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1.
A nonincremental interferometer for the absolute measurement of distances is presented. The measuring technique is based on both dispersive white-light (DWL) interferometry and frequency-modulated continuous-wave (FMCW) interferometry. The proposed configuration integrates both techniques in the same interferometer by use of a single laser diode. This solution enables the results from the coarse measurements from the FMCW interferometer to be combined with the fine readouts from the DWL interferometer. Preliminary experimental results confirm the capability of the system to combine the advantages of the two techniques. 相似文献
2.
Polarization spectroscopy in the mid-infrared (IRPS) has been applied to the detection of acetylene molecules making use of the asymmetric C-H stretching vibration at around 3 μm. The infrared laser pulses were produced through difference frequency generation in a LiNbO3 crystal pumped by a Nd:YAG and dye laser system. By directly probing the ro-vibrational transitions with IRPS, sensitive detection of molecules with otherwise inaccessible electronic states was realized with high temporal and spatial resolution by using a pulsed laser and a cross-beam geometry. Detection sensitivities of 2 × 1013 molecules/cm3 (10 ppm in 70 mbar gas mixture) of C2H2 were achieved using the P(1 1) line of the (0 1 0(1 1)0)-(0 0 0 00 00) band. The dependence of the IRPS signal on the pump laser fluence, acetylene mole fraction, and buffer gas pressure of Ar, N2, H2, and CO2 has been studied experimentally. The investigation demonstrates the quantitative nature of IRPS for sensitive detection of polyatomic IR active molecules. In order to fully demonstrate the technique for combustion applications, nascent acetylene molecules were measured in a low pressure methane/oxygen flame. 相似文献
3.
Three types of lasers (double-heterostructure 66 K InAsSb/InAsSbP laser diode, room temperature, multi quantum wells with
distributed feedback (MQW with DFB) (GaInAsSb/AlGaAsSb based) diode laser and vertical cavity surface emitting lasers (VCSELs)
(GaSb based) have been characterized using Fourier transform emission spectroscopy and compared. The photoacoustic technique
was employed to determine the detection limit of formaldehyde (less than 1 ppmV) for the strongest absorption line of the
v3 + v5 band in the emission region of the GaInAsSb/AlGaAsSb diode laser. The detection limit (less than 10 ppbV) of formaldehyde
was achieved in the 2820 cm−1 spectral range in case of InAsSb/InAsSbP laser (fundamental bands of v1, v5). Laser sensitive detection (laser absorption together with high resolution Fourier transform infrared technique including
direct laser linewidth measurement, infrared photoacoustic detection of neutral molecules (methane, form-aldehyde) is discussed. 相似文献
4.
A technique of detection of ozone, using a CO2 laser with rapid automated tuning over 8–10 generation lines in the 9.4–9.6-µm spectral range, has been developed. Its experimental verification has shown a higher accuracy of detecting low concentrations of O3 in comparison with the traditional technique of differential absorption on two lines (on-line and off-line). Using the technique suggested, the content of ozone in the vicinity of city roads with heavy traffic has been measured.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 2, pp. 251–255, March–April, 2005. 相似文献
5.
新近研制的车载式双波长米散射激光雷达可用于1 064 nm 和532 nm两个波长对白天与夜晚对流层气溶胶消光系数垂直分布进行的探测。该激光雷达由激光发射单元、接收光学和后继光学单元、信号探测和采集单元以及系统运行控制单元组成,后继光路之间采用光纤导光、高低层分层探测等关键技术。该激光雷达使用1 064 nm和532 nm的两个波长,其单发脉冲能量分别为400和300 mJ,重复频率都为20 Hz,光束发散角小于0.5 mrad ;望远镜接收视场为1~3 mrad,滤光片的中心波长为1 064 nm和532 nm,带宽1 nm。分别使用R3236及H7680的PMT和VT120及Phillips777的放大器对两个波长的信号进行探测;对532 nm波长用3 A/D采集卡、1 064 nm波长用了光子计数卡。给出了双波长测量对流层气溶胶消光系数垂直分布的结果,该激光雷达可以探测10
-5~1之间的消光系数,探测高度可达10 km以上。 相似文献
6.
Active remote sensing is a promising technique to close the gaps that exist in global measurement of atmospheric carbon dioxide
sources, sinks and fluxes. Several approaches are currently under development. Here, an experimental setup of an integrated
path differential absorption lidar (IPDA) is presented, operating at 1.57 μm using direct detection. An injection seeded KTP-OPO
system pumped by a Nd:YAG laser serves as the transmitter. The seed laser is actively stabilized by means of a CO2 reference cell. The line-narrowed OPO radiation yields a high spectral purity, which is measured by means of a long path
absorption cell. First measurements of diurnal variations of the atmospheric CO2 mixing ratio using a topographic target were performed and show good agreement compared to simultaneously taken measurements
of an in situ device. A further result is that the required power reference measurement of each laser pulse in combination
with the spatial beam quality is a critical point of this method. The system described can serve as a testbed for further
investigations of special features of the IPDA technique.
PACS 42.65.Yj; 42.68.Wt; 92.60.hg 相似文献
7.
R. M. Lees Zhen-Dong Sun Li-Hong Xu 《International Journal of Infrared and Millimeter Waves》2008,29(2):148-156
Reported far-infrared laser lines for five different transition systems of CH3NH2 optically pumped by a CO2 laser have been identified spectroscopically through a high-resolution Fourier transform infrared study of the C-N stretching
band together with CO2-laser/microwave-sideband broad-scan and Lamb-dip measurements. From the infrared analysis plus previous far-infrared (FIR)
results for the ground vibrational state, quantum numbers have been assigned for seven methylamine FIR laser transitions and
their C-N stretching pump absorptions coincident with the CO2 laser lines. The assignments are confirmed through the use of closed frequency combination loops that also provide improved
FIR laser frequencies to spectroscopic accuracy. 相似文献
8.
Zirconium dioxide (ZrO2) thin films were deposited on BK7 glass substrates by the electron beam evaporation method. A continuous wave CO2 laser was used to anneal the ZrO2 thin films to investigate whether beneficial changes could be produced. After annealing at different laser scanning speeds by CO2 laser, weak absorption of the coatings was measured by the surface thermal lensing (STL) technique, and then laser-induced damage threshold (LIDT) was also determined. It was found that the weak absorption decreased first, while the laser scanning speed is below some value, then increased. The LIDT of the ZrO2 coatings decreased greatly when the laser scanning speeds were below some value. A Nomarski microscope was employed to map the damage morphology, and it was found that the damage behavior was defect-initiated both for annealed and as-deposited samples. The influences of post-deposition CO2 laser annealing on the structural and mechanical properties of the films have also been investigated by X-ray diffraction and ZYGO interferometer. It was found that the microstructure of the ZrO2 films did not change. The residual stress in ZrO2 films showed a tendency from tensile to compressive after CO2 laser annealing, and the variation quantity of the residual stress increased with decreasing laser scanning speed. The residual stress may be mitigated to some extent at proper treatment parameters. 相似文献
9.
Koo Hendrik Kurniawan 《应用光谱学评论》2013,48(2):99-130
Abstract Hydrogen emission in laser plasma has been studied by focusing a TEA CO2 laser and Nd‐YAG lasers on various types of samples, such as glass, quartz, and zircaloy pipes doped with hydrogen. It was found that Hα emission with a narrow spectral width occurs with high efficiency when the laser plasma is produced in low‐pressure host gas. In contrast, the conventional well‐known laser‐induced breakdown spectroscopy (LIBS), which operates at atmospheric air pressure, cannot be applied for the analysis of hydrogen as impurity. The specific characteristic of hydrogen emission in low‐pressure plasma is interpreted on the basis of our shock wave model, taking account of the fact that the hydrogen mass is extremely light compared to that of the host target. Another experimental study on gas analysis was conducted using an Nd‐YAG laser and helium host gas at atmospheric pressure on a sample of mixed water (H2O) and heavy water (D2O) in vapor form. It was shown that completely resolved hydrogen (Hα) and deuterium (Dα) emission lines that are separated by only 0.179 nm could be obtained at a properly delayed detection time when the charged particles responsible for the strong Stark broadening effect in the plasma have mostly disappeared. It is argued that a helium metastable excited state plays the important role in the hydrogen excitation process. 相似文献
10.
The optical nonlinearities of Cu(mpo)2 [formula = C10H8N2CuO2S2] complex have firstly been investigated by using the Z-scan technique with a nanosecond-pulsed Nd:YAG laser at its second harmonic (532 nm) radiation. The nonlinear optical absorption and refraction coefficients of Cu(mpo)2 have been measured with the different on-axial peak irradiances I
0 at the waist ranging from 0.48 to 5.66 GW/cm2. The nonlinear transmittance characteristics exhibit the near resonant two-photon absorption (TPA) at 532 nm and are explained by a population redistribution model. The nonlinear absorption originates from the near resonant TPA while the mechanism of the nonlinear refraction is the near resonant TPA transition enhancement. The linear increasing dependences of the optical nonlinearities on the incident irradiance arise from the population redistribution due to the near resonant TPA. 相似文献
11.
K. Sasaki O. Takahashi N. Takada M. Nagatsu T. Tsukishima T. Okada S. Okajima Y. Tsunawaki S. Sudo K. N. Sato et al. 《International Journal of Infrared and Millimeter Waves》1995,16(12):2133-2146
Spectrally narrow, pulsed outputs consisting of almost a single mode have been obtained from an optically-pumped high-power (200kW) D2O laser by adopting the injection seeding method, where single-mode radiation (seed pulse) from a low-power, compact D2O laser has been injected into the main D2O laser. Spectrally narrow outputs with high power having spectral widths as narrow as 5 MHz have been obtained, when the seed pulses with frequency tuned to one longitudinal mode of the main D2O laser have been injected at a time sufficiently before the lasing of the main laser took place. The experimental results have been compared with those of numerical simulation modified to include the injection field with varying injection times. 相似文献
12.
Application of a characterized difference-frequency laser source to carbon monoxide trace detection 下载免费PDF全文
Alireza Khorsandi Zahra Shabani Monireh Ranjbar S. Ali Hoseinzadeh Salati 《中国物理 B》2012,21(6):64213-064213
A tunable continuous wave(cw) mid-infrared(MIR) laser based on difference-frequency generation(DFG) in a 1.5-cm long AgGaS2 nonlinear crystal for trace gas detection is reported.Two visible and near-infrared diode lasers were used as pump and signal sources.The MIR-DFG laser was tunable in a wavelength range of 4.75 μm-4.88 μm.The phase-matching(PM) condition was non-critically achieved by adjusting the temperature of the crystal for fixed pairs of input pump and signal wavelengths.The required PM temperatures of the generated MIR-DFG wavelengths have been calculated by using three sets of recent Sellmeier equations and the temperature-dispersion equations of AgGaS2 given by Willer U,et al.(Willer U,Blanke T and Schade W 2001 Appl.Opt.40 5439).Then the calculated PM temperatures are compared with the experimental values.The performance of the MIR-DFG laser is shown by the trace detection of the P(16) carbon monoxide(12C16O) absorption line in a laboratory-fabricated absorption cell.The enhanced sensitivity of about 0.6×10 4 was obtained through the long path absorption provided by consecutive reflections between coated cylindrical mirrors of a constructed cell. 相似文献
13.
利用固相反应法制备Pr0.5Ca0.5MnO3(PCMO)靶材,并采用脉冲激光沉积法(PLD)在n型Si(111)基片上沉积PCMO外延薄膜,研究了薄膜的输运特性及薄膜与Si衬底形成异质结的整流特性.结果表明:在80—300 K温度范围内,PCMO薄膜的阻温关系符合变程跳跃模型,随着温度的升高表现出从一维到二维再到三维的转变,分析认为可能源于轨道自由度对电子输运特性的影响.PCMO/Si异质结在磁场作用下整流特性得到改善,且在正向电流方向出
关键词:
0.5Ca0.5MnO3')" href="#">Pr0.5Ca0.5MnO3
Si
整流
正磁电阻 相似文献
14.
Tianli Feng Shengzhi Zhao Kejian Yang Guiqiu Li Dechun Li Jia Zhao Bin Zhao Yonggang Wang 《Optik》2014
By using mixed crystal Nd:Lu0.15Y0.85VO4 as laser medium, KTP as frequency-doubling crystal, a diode-pumped intracavity-frequency-doubled Q-switched and mode-locked (QML) Nd:Lu0.15Y0.85VO4/KTP green laser with acousto-optic (AO) modulator and central semiconductor saturable absorption mirror (C-SESAM) is realized by using a V-type cavity. The QML laser characteristics such as the pulse width, single-pulse energy, have been measured for different modulation frequencies of the AO modulator. In comparison with the singly passively QML green laser with central SESAM, the doubly QML green laser can generate more stable and shorter pulses with higher peak power. Based on the coupled rate equations for a diode-pumped doubly QML green laser with AO and C-SESAM, in which the saturated absorption mechanism of C-SESAM is considered, the recurrence relation of the relative amplitude of the mode-locking pulses is given and the related numerical simulations are in good agreement with the experimental results. 相似文献
15.
A simple and sensitive technique, which utilizes the sensing of both the discharge current and the visible light emission from the discharge, has been developed to detect the arc formation during the operation of a high repetition rate TEA CO2 laser. It is shown that the optical detection in the visible spectral region is more sensitive than that it is in the UV region and hence can be used more effectively to monitor the onset of arc formation, while the current signal is useful in the strong arc formation regime. We demonstrate that the trigger signals generated by both the methods can be employed for reliable protection of the laser system from catastrophic damage due to deleterious arc formation. 相似文献
16.
M. Ingusio A. Moretti G. Moruzzi F. Strumia 《International Journal of Infrared and Millimeter Waves》1981,2(5):943-986
An extensive theoretical and experimental analysis of the absorption and emission spectrum of a CH3OH FIR-laser excited by a conventional CO2 laser is presented. Particular interest is devoted to the Stark shifts of the pump and lasing lines and to the electric field dependence of the Fir-laser output of the various lines. The offsets with respect to the exciting radiation and the Stark shifts of the IR absorption (pump) lines are measured by means of the transferred Lamb dip technique. The theoretical behaviours of the Stark patterns are calculated for several choices of the quantum numbers and selection rules involved in the transitions. A large variety of experimental results are reported and compared to theory. Non-linear Stark shifts have been observed for the 37.5m FIR laser line and for the IR-pump transitions excited by the 9-P(38) and 10-R(38) CO2 laser Lines. Line assignments are proposed and new FIR laser lines are reported. 相似文献
17.
V. Stasi G. Cattaneo S. Franz M. Bestetti M.C. Ubaldi D. Piccinin S.M. Pietralunga 《Photonics and Nanostructures》2007,5(2-3):136-139
A pre-patterning method of aluminium surface, in order to obtain highly ordered nanoporous anodized alumina on large areas is presented. Aluminium single crystals have been used as a substrate and a 2D hexagonally closed-packed lattice of shallow pits, with diameter of about 200 nm and period of 350 nm, has been successfully achieved by direct writing laser lithography (DWL) and wet etching. Finally, anodic oxidation of the single crystal at high cell voltage in phosphoric solution results in oxide growth with pore ordering superimposed by the pre-patterning procedure. 相似文献
18.
E. C. C. Vasconcellos S. C. Zerbetto L.-H. Xu R. M. Lees L. R. Zink K. M. Evenson 《International Journal of Infrared and Millimeter Waves》1998,19(5):719-726
Eight far-infrared laser lines have been obtained by optically pumping acetaldehyde (CH3CHO) and nine by pumping vinyl fluoride (CH2CHF) with a cw CO2 laser. The far-infrared laser structure used a metal-dielectric waveguide cavity. This is the first reported observation of four of the laser lines in acetaldehyde. In this work, we measure the frequency, optimum pressure of operation, relative intensity, relative polarization, and pump offset from CO2 laser-line center. 相似文献
19.
We have recorded electronic spectra of some diatomic species (I2, K2, and NaK), to illustrate the potential power of the combination of two high resolution techniques: intra-cavity laser induced fluorescence (ICLIF) and Fourier transform (FT) spectroscopy. Active and passive optical cavities have been used, working with visible continuous wave (cw) laser sources. The active cavity is a modified commercial ring dye laser, allowing for a sample up to 25 cm in length. Dispersed fluorescence spectra recorded on a Bomem Fourier transform spectrometer showed a signal enhancement of about 10 when a molecular source was placed within the resonator. The system was tested with a heatpipe source, producing alkali metal vapour at about 300 °C. These experiments illustrate enhanced cascade excitation mechanisms in K2; the highest vibrational levels of the electronic ground state of K2 can be observed with surprising ease. The increase in available power within the cavity has also led to the observation of fluorescence in NaK excited by a two-photon transition (Q (66) 61Σ+ ← X1Σ+ transition). Spatial limitations have driven us to build a more versatile ring cavity able to accommodate larger sources. This broad-band (590-650 nm) build-up cavity is locked by a Hänsch-Couillaud servo-loop to an input laser of (instantaneous) bandwidth ∼1 MHz. Power enhancement factors of around 30 have been obtained with a 2.6% input coupler. The performance of the build-up cavity has been tested by recording FT spectra of intra-cavity laser induced fluorescence of iodine. The technique clearly has useful applications for weakly absorbing species, or for those whose electronic states are inaccessible to single-photon absorption techniques. This paper describes the arrangement we have used, highlighting some of the advantages and describing some of the particular difficulties we have encountered. 相似文献
20.
A. De Michele K. Bousbahi G. Carelli A. Moretti 《International Journal of Infrared and Millimeter Waves》2003,24(10):1649-1654
We have investigated CHD2OH methanol as source of far-infrared (FIR) laser radiation using the optical pumping technique. Our new waveguide pulsed CO2 laser, with peak powers as high as some kW, has allowed us to observe 12 new lines. Each of them is characterized in wavelength, relative polarization, intensity, optimum operating pressure and pump offset from the center of the exciting CO2 line. 相似文献