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1.
Near- and mid-infrared laser-optical sensors for gas analysis 总被引:3,自引:0,他引:3
Peter Werle Franz Slemr Karl Maurer Robert Kormann Robert Mücke Bernd Jnker 《Optics and Lasers in Engineering》2002,37(2-3)
Semiconductor diode lasers were first developed in the mid-1960s and found immediate application as much needed tunable sources for high-resolution laser spectroscopy commonly referred to as tunable diode laser absorption spectroscopy (TDLAS). In this paper, currently available semiconductor lasers for spectroscopy in the near- and mid-infrared spectral region based upon gallium arsenide, indium phosphite, antimonides and lead-salt containing compounds will be reviewed together with the main features of TDLAS. Room-temperature measurements of atmospheric carbon dioxide near 2 μm will be discussed and recent results obtained with a fast chemical sensor for methane flux measurements based on lead-salt diode lasers operating near 7.8 μm will be presented. 相似文献
2.
Experimental techniques have been developed to monitor transient infrared absorptions using lead-salt tunable diode lasers. The techniques are easily implemented, yield sensitivities which are limited by detector noise at 10–5 level of absorbance, and have a response time on the order of one microsecond. The transient absorption detection techniques are high frequency versions of the sweep integration technique pioneered by Jennings [Appl. Opt.19, 2695 (1980)]. TDL modulation rates of 100 kHz and 500 kHz allow for absorption sampling rates of 200 kHz and 1 MHz, respectively. In order to reproducibly achieve near-detector-noise-limited sensitivities for 100 kHz TDL modulation rates, an automated analog subtraction circuit has been developed which removes the effects of minor TDL power variations. At the 500 kHz modulation rate, digital filtering techniques are used to remove the effects of this power variation. 相似文献
3.
R. Brüggemann M. Petri H. Fischer D. Mauer D. Reinert W. Urban 《Applied physics. B, Lasers and optics》1989,48(2):105-110
A computer-controlled diode laser spectrometer for the 1200 to 2500 cm–1 spectral region is described. The spectrometer has been applied to high resolution spectroscopy of the NCO radical at 5.2 m. The lead-salt diode lasers are cooled to their operating temperature with a temperature adjustable helium evaporation cryostat. Computer-controlled tuning procedures for the frequency tuning of the diode lasers have been developed; they are independent of tables describing the tuning characteristics of the diode lasers. 41 lines of the antisymmetric stretching-vibrationv
3 of the linear NCO radical have been observed. We were able to detect vibration-rotation transitions in both2
1/2 and2
3/2 fine structure sublevels. These measurements led to the precise determination of additional molecular constants. 相似文献
4.
The minimum absorption detectable by a tunable diode laser spectrometer utilising harmonic techniques is often limited by interference fringes generated by scattered light. The sensitivity of the spectrometer to absorption can be increased by applying a jitter modulation. In this paper, the theory of harmonic response for single- and two-tone modulation over optical fringes and Lorentzian absorption lines is developed and compared to experimental measurements. A simple analytic expression for the two-tone harmonic line shape is derived. This expression provides a physical understanding of the effects of the second modulation, and a means to unravel the effects of the second modulation on the linewidth and line shape. For a specific choice of the jitter frequency and phase, it is possible to simultaneously minimise the fringe signal and increase the harmonic absorption signal. The results of this investigation are applicable to trace gas detection using tunable diode lasers, and to other areas of spectroscopy and magnetic resonance where harmonic techniques are used.This work was supported by the Natural Sciences and Engineering Research Council of Canada, and the Ontario Ministry of the Environment 相似文献
5.
N. Strauß I. Ernsting S. Schiller A. Wicht P. Huke R.-H. Rinkleff 《Applied physics. B, Lasers and optics》2007,88(1):21-28
We present a simple scheme for tuneable relative frequency stabilization of lasers. A highly sensitive and accurate frequency-to-voltage
converter is used to derive an error signal from the beat note between two lasers. We analyze in detail detector noise and
drift, modulation detection bandwidth, and cross-talk from power modulation. The results indicate that sub-kHz relative linewidth
and a locking point drift on the order of 100 Hz for times scales of 1 h are achievable. The scheme can, therefore, be applied
to situations where up to now only optical PLLs could provide sufficient accuracy and precision. To demonstrate its potential
for high-resolution, high-precision spectroscopy we lock a diode laser to a fs-frequency comb and find a relative linear drift
of 314 Hz during a 2.8 h period.
PACS 42.62.Fi; 42.62.Eh 相似文献
6.
B. Sumpf T. Kelz M. Nägele H.-D. Kronfeldt 《Applied physics. B, Lasers and optics》1997,64(5):521-524
2 and two diode lasers as pump sources and experiments with this setup are presented. In contrast to the majority of known
applications of the difference frequency mixing with solid state or gas lasers, we apply two single mode diode lasers with
emission wavelengths of 690 nm and 805 nm, respectively. By fixing the emission wavelength of one diode laser and tuning the
wavelength of the second laser, by changing temperature or excitation current, we can cover typically 0.87 cm-1 (FWHM) in good agreement with recently published data and theory. With an input power of 20 mW and 6 mW we achieved an output
power in the nW-range. To demonstrate the capabilities of the spectrometer we scanned CO and OCS absorption lines near 2107 cm-1. From these experiments we deduce an overall signal-to-noise ratio of 1000:1 and a spectral resolution better than 30 MHz.
With such parameters a trace gas detection of CO at sub-ppm level will be possible.
Received: 19 August 1996/Revised version: 5 November 1996 相似文献
7.
E. D. McNaghten K. A. Grant A. M. Parkes P. A. Martin 《Applied physics. B, Lasers and optics》2012,107(3):861-871
We report what we believe to be a novel demonstration of simultaneous detection of multiple trace gases by near-IR tunable diode laser photoacoustic spectroscopy using a cell containing a cantilever microphone. Simultaneous detection of carbon monoxide (CO), ethyne (C2H2), methane (CH4) and combined carbon monoxide/carbon dioxide (CO+CO2) in nitrogen-based gas mixtures was achieved by modulation frequency division multiplexing the outputs of four near-IR tunable diode lasers. Normalized noise-equivalent absorption coefficients of 3.4×10?9, 3.6×10?9 and 1.4×10?9 cm?1?W?Hz?1/2 were obtained for the simultaneous detection of CO, C2H2 and CH4 at atmospheric pressure. These corresponded to noise-equivalent detection limits of 249.6 ppmv (CO), 1.5 ppmv (C2H2) and 293.7 ppmv (CH4) respectively over a measurement period of 2.6 s at the relevant laser power. The performance of the system was not influenced by the number of lasers deployed, the main source of noise arising from ambient acoustic effects. The results confirm that small-volume photoacoustic cells can be used with low optical power tunable diode lasers for rapid simultaneous detection of trace gases with high sensitivity and specificity. 相似文献
8.
M. Schmidt M. Prevedelli A. Giorgini G. M. Tino A. Peters 《Applied physics. B, Lasers and optics》2011,102(1):11-18
We present a modular rack-mounted laser system for the cooling and manipulation of neutral rubidium atoms which has been developed
for a portable gravimeter based on atom interferometry that will be capable of performing high-precision gravity measurements
directly at sites of geophysical interest. This laser system is constructed in a compact and mobile design so that it can
be transported to different locations, yet it still offers improvements over many conventional laboratory-based laser systems.
Our system is contained in a standard 19″ rack and emits light at five different frequencies simultaneously on up to 12 fibre
ports at a total output power of 800 mW. These frequencies can be changed and switched between ports in less than a microsecond.
The setup includes two phase-locked diode lasers with a phase noise spectral density of less than 1 μrad/Hz1/2 in the frequency range in which our gravimeter is most sensitive to noise. We characterise this laser system and evaluate
the performance limits it imposes on an interferometer. 相似文献
9.
《应用光谱学评论》2013,48(4):395-432
Abstract The need for higher sensitive detection technology for trace gas samples, either in the laboratory setup or in the atmospheric remote sensing has been a goal for several decades. The development of the tunable diode laser has propelled the progress of trace detection technology, and modulation technology enables the improvement of the detection sensitivity. As a result, the detection of 10?7 or 10?8 absorbance is possible for some applications, and modulation technology has been applied to the ultraviolet as well as mid-infra red wavelength range. In this review, recent progress of tunable diode lasers and diode laser-based modulation technologies are presented. Wavelength modulation, frequency modulation, and two-tone frequency modulation techniques are mainly described along with the actual application of the techniques. In addition, the state-of-the-art of diode laser development which can be adopted for the trace detection is presented. 相似文献
10.
Diode laser spectroscopy of overtone bands of acetylene 总被引:1,自引:0,他引:1
A. Lucchesini M. De Rosa D. Pelliccia A. Ciucci C. Gabbanini S. Gozzini 《Applied physics. B, Lasers and optics》1996,63(3):277-282
Overtone absorption lines of acetylene in the regions around 12700 and 11800 cm–1 have been examined by the use of tunable diode lasers in free-running mode. The diode laser emission wavelength was scanned around the gas resonances by simply sweeping its injection current, permitting a direct observation of the absorption line-shapes. Weak overtone absorption lines have been detected by using the wavelength modulation (WM) spectroscopy with 2nd harmonic detection technique and the collisional broadening and shift coefficients have been obtained. The high resolving power and accuracy of the spectrometer permitted a wavenumber error of less than 0.01 cm–1. The correct interpretation of the absorption signals when detecting the second harmonic in the presence of a sloping background is discussed. 相似文献
11.
T. Caniard T. Briant P. -F. Cohadon M. Pinard A. Heidmann 《Optics and Spectroscopy》2007,103(2):225-230
We have developed an experiment of ultrasensitive interferometric measurement of small displacements based on a high-finesse
Fabry-Perot cavity. We have observed the internal thermal noise of mirrors and fully characterized their acoustics modes with
a sensitivity of 3 × 10−20 m/Hz1/2. This unique sensitivity is a step towards the first observation of the radiation pressure effects and the resulting standard
quantum limit in interferometric measurements. Our experiment may become a powerful facility to test quantum noise reduction
schemes such as the use of squeezed light or quantum locking of mirrors. As a first result, we present the observation of
a cancellation of radiation pressure effects in our cavity. This back-action noise cancellation was first proposed within
the framework of gravitational-wave detection with dual resonators, and may drastically improve the sensitivity of such measurements.
The text was submitted by the authors in English. 相似文献
12.
The coherence length of a single mode laser diode (LD) can reach more than 10 m. It allows the application of this source of light to interferometric distance measurement, with a measurement range of several meters. However, the LD's wavelength tunability, which is a result of the dependence of the lasing wavelength on the injection current, prevents the realization of the theoretically possible metrological parameters of the interferometer. In this study, we analyze the influence of a low-frequency signal disturbance, e.g., noise or disturbing modulation inherent to the injection current of the LD, on the repeatability and measurement range of an LD interferometer used for displacement measurements. Both the measurement range and the resolution of the interferometer are found to be highly limited by this factor. 相似文献
13.
A novel method is described for fast frequency modulation or frequency control of diode lasers that avoids problems associated with bias current modulation, namely, amplitude modulation and thermal phase delays. The method is based on amplitude-modulated, noninterfering control light with a wavelength near the transparency region of the laser diode, which specifically modifies the spectral gain profile to yield a constant gain but a controllable refractive index at the lasing wavelength. This permits amplitude-modulation-free frequency modulation at modulation frequencies up to the relaxation oscillation frequency. A phase lock between the emissions of two extended-cavity diode lasers that could not be achieved with bias current modulation was achieved by this method. 相似文献
14.
A compact system for methane sensing based on the Quartz-Enhanced Photoacoustic Spectroscopy technique has been developed. This development has been taken through two versions which were based respectively on a Fabry Perot quantum wells diode laser emitting at 2.3 μm, and on a quantum wells distributed feedback diode laser emitting at 3.26 μm. These lasers emit near room temperature in the continuous wave regime. A spectrophone consisting of a quartz tuning fork and one steel microresonator was used. Second derivative wavelength modulation detection was used to perform low methane concentration measurements. The sensitivity and the linearity of the QEPAS sensor were studied. A normalized noise equivalent absorption coefficient of 7.26 × 10−6 cm−1 W/Hz1/2 was achieved. This corresponds to a detection limit of 15 ppmv for 12 s acquisition time. 相似文献
15.
Ultrasensitive absorption spectroscopy of NO2 was performed with a tunable lead-salt diode laser (TDL) using a single-tone high-frequency modulation (FM) technique. With a detection bandwidth of 200 kHz, an optical density of 2.7 × 10–5 was detectable at SNR of 1. The detectable optical density could be further improved by reducing the detection bandwidth in agreement with the f relationship, reaching 2.5 × 10–6 at a detection bandwidth of 1.56 kHz. Normalized to 1 Hz bandwidth, the demonstrated performance would then correspond to a detectable optical density of 5.9 × 10–8. This detection limit agrees well with the calculated quantum limited performance based on the measured laser power, modulation index, noise figure of the electronic components, and other parameters of the apparatus. These measurements and calculations show that by implementation of the FM technique, the sensitivity of the present TDL absorption spectrometers (TDLAS) can be improved by at least a factor of 10 and possibly even of 100. Such a sensitivity improvement would greatly extend the applicability of TDLAS for trace gas analysis, especially in atmospheric monitoring. 相似文献
16.
17.
The interferometric CD-R groove measurements in transmission and reflection mode with He–Ne and Ar+ lasers are presented. The phase micro-inhomogeneities on the surface relief of polycarbonate substrates are compared with the surface relief of a stamping onto copper layer metal master for rainbow holograms, used as a test object. The grid density of the test object is about 60% higher than the density of the CD-R groove at a similar relief depth. The reason for the phase inhomogeneities is due to the refractive index variations of the polymer substrate. The RMS of the measurements is not higher than 0.1 rad. 相似文献
18.
J. Alnis A. Matveev N. Kolachevsky T. Wilken R. Holzwarth T. W. Hänsch 《The European physical journal. Special topics》2008,163(1):89-94
We report on an external cavity diode laser at 972 nmstabilized to a mid-plane mounted Fabry-Perot (FP) resonator with afinesse
of 400000. The 0.5 Hz optical beat note line width betweentwo similar lasers (Allan deviation 2 × 10-15) is limitedby thermal noise properties of two independent FP resonators. Thelong term drift of the FP resonator and mirror
substrates made fromUltra-Low-Expansion glass (ULE) is small and can be well predictedon time intervals up to many hours if
the resonator is stabilized atthe zero thermal expansion temperature Tc. Using a Peltierelement in a vacuum chamber for temperature stabilization allowsstabilization of the FP cavity to Tc which is usually below theroom temperature. Beat note measurements with a femtosecond opticalfrequency comb referenced to
a H-maser during 15 hours have shown awell defined linear drift of the FP resonance frequency of about 60 mHz/s with residual
frequency excursions of less than ±20 Hz. 相似文献
19.
Matthew R. Abernathy Gregory M. Harry Sheila Rowan Martin M. Fejer Steve Penn Andri Gretarsson 《Physics letters. A》2008,372(2):87-90
Second-generation interferometric gravitational-wave detectors will operate at temperatures noticeably above room temperature. Study was done to determine what effect elevated temperatures would have on the Q and coating thermal noise of the detector mirrors. Results show that increased temperature increases loss angle in a manner that is more significant at higher frequencies. Trends show that the increased temperature will have a negligible effect at the low (100 Hz) frequencies important to second-generation detectors. 相似文献
20.
The modulation performance of lead-salt laser diodes suitable for mid-infrared fibre optic communication systems has been investigated. The electron and photon lifetime for a PbCdS laser have been determined to 3.1 ns and 3.3 ps, respectively. Moreover, an experiment using short lengths of fluoride fibres shows the feasibility of GHz fibre optic communication links in the mid-infrared region using lead-salt lasers if the potential ultra-low loss of mid-infrared optical fibres can be realized. 相似文献