):745-750
Cavity-enhanced absorption spectroscopy is explained in terms of the transmission function of a rapidly swept interferometer,
and the integrated transmission is shown to be proportional to the cavity ringdown time. The technique is demonstrated on
the b1Σg
+-X3Σg
- (1,0) band in molecular oxygen at 687 nm using a tunable diode laser and a relative-ly high-Q optical cavity (finesse ≈4000).
A detection limit of 3×10-8 cm-1 s1/2 is achieved for a 0.8 cm-1 scanning range.
Received: 24 June 2002 / Revised version: 5 August 2002 / Published online: 15 November 2002
RID="*"
ID="*"Corresponding author. Fax: +44-1865/275410, E-mail: peverall@physchem.ox.ac.uk 相似文献
4.
Sensitive absorption measurements in the near-infrared region using off-axis integrated-cavity-output spectroscopy 总被引:3,自引:0,他引:3
A novel instrument that employs a high-finesse optical cavity as an absorption cell has been developed for sensitive measurements
of gas mixing ratios using near-infrared diode lasers and absorption-spectroscopy techniques. The instrument employs an off-axis
trajectory of the laser beam through the cell to yield an effective optical path length of several kilometers without significant
unwanted effects due to cavity resonances. As a result, a minimum detectable absorption of approximately 1.4×10-5 over an effective optical path of 4.2 km was obtained in a 1.1-Hz detection bandwidth to yield a detection sensitivity of
approximately 3.1×10-11 cm-1 Hz-1/2. The instrument has been used for sensitive measurements of CO, CH4, C2H2 and NH3.
Received: 6 May 2002 / Revised version: 31 May 2002 / Published online: 2 September 2002
RID="*"
ID="*"Corresponding author. Fax: +1-650/965-7074, E-mail: d.baer@lgrinc.com 相似文献
5.
V.L. Kasyutich P.A. Martin R.J. Holdsworth 《Applied physics. B, Lasers and optics》2006,85(2-3):413-420
A distributed feedback diode laser sensor based upon off-axis cavity-enhanced absorption spectroscopy at 1605.5 nm has been developed for 13C16O2/12C16O2 isotope ratio measurements in synthetic air and human breath. A noise-equivalent absorption sensitivity of 3.9×10-10 cm-1 Hz-1/2 has been determined for a cavity base length of 28.2 cm and averaging 4000 scans within 8.688 s. For 5% CO2 concentration measurements, δ13C standard deviations of 1.8 ‰ and 3.7 ‰ have been estimated for five successive measurements based on peak height and integrated area estimations at 107.9 Torr, respectively. The contributions of amplified spontaneous emission of the laser and a radiation that is spatially uncoupled into the cavity mode have been described for cavity transmittance measurements. The limitations of the developed sensor and further steps towards precision and accuracy improvements are discussed. PACS 42.55.Px; 39.30.+w; 42.62.Fi; 42.60.-v 相似文献
6.
Portable difference-frequency laser-based cavity leak-out spectrometer for trace-gas analysis 总被引:1,自引:0,他引:1
We report a portable mid-infrared spectrometer for trace-gas analysis which is based on an all-solid-state difference-frequency-generation
laser. The spectrometer provides in situ absorption path lengths of more than 3 km by means of the cavity leak-out method,
a cw variant of the cavity ring-down technique. The design, performance, and application of this spectrometer are presented.
The light source utilizes difference-frequency generation in a periodically poled lithium niobate (PPLN) crystal pumped by
two single-frequency solid-state lasers. A maximum power of 27 μW in the wavelength region near 3.3 μm is achieved using a
pump power of 20 mW at 808 nm, a signal power of 660 mW at 1064 nm, and a 50-mm-long PPLN crystal. This corresponds to a conversion
efficiency of 0.42 mW/(W2 cm). We demonstrate that this portable laser system is suitable as a light source in a cavity leak-out spectrometer. We achieved
a minimum detectable absorption coefficient of 1×10-8/cm (integration time: 2 s), corresponding, for example, to a detection limit of 1 part per billion ethane. This compact trace-gas
analyzer with high sensitivity and specificity is promising for various environmental and medical applications.
Received: 8 April 2002 / Revised version: 28 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +49-211/811-3121, E-mail: muertz@uni-duesseldorf.de 相似文献
7.
D.D. Nelson J.H. Shorter J.B. McManus M.S. Zahniser 《Applied physics. B, Lasers and optics》2002,75(2-3):343-350
Non-cryogenic, laser-absorption spectroscopy in the mid-infrared has wide applications for practical detection of trace gases
in the atmosphere. We report measurements of nitric oxide in air with a detection limit less than 1 nmole/mole (<1 ppbv) using
a thermoelectrically cooled quantum cascade laser operated in pulsed mode at 5.26 μm and coupled to a 210-m path length multiple-pass
absorption cell at reduced pressure (50 Torr). The sensitivity of the system is enhanced by operating under pulsing conditions
which reduce the laser line width to 0.010 cm-1 (300 MHz) HWHM, and by normalizing pulse-to-pulse intensity variations with temporal gating on a single HgCdTe detector.
The system is demonstrated by detecting nitric oxide in outside air and comparing results to a conventional tunable diode
laser spectrometer sampling from a common inlet. A detection precision of 0.12 ppb Hz-1/2 is achieved with a liquid-nitrogen-cooled detector. This detection precision corresponds to an absorbance precision of 1×10-5 Hz-1/2 or an absorbance precision per unit path length of 5×10-10 cm-1 Hz-1/2. A precision of 0.3 ppb Hz-1/2 is obtained using a thermoelectrically cooled detector, which allows continuous unattended operation over extended time periods
with a totally cryogen-free instrument.
Received: 1 May 2002 / Revised version: 6 June 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +1-978/663-4918, E-mail: ddn@aerodyne.com 相似文献
8.
Spectroscopic sensing of gases can be performed with high sensitivity and photometric precision by cavity ringdown (CRD) absorption
spectroscopy. Our cavity ringdown spectrometer incorporates continuous-wave (cw) tunable diode lasers, fibre-optic coupling
and standard photonics and optical telecommunications components. It comprises a rapidly swept optical cavity in a single-ended
optical heterodyne transmitter–receiver configuration, enabling optical absorption of gases to be recorded either as single-frequency
scanned spectra or as simultaneous, multi-wavelength tailored spectra. By measuring weak near-infrared rovibrational spectra
of carbon dioxide gas (CO2), with high resolution in the vicinity of 1.53 μm, we have realised a noise-limited absorption sensitivity of 2.5×10-9 cm-1 Hz-1/2. Analytical sensitivity limits (both actual and projected) and prospective gas-diagnostic applications are discussed. Our
approach to cw-CRD spectroscopy offers high performance in a relatively simple, low-cost, compact instrument that is amenable
to chemical analysis of trace gases in medical, agricultural, industrial and environmental situations.
Received: 16 May 2002 / Revised version: 3 June 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +61-2/9850-8313, E-mail: brian.orr@mq.edu.au 相似文献
9.
Wavelength-modulation spectroscopy using a frequency-doubled current-modulated diode laser 总被引:1,自引:0,他引:1
We have studied atomic absorption in an argon discharge by wavelength-modulation spectroscopy with a frequency-doubled diode
laser. The tunable wavelength-modulated radiation at 430 nm was generated by frequency doubling a current-modulated 860-nm
diode laser in a KNbO3 crystal. 2f-, 4f- and 6f-harmonic spectra as a function of diode laser modulation depth were measured on a Doppler-broadened
sample of excited argon atoms produced in a capacitively coupled plasma chamber. Characterisation of the harmonic signals
was accomplished. Minimum detectable absorbances of 7.7×10-5 and 1.9×10-4 based on a 3σ criterion (σ being the standard deviation of the noise) were estimated for 2f- and 4f-harmonic detection of
the frequency-doubled radiation with a time constant of 0.1 s. The concentrations of argon in the 1s4 state were found to be in the range of 3×108 to 1.2×1011 cm-3 for the experimental conditions studied.
Received: 25 February 2002 / Revised version: 4 April 2002 / Published online: 14 May 2002 相似文献
10.
M.B. Pushkarsky M.E. Webber O. Baghdassarian L.R. Narasimhan C.K.N. Patel 《Applied physics. B, Lasers and optics》2002,75(2-3):391-396
An industrial trace-ammonia sensor based on photoacoustic spectroscopy and CO2 lasers has been developed for measuring ammonia with a 1σ detection limit of 220 parts-per-trillion (ppt) in an integration
time of 30 s. The instrument response time for measuring ammonia was 200 s, limited by adsorption effects due to the polar
nature of ammonia. The minimum detectable fractional absorbance was 2.0×10-7, and the minimum normalized detectable absorption coefficient for this system was 2.4×10-7 W cm-1/z. The 9R(30) transition of the CO2 laser at 9.22 μm with 2 W of output power was used to probe the strong sR(5,K) multiplet of ammonia at the same wavelength. This sensor was demonstrated with an optically multiplexed configuration
for simultaneous measurement in four cells.
Received: 3 April 2002 / Revised version: 31 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +1-310/458-0171, E-mail: webber@pranalytica.com 相似文献
11.
We present a portable spectrometer that uses the frequency-stabilized cavity ring-down spectroscopy technique capable of high-precision measurements of trace water vapor concentration. Measuring one of the strongest rovibrational transitions in the ν1+ν3 water vapor combination band near ˜ν=7181.156 cm-1, we compare spectroscopic and thermodynamic determinations of trace water vapor in N2, and find systematic differences attributable to water vapor background effects and/or uncertainties in line intensities. We also compare the frequency-stabilized ring-down method with other cavity ring-down approaches that are based on unstabilized probe lasers and unstabilized ring-down cavities. We show that for the determination of water vapor concentration, the frequency-stabilized cavity ring-down method has the minimum measurement uncertainty of these techniques. The minimum noise-equivalent absorption coefficient of the spectrometer was 1.2×10-10 cm-1 Hz-1/2, which further corresponds to a minimum detectable water vapor mole fraction equal to 0.7×10-9 for an absorption spectrum of 10 minutes duration. PACS 33.20.-t; 33.70.Jg; 33.70.Fd; 42.62.Fi 相似文献
12.
A tunable diode laser photoacoustic setup based on a recently demonstrated cantilever technique was used for sensitive detection of oxygen. As light sources, we used a distributed feedback (DFB) diode laser and a vertical-cavity surface-emitting (VCSEL) laser, both operating near 760 nm. With the 30 mW DFB laser a noise-equivalent detection limit of 20 ppm for oxygen was obtained, while a detection limit of 5 ‰ was achieved with the VCSEL having an output power of 0.5 mW. Our results yield a noise-equivalent sensitivity of 4.8×10-9 cm-1W Hz-1/2 and demonstrate the potential of this technique for compact and sensitive measurement of oxygen. PACS 42.62.Fi; 42.55.Px; 82.80.Kq 相似文献
13.
We report on monitoring of nitric oxide (NO) traces in human breath via infrared cavity leak-out spectroscopy. Using a CO
sideband laser near 5 μm wavelength and an optical cavity with two high-reflectivity mirrors (R=99.98%), the minimum detectable absorption is 2×10−10 cm−1 Hz1/2. This allows for spectroscopic analysis of rare NO isotopologues with unprecedented sensitivity. Application to simultaneous
online detection of 14NO and 15NO in breath samples collected in the nasal cavity is described for the first time. We achieved a noise-equivalent detection
limit of 7 parts per trillion for nasal 15NO (integration time: 70 s). 相似文献
14.
W. Zhao X. Gao W. Chen W. Zhang T. Huang T. Wu H. Cha 《Applied physics. B, Lasers and optics》2007,86(2):353-359
A novel instrument based on an improved off-axis alignment of integrated cavity output spectroscopy (OA-ICOS) in conjunction
with a wavelength modulation (WM) technique, was developed using a DFB diode laser operating in the near infrared at 1.573 μm
(6357.3 cm-1). The laser-based sensor employed a 44 cm optical cavity that provided an effective absorption path length of ∼68 m. A minimum
detectable absorption of approximately 3.6 ppmv Hz-1/2 or 2.3×10-7 Hz-1/2 per optical pass was obtained using second harmonic detection. We demonstrated that by implementation of the WM technique
to OA-ICOS in the near infrared, the detection sensitivity was improved by a factor of 14 compared to that obtained with OA-ICOS.
Measurements of CO2 mixing ratios in ambient air have been performed by using both OA-ICOS and WM-OA-ICOS techniques for performance comparison.
PACS 42.62.Fi; 07.07.Df; 33.20.Ea 相似文献
15.
L. Ciaffoni B. L. Cummings W. Denzer R. Peverall S. R. Procter G. A. D. Ritchie 《Applied physics. B, Lasers and optics》2008,92(4):627-633
High resolution diode laser spectroscopy has been applied to the detection of hydrogen sulphide at ppm levels utilizing different
transitions within the region of the ν
1+ν
2+ν
3 and 2ν
1+ν
2 combination bands around 1.58 μm. Suitable lines in this spectral region have been identified, and absolute absorption cross
sections have been determined through single-pass absorption spectroscopy and confirmed in the Doppler linewidth regime using
cavity enhanced absorption spectroscopy (CEAS). The desire for a sensitive system potentially applicable to H2S sensing at atmospheric pressure has led to an investigation on suitable transitions using wavelength modulation spectroscopy
(WMS). The set-up sensitivity has been calculated as 1.73×10−8 cm−1 s1/2, and probing the strongest line at 1576.29 nm a minimum detectable concentration of 700 ppb under atmospheric conditions
has been achieved. Furthermore, pressure broadening coefficients for a variety of buffer gasses have been measured and correlated
to the intermolecular potentials governing the collision process; the H2S–H2S dimer well depth is estimated to be 7.06±0.09 kJ mol−1. 相似文献
16.
M. L. Hamilton R. Peverall G. A. D. Ritchie L. J. Thornton J. H. van Helden 《Applied physics. B, Lasers and optics》2009,97(3):715-722
We have demonstrated the production of ∼1.9 μm near-infrared radiation by using difference frequency generation within a 5%
MgO doped PPLN crystal by coupling ∼735 nm radiation from a tunable external cavity diode laser with relatively high powered
532 nm radiation from both Nd:YVO3 and Nd:YAG lasers. The radiation produced is of low power, ∼15 μW, and was used in conjunction with the sensitivity enhancing
techniques of wavelength modulation spectroscopy (WMS) and cavity enhanced absorption spectroscopy (CEAS). Experiments were
carried out on rotationally resolved transitions in the combination bands of NH3 and CO2 in the 1.9 μm region. An α
min value of 3.6×10−6 cm−1 Hz−1/2 was achieved for WMS measurements on CO2. A comparable α
min value of 2.2×10−6 cm−1 Hz−1/2 was achieved for NH3 using CEAS. The low NIR power indicates that despite the level of MgO doping quoted for the crystal, under prolonged exposure
photorefractive damage has occurred. 相似文献
17.
A.V. Podlipensky K.V. Yumashev N.V. Kuleshov H.M. Kretschmann G. Huber 《Applied physics. B, Lasers and optics》2003,76(3):245-247
Spectroscopic data of a V3+:YAG passive Q-switch crystal were measured. The absorption recovery time was determined to be of 37±7 ns and the ground state
absorption cross section was estimated to be 0.7×10-18 cm2 at 1.44 μm and 3.5×10-18 cm2 at 1.34 μm. Passively Q-switched operation of diode pumped 1.44 μm and 1.3 μm Nd:YAG lasers was demonstrated using this crystal
as saturable absorber. Average output powers of 1.42 W (1.44 μm) and 1.56 W (1.34 μm) and pulse energies of 24 μJ (1.44 μm)
and 25 μJ (1.34 μm) were observed, respectively.
Received: 19 August 2002 / Published online: 12 February 2003
RID="*"
ID="*"Corresponding author. Fax: +49-40/42838-6281, E-mail: kretschmann@physnet.uni-hamburg.de 相似文献
18.
Cavity ringdown (CRD) spectroscopy, with its high sensitivity, provides a novel way to perform continuous-wave (cw) stimulated
Raman gain (SRG) spectroscopy, rather than by conventional optically detected coherent Raman techniques. Tunable cw laser
light at ∼1544 nm is used to probe ringdown decay from a rapidly-swept, high-finesse optical cavity containing a gas-phase
sample of interest and itself located inside the cavity of a cw single-longitudinal-mode Nd:YAG ring laser operating at ∼1064.4
nm. This approach is used to measure cw SRG spectra of the ν
1 fundamental rovibrational Raman band of methane gas at ∼2916.5 cm−1. The resulting SRG-CRD resonances have ringdown times longer than in the off-resonance case, in contrast to the usual shorter
ringdown times arising from absorption and other loss processes. Previously reported noise-equivalent sensitivities have been
substantially improved, by using a second ringdown cavity to facilitate subtraction of infrared-absorption background signals.
Moreover, by employing a ringdown cavity in the form of a ring, the SRG-pump and CRD-detected Stokes beams can co-propagate
uni-directionally, which significantly reduces Doppler broadening. 相似文献
19.
A pulsed optical parametric oscillator (OPO) operated in an optical cavity with a grazing-incidence grating configuration
(GIOPO) was used for sensitive photoacoustic detection of trace quantities of dinitrogen oxide (N2O). The (ν1+ν3) combination vibration band of N2O was excited with the idler beam of the GIOPO at 2.86 μm using an optical cavity optimized for the idler beam. The linewidth
of the GIOPO could be reduced to 0.4 cm-1, allowing the rotational structure of the absorption spectrum to be resolved. A concentration sensitivity (signal-to-noise
ratio=3) of 60 parts in 109 by volume (60 ppb V) N2O in synthetic air was obtained. This may be sufficient for continuous monitoring of N2O in the atmosphere.
Received: 29 April 2002 / Revised version: 4 June 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +49-6221/54-4255, E-mail: peter.hess@urz.uni-heidelberg.de 相似文献
20.
A. D. Khrycheva D. A. Nedosekin M. Yu. Kononets M. A. Proskurnin S. V. Pakhomova W. Faubel S. Heissler 《The European physical journal. Special topics》2008,153(1):41-44
Photothermal deflection spectroscopy was applied for
selective detection of the intensely coloured iron(II) chelate with
ferrozine on Silufol plates. The linearity range was 1×10-11 - 6×10-8 mol cm-2
of chelate at the plate surface, which corresponded to 1×10-9 - 4×10-6 M of chelate in
solution. The limits of detection and quantification are 8×10-12 and 20×10-12 mol cm-2
at the plate from 15 μL of test solution (0.5 nM and 1.5 nM in
solution, respectively), which corresponded to n ×10-18 mol absolute amounts of the chelate at the detection
zone. 相似文献