共查询到20条相似文献,搜索用时 15 毫秒
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噪声免疫腔增强光外差分子光谱技术(NICE-OHMS)由于结合了频率调制光谱与腔增强光谱两种技术,不仅可以将激光耦合到高精细度谐振腔大幅提高腔内功率,还可以实现低气压样品气体的高灵敏测量,因此基于该技术可以实现分子吸收线的饱和,获得亚多普勒光谱,从而能作为激光频率锁定的参考.本文基于光纤激光器的NICE-OHMS技术,将光纤激光器频率锁定到NH3的亚多普勒吸收线上.首先分析了基于Pound-Drever-Hall和DeVoe-Brewer技术实现激光到腔模和调制频率到腔自由光谱区频率锁定的性能,之后在腔内气压为70 mTorr条件下,测量了半高全宽为2.05 MHz的NH3亚多普勒信号,最后将1.53μm的光纤激光器频率锁定到该亚多普勒吸收线上,相对频率偏差为16.3 kHz,阿伦方差结果显示,136 s积分时间下频率稳定度达到1.6×10~(-12). 相似文献
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A combination of optical feedback self-locking of a continuous-wave distributed feedback diode laser to a V-shaped high finesse cavity, laser phase modulation at a frequency equal to the free spectral range of the V-cavity and detection of the transmitted laser beam at this high modulation frequency is described for the possible application in cavity-enhanced absorption spectroscopy. In order to estimate the noise level of an absorbance baseline, the triplet of frequency modulated light, i.e. the central laser frequency and the two sidebands, were transmitted through both the V-cavity in open air and a 1.5-cm long optical cell placed behind the cavity output mirror and filled with acetylene (C2H2) at low pressure. The performance of the setup was evaluated from the measured relative intensity noise on the cavity output (normalised by the bandwidth) and the frequency modulation absorption signals induced by C2H2 absorption in the 1.5-cm cell. From these data, we estimate that the noise-equivalent absorption sensitivity of 2.1 × 10?11 cm?1 Hz?1/2—by a factor of 11.7 above the shot-noise limit—can be achieved for C2H2 absorption spectra extracted from the heterodyne beat signals recorded at the transmission maxima intensity peaks of the successive TEM00 resonances. 相似文献
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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
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A.A. Feinberg 《Optics Communications》1984,51(6):438-440
A simple spectroscopic technique is used to detect low-frequency acoustical phonons. Resonantly enhanced modulated transfer processes in optical heterodyne spectroscopy are accomplished from a frequency shifted modulated beam to an unmodulated beam in a nonlinear medium having low-frequency induced phonons. The resonance condition is achieved when the phonon frequency is set equal to the beat frequency of the two beams. 相似文献
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Diffuse optical tomography (DOT) is one of the emerging modalities for the non-invasive imaging of thick biological tissues using near-infrared (NIR) light. This article reviews the fundamentals and development of DOT technology since its advent in the early 1990s, including the modeling of light propagation in biological tissues which strongly scatter and weakly absorb NIR light, the optical properties of biological tissues in the NIR wavelength range, three typical measurement methods, image reconstruction algorithms, and so forth. Then various studies are referred to for improvement of the DOT images, which are essentially low in quality due to the ill-conditioned and underdetermined problem. Studies and clinical applications presently attracting much attention are discussed in some detail. Finally, the expected future developments are summarized. 相似文献
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I. Courtillot J. Morville V. Motto-Ros D. Romanini 《Applied physics. B, Lasers and optics》2006,85(2-3):407-412
We report preliminary results on the first application of optical feedback cavity-enhanced absorption spectroscopy with a blue (411 nm) extended cavity diode laser (ECDL) for NO2 detection. While this technique was originally developed to operate with distributed feedback diode lasers in the near infrared, it is here extended to ECDLs and applied to the blue spectral region. With a simple and compact optical setup, we demonstrate from the baseline noise a minimum detectable NO2 concentration of 6×109 molecules/cm3 for a single laser scan (70 ms), which extrapolated under atmospheric conditions corresponds to 200 pptv. Signal averaging should allow further lowering of this limit. Observed absorption spectra display more structure than previous spectra obtained at lower resolution by Fourier-transform spectroscopy at the same wavelength. PACS 07.88.+y; 42.55.Px; 42.62.Fi 相似文献
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The noise characteristic of available laser sources limits the sensitivity of many types of nonlinear spectroscopy. We show
how to maximize the sensitivity by optimizing the strength of a local oscillator wave in a heterodyne detection scheme without
altering the amplitude of the wave being detected. The intensity profile of the optimum local oscillator closely matches that
of the incident probe wave, but the optimum intensity is much less than that of the probe under realistic conditions. A general
signal-to-noise analysis applicable to all nonlinear spectroscopy techniques is presented along with specific applications
to coherent Raman spectroscopy, two-photon absorption, saturation spectroscopy, and optical coherent transient techniques.
A simple optimization procedure employing polarization selection rules is described. Detailed calculations are performed for
the case of TEM00 waves interacting via a third-order nonlinear susceptibility and for the case where the sample is simultaneously probed at
many different frequency combinations.
Supported by the National Science Foundation and Office of Naval Research. 相似文献
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Zee Hwan Kim 《Frontiers of Physics》2014,9(1):25-30
The single-molecule surface-enhanced Raman scattering (smSERS) has been extensively studied after the initial observation in 1997, yet there still exist unsettled issues in the fundamental mechanism of smSERS. In this review, we survey some of the recent breakthroughs in the mechanism of smSERS and its application. 相似文献
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《Radiation measurements》2007,42(4-5):576-581
Studies and applications of thermoluminescence (TL) dosimetric materials are reviewed. It is shown that the properties of commercial TL dosimeters satisfy a set of stringent requirements. The search and development of storage materials with required TL properties is based on approaches that involve the evaluation of the luminescence light yield. The specific features required for the dosimetry of high-energy particles and fast and thermal neutrons are considered. The use of TL with deep traps in high-temperature dosimetry is discussed. Results of pioneering studies of TL in nanosized materials are briefly presented. 相似文献
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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
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Stark modulation of vibration-rotational absorption resonances in five asymmetric rotor molecules with hindered internal rotation allows selective detection of trace organic gas concentrations in air by means of phase fluctuation optical heterodyne spectroscopy. A parallel-beam interferometric configuration is described. 相似文献
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A compact high-resolution optical heterodyne interferometer combining a two-frequency light module and a minute optical system
is described. The light module, which generates two independent frequencies of light, is fabricated by proton exchange method
on LiNbO3 substrate. We report an experiment evaluating measurement accuracy using a micro-displacement measurement system which incorporates
this interferometer. Results of the experiment with a standard thickness sample show high thermal stability with maximum measurement
error of 1.8 nm at a temperature from 19°C to 33°C. The system was used to measure the hysteresis of a piezoelectric element
for displacements of several nm, thereby making it possible to analyze the system quantitatively in practice. 相似文献
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Laser linewidth affects baseline mode structured variations and hence measurement absorption sensitivity in off-axis cavity enhanced absorption spectroscopy with a continuous-wave tunable laser and a stable optical cavity formed by two high reflectivity mirrors. Cavity transmittances have been calculated for various laser linewidths and different optical beam re-entrant conditions for the cavity when overlapping of the optical beams occurs on the cavity mirrors after a finite number of beam round trips within the cavity. It is shown that in order to achieve maximum absorption sensitivity both a specific laser linewidth and specific arrangement of the optical cavity have to be selected and defined using the proposed approach. 相似文献
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Fourier-transform heterodyne spectroscopy is a simple but powerful technique to study narrow line shapes and small frequency
shifts. We review the technique and its application to the study of hydrodynamic fluctuations. We introduce a simple scheme
for obtaining the full spectrum of light scattered from liquid and solid surfaces. Using this scheme we obtained a spectral
resolution of 200 Hz. Two applications of the technique, one involving the detection of counter-propagating capillary waves, the other measurement
of the epitaxial crystal-growth speed of a crystalline silicon interface, are presented.
Received: 21 August 1996 相似文献