共查询到20条相似文献,搜索用时 31 毫秒
1.
Ó. Martínez-Matos G.A. Torchia A. Lencina J.O. Tocho 《Applied physics. B, Lasers and optics》2008,91(2):363-367
Volume grating formation by spatially-selective defect bleaching is demonstrated in coloured KCl:CO3K2 crystals. The sample is coloured by a train of pulses with a wavelength of λ= 266 nm and bleached with a cw Ar-laser with
a wavelength of λ= 514.5 nm. Diffraction efficiency for a 1.6 μm grating period is studied both experimentally and theoretically,
using the evolution of colour centre concentration. Hologram recording parameters are obtained and the evolution of the spatial
grating profile is discussed. Diffraction efficiencies three times higher than previously published efficiencies are obtained.
PACS 42.40.Ht; 42.40.Lx; 42.70.Ln 相似文献
2.
C. Bauer A.K. Sharma U. Willer J. Burgmeier B. Braunschweig W. Schade S. Blaser L. Hvozdara A. Müller G. Holl 《Applied physics. B, Lasers and optics》2008,92(3):327-333
Optical methods are well-established for trace gas detection in many applications, such as industrial process control or environmental
sensing. Consequently, they gain much interest in the discussion of sensing methods for counterterrorism, e.g., the detection
of explosives. Explosives as well as their decomposition products possess strong absorption features in the mid-infrared (MIR)
spectral region between λ=5 and 11 μm. In this report we present two different laser spectroscopic approaches based on quantum
cascade lasers (QCLs) operating at wavelengths around λ=5 and 8 μm, respectively. Stand-off configuration for the remote detection
of nitro-based explosives (e.g., trinitrotoluene, TNT) and a fiber coupled sensor device for the detection of triacetone triperoxide
(TATP) are discussed.
PACS 42.62.Fi; 07.07.Df 相似文献
3.
K. Koshiba T. Honma Y. Benino T. Komatsu 《Applied Physics A: Materials Science & Processing》2007,89(4):981-986
Dots and lines consisting of nonlinear optical GdxBi1-xBO3 crystals were patterned on the surface of CuO-doped Gd2O3-Bi2O3-B2O3 glass by heat-assisted (200 °C) Nd:YAG laser irradiations with a wavelength of λ=1064 nm, where the laser energy absorbed
by Cu2+ is converted to the local heating of the surrounding Cu2+. The surface morphology and orientation of crystals in the patterned lines were clarified from confocal scanning laser microscope
observations and polarized micro-Raman scattering spectra. Crystal lines with periodic bumps (i.e., ladder-shape like lines)
were patterned by laser irradiations with a power of 0.79 W and a scanning speed of 60 μm/s, and the orientation of GdxBi1-xBO3 crystals in the lines was proposed. The present study demonstrates that the combination of Cu2+ and continuous wave Nd:YAG laser with λ=1064 nm is effective in inducting crystallization of oxide glasses. The mechanism
of laser-induced crystallization in glass has also been discussed.
PACS 61.43.Fs; 42.70.Mp; 68.35.Bs; 78.30.-j; 79.20.Ds 相似文献
4.
The effect of temperature on the spectral luminescence characteristics of PbWO4:Tb3+ crystals with synchrotron and laser excitation is studied. If PbWO4:Tb3+ is excited by synchrotron radiation with λ = 88 nm at 300 K, a faint recombination luminescence of the impurity terbium is
observed against the matrix luminescence. When the temperature is reduced to 8 K, the luminescence intensity of PbWO4:Tb3+ increases by roughly an order of magnitude and the characteristic luminescence of the unactivated crystal is observed. Excitation
of PbWO4:Tb3+ by a nitrogen laser at 300 K leads to the appearance of emission from Tb3+ ions. At 90 K, a faint matrix luminescence is observed in addition to the activator emission. The formation of the luminescence
excitation spectra for wavelengths of 60–320 nm is analyzed and the nature of the emission bands is discussed. 相似文献
5.
M. Wolff M. Germer H. G. Groninga H. Harde 《The European physical journal. Special topics》2008,153(1):409-413
We present a new detection scheme for carbon dioxide
(CO2) based on a custom-made room temperature distributed feedback
(DFB) diode laser at 2.7 μm, currently representing one of the lasers
with the highest emission wavelength of its kind. The detector's especially
compact and simple set-up is based on photoacoustic spectroscopy (PAS). This
method makes use of the transformation of absorbed modulated radiation into
a sound wave. The sensor enables a very high detection sensitivity for
CO2 in the ppb range. Furthermore, the carefully selected spectral
region as well as the narrow bandwidth and wide tunability of the
single-mode laser ensure an excellent selectivity. Even measurements of
different CO2 isotopes can be easily performed. This enables
applications in industrial sensing and medical diagnostics (e.g.
13C-breath tests). 相似文献
6.
Yan Xiong Daoqian Zhu Shiheng Chen Hong Peng Yafeng Guan 《Journal of fluorescence》2010,20(1):269-274
A novel fiber-optic evanescent wave sensor (FOEWS) for O2 detection based on [Ru(bpy)3]2+-doped hybrid fluorinated ORMOSILs (organically modified silicates) has been developed. The sensing element was fabricated
by dip-coating the optical fiber with [Ru(bpy)3]2+-doped hybrid fluorinated ORMOSILs composed of n-propyltrimethoxysilane (n-propyl-TriMOS) and 3, 3, 3-trifluoropropyltrimethoxysilane (TFP–TriMOS). Fluorophores of [Ru(bpy)3]2+ were excited by the evanescent wave field produced on the fiber core surface and the emission fluorescence was quenched by
O2. Spectroscopic properties have been characterized by FTIR and UV–VIS absorption measurements. By using the presented hybrid
fluorinated ORMOSILs, which enhances the coating surface hydrophobicity, the quenching response is increased. The sensitivity
of the sensor is 7.5, which is quantified in terms of the ratio I
N2/I
O2 (I
N2 and I
O2 represent the fluorescence intensities in pure N2 and pure O2 environments, respectively). The limit of detection (L.O.D.) is 0.01% (3σ) and the response time is about 1 s. Meanwhile,
the proposed FOEWS has the advantages of easy fabrication, low cost, fast response and suitable sensitivity for oxygen monitoring
using a cheap blue LED as light source and coupling a miniature PMT detector directly to the optical fiber probe. 相似文献
7.
K. Okazaki S. Torii T. Makimura H. Niino K. Murakami D. Nakamura A. Takahashi T. Okada 《Applied Physics A: Materials Science & Processing》2011,104(2):593-599
We investigated a simple and productive micromachining method of silica glass by ablation using a TEA CO2 laser (10.6 μm) with a spatial resolution down to sub-wavelength scale. The silica glass was irradiated by the TEA CO2 laser light through a copper grid mask with square apertures of 20×20 μm2 attached to the silica glass surface. After the irradiation, circular holes with a diameter of several μm were formed on
the silica glass surface at the centers of the apertures due to the Fresnel diffraction effect. The minimum diameter of the
holes was 3.4 μm. The characteristics of the micromachining are discussed based on the electric field distributions of the
CO2 laser light under the mask using a three-dimensional full-wave electromagnetic field simulation. 相似文献
8.
The crystal of Nd3+:Sr6YSc(BO3)6 with dimensions of O 19×42 mm3 was grown by the Czochralski method. It’s spectral and laser properties have been investigated. The absorption cross section
is 1.47×10-20 cm2 with a FWHM 12.0 nm at 807 nm, the emission cross section is 1.57×10-19 cm2 at 1060 nm, and the fluorescence lifetime is 76 μs at room temperature. The maximum laser output is 25.7 mJ at 1.06 μm pumped
by a single Xenon flash lamp and the overall and average slope efficiencies are 0.12% and 0.09%, respectively. The laser energy
threshold value is 1.28 J.
PACS 42.55.Rz; 42.70.Hj; 78.20.-e 相似文献
9.
V. M. Marchenko L. D. Iskhakova A. V. Kir’yanov V. M. Mashinsky N. M. Karatun E. M. Sholokhov 《Laser Physics》2012,22(1):177-183
Yb2O3 polycrystals with a size of up to 10 mm are synthesized using the sintering and melting of the ultrapure Yb2O3 powders by the CO2-laser radiation with the power P
L ≤ 100 W at the wavelength λ = 10.6 μm at the melting point T
m = 2703 K, forming due to surface tension in melt, and crystallization in air. The analysis of the polycrystal microstructure
using the methods of optical and electron microscopy and X- ray diffractometry shows that perfect oxide crystallites are formed
in the course of crystallization after melting-through. The transformation of the luminescence and selective heat radiation
(SHR) spectra of the Yb2O3 polycrystals is studied under the resonant excitation at λ ≈ 975 nm using a laser diode and the laser heating at the wavelength
λ = 10.6 μm. When the resonant excitation power of the Yb3+ ions increases from 0.15 to 4.5 W, the Stokes luminescence of the Yb2O3 polycrystals is sequentially transformed into SHR and the thermal radiation of the crystal lattice. The transformation of
the emission spectra of the Yb2O3 polycrystals with an increase in the laser heating intensity by about four orders of magnitude can be represented as the
low-temperature heat radiation, spectral burst of the thermodynamically nonequilibrium SHR of the Yb3+ ions, and the high-temperature radiation of the crystal lattice. The temperature dependence of the luminescence spectra and
SHR of the Yb2O3 polycrystals on the intensity of the laser and laser-thermal excitation and the concentration quenching of the Yb3+ luminescence in oxides indicate the key role of the interaction of the f-electron shell of the Yb3+ ions with the natural oscillations of the crystal lattice in the processes of the multiphonon excitation and nonradiative
(multiphonon) and radiative (vibronic) relaxation. 相似文献
10.
This paper reports on the spectroscopic properties and energy transfer analysis of Tm3+-doped BaF2-Ga2O3-GeO2-La2O3 glasses with different Tm2O3 doping concentrations (0.2, 0.5, 2.0, 2.5, 3.0, 3.5, 3.5, 4.0 wt%). Mid-IR fluorescence intensities in the range of 1,300 nm−2,200 nm
have been measured when excited under an 808 nm LD for all the samples with the same pump power. Energy level structure and
Judd-Ofelt parameters have been calculated based on the absorption spectra of Tm3+, cross-relaxation rates and multi-phonon relaxation rates have been estimated with different Tm2O3 doping concentrations. The maximum fluorescence intensity at around 1.8 μm has been obtained in Tm2O3-3 wt% sample and the maximum value of calculated stimulated emission cross-section of Tm3+ in this sample is about 0.48 × 10−20 cm2 at 1,793 nm, and there is not any crystallization peak in the DSC curve of this sample, which indicate the potential utility
of Tm3+-doped BaF2-Ga2O3-GeO2- La2O3 glass for 2.0-μm optical fiber laser. 相似文献
11.
The architecture and operation of a trace hydrogen cyanide (HCN) gas sensor based on quartz-enhanced photoacoustic spectroscopy and using a λ=1.53 μm telecommunication diode laser are described. The influence of humidity content in the analyzed gas on the sensor performance is investigated. A kinetic model describing the vibrational to translational (V–T) energy transfer following the laser excitation of a HCN molecule is developed. Based on this model and the experimental data, the V–T relaxation time of HCN was found to be (1.91±0.07)10-3 s Torr in collisions with N2 molecules and (2.1±0.2)10-6 s Torr in collisions with H2O molecules. The noise-equivalent concentration of HCN in air at normal indoor conditions was determined to be at the 155-ppbv level with a 1-s sensor time constant. PACS 82.80.Kq; 42.62.Fi 相似文献
12.
J.C. Bermudez Gutierrez M.J. Damzen V.J. Pinto-Robledo A.V. Kir’yanov J.J. Soto-Bernal 《Applied physics. B, Lasers and optics》2003,76(1):13-16
The analysis of compact CW diode-side-pumped grazing-incidence-geometry Nd:YVO4 laser designs is presented. An output power of 5 W (λ=1064 nm) was produced at 17 W of diode pump (conversion efficiency
of 30%) in single transverse TEM00 mode operation at high laser beam quality (Mx
2≈1.05 and My
2≈1.01). The resonator geometry was analyzed by applying generalized 4×4 matrix modeling of the spatial mode size, including
the impact on the laser operation of cavity astigmatism and a thermal lens in the laser slab. The simplicity and compactness
of the laser cavities allow their use for technological applications.
Received: 31 July 2002 / Published online: 22 January 2003
RID="*"
ID="*"Corresponding author. Fax: +44-20/7594-7744, E-mail: m.damzen@ic.ac.uk 相似文献
13.
An optical clock based on an Er3+ fiber femtosecond laser and a two-mode He–Ne/CH4 optical frequency standard (λ=3.39 μm) is realized. Difference-frequency generation is used to down convert the 1.5-μm frequency comb of the Er3+ femtosecond laser to the 3.4-μm range. The generated infrared comb overlaps with the He–Ne/CH4 laser wavelength and does not depend on the carrier–envelope offset frequency of the 1.5-μm comb. In this way a direct phase-coherent
connection between the optical frequency of the He–Ne/CH4 standard and the radio frequency pulse repetition rate of the fiber laser is established. The stability of the optical clock
is measured against a commercial hydrogen maser. The measured relative instability is 1×10−12 at 1 s and for averaging times less than 50 s it is determined by the microwave standard, while for longer times a drift
of the He–Ne/CH4 optical standard is dominant. 相似文献
14.
V. I. Gerasimova A. A. Antoshkov Yu. S. Zavorotny D. A. Lemenovskii 《Journal of Applied Spectroscopy》2012,79(2):203-210
Optical properties (photoluminescence and absorption) of Eu(bta)3(B) n (B = H2O or 1,10-phenanthroline) polycrystalline powders and fluoroacrylate polymers (FAPs) impregnated with these compounds using supercritical CO2 (SC CO2) were investigated. It was established that impregnation of Eu(bta)3phen into the FAPs using an SC CO2 solution was difficult to achieve. The type of B (ancillary ligand) and the polymer matrix were shown to influence the temperature quenching of photoluminescence of Eu3+ ions in the range 25–100°C. A comparative analysis of quantum yields (λex = 300 and 380 nm) and photoluminescence decay times (λex = 337.1 nm) for Eu(bta)3B n and for Eu(bta)3B n -doped FAPs was performed. 相似文献
15.
V. A. Gorobets V. O. Petukhov I. L. Yachnev V. A. Penniyainen E. V. Lopatina S. A. Podzorova B. V. Krylov 《Journal of Applied Spectroscopy》2010,77(3):413-418
We have built a wavelength-tunable CO2 laser meeting the requirements for low-intensity laser therapy. At λ = 10.57 μm and 9.24 μm, we observe a physiological effect
detectable from the change in the extent of neurite outgrowth from sensory neurons. This makes it possible to study molecular
mechanisms for interaction of low-intensity radiation with tissues in a living body. The ATP molecule is considered as the
specific molecular target for the action of the radiation. 相似文献
16.
C. Bauer P. Geiser J. Burgmeier G. Holl W. Schade 《Applied physics. B, Lasers and optics》2006,85(2-3):251-256
Stand-off technology for the remote detection of explosives and their traces on contaminated surfaces is a field of research that has recently gained much interest. Optical methods are well established in applications for counterterrorism because they facilitate analysis without contact between human being and hazardous materials. In this paper, to our knowledge for the first time, a remote stand-off detection system is developed by combination of pulsed laser fragmentation and pulsed mid-infrared laser absorption spectroscopy. Since the absorption of explosives is more efficient for infrared wavelengths laser radiation in the eye safe region around λ=1.47 μm rather than the conventional Nd:YAG laser line at λ=1.06 μm is preferred for the fragmentation. Generated product gases such as nitric oxide are probed by a synchronized distributed feedback quantum cascade laser (DFB-QCL) at λ≈5.3 μm. The ratio of NO and NO2 is a measure to distinguish between energetic and non-energetic materials. PACS 42.62.Fi; 07.07.DF; 42.55.Px 相似文献
17.
Ana Paula A. Marques Marcos Takashi S. Tanaka Elson Longo Edson R. Leite Ieda Lucia Viana Rosa 《Journal of fluorescence》2011,21(3):893-899
SrMoO4 doped with rare earth are still scarce nowadays and have attracted great attention due to their applications as scintillating
materials in electro-optical like solid-state lasers and optical fibers, for instance. In this work Sr1−xEuxMoO4 powders, where x = 0.01; 0.03 and 0.05, were synthesized by Complex Polymerization (CP) Method. The structural and optical
properties of the SrMoO4:Eu3+ were analyzed by powder X-ray diffraction patterns, Fourier Transform Infra-Red (FTIR), Raman Spectroscopy, and through Photoluminescent
Measurements (PL). Only a crystalline scheelite-type phase was obtained when the powders were heat-treated at 800 °C for 2 h,
2θ = 27.8° (100% peak). The excitation spectra of the SrMoO4:Eu3+ (λEm. = 614 nm) presented the characteristic band of the Eu3 + 5L6 transition at 394 nm and a broad band at around 288 nm ascribed to the charge-transfer from the O (2p) state to the Mo (4d)
one in the SrMoO4 matrix. The emission spectra of the SrMoO4:Eu3+ powders (λExc. = 394 and 288 nm) show the group of sharp emission bands among 523–554 nm and 578–699 nm, assigned to the 5D1→7F0,1and 2 and 5D0→7F0,1,2,3 and 4, respectively. The band related to the 5D0→7F0 transition indicates the presence of Eu3+ site without inversion center. This hypothesis is strengthened by the fact that the band referent to the 5D0→7F2 transition is the most intense in the emission spectra. 相似文献
18.
Single tracks and pairs of tracks are written in the volume of Pr-doped LiYF4-crystals using tightly focused femtosecond laser radiation (λ=1045 nm, τ
p=400–500 fs, f=0.1–1 MHz). Waveguiding between the tracks is demonstrated and optimized by varying the distance between the tracks and the
laser writing conditions. The stress-induced guiding mechanism is explained based on TEM, interference microscopy, near-field
and far-field measurements. It is shown that the single-crystalline material is getting poly-crystalline under femtosecond
laser irradiation. By measuring the lifetime of the 3P1→3H5 transition and the emission spectrum at excitation with λ=444 nm, no influence on these properties of the guided light is observed. This possibly enables the realization of a channel
waveguide laser in the visible spectral range. 相似文献
19.
Z. Zhu J. Li A. Brenier G. Jia Z. You X. Lu B. Wu C. Tu 《Applied physics. B, Lasers and optics》2007,86(1):71-75
Yb3+:GdAl3(BO3)4 (hereafter Yb3+:GAB) crystals with large sizes and good optical quality have been grown by the top-seed solution growth (TSSG) method. The polarized absorption and emission spectra have been investigated at room temperature. For the σ-polarization, the intensities of both absorption and emission spectra are stronger than those for the π-polarization, the σ-absorption cross section of Yb3+ in GAB being 3.43×10-20 cm2 at 977 nm, and the σ-emission cross section being 0.98×10-20 cm2 at 1045 nm. The fluorescence lifetime of the 2
F
5/2→2
F
7/2 transition was measured to be 800 μs in the 5% doped sample used for our laser experiments, 993 μs in a 10% doped sample and 569 μs in a 0.5% doped sample. The laser parameters were estimated as: βmin=0.022, Isat=10.4 kW/cm2 and Imin=0.23 kW/cm2. About 0.4 W laseroutput at the wavelength of 1043 nm was achieved when the Yb3+:GAB crystal was pumped by a 974 nm laser diode, with 27.4% slope efficiency. PACS 42.55.-f; 42.70.Hj; 78.20.-e; 81.10.Dn 相似文献
20.
A. Ivanchik D. Varshalovich P. Petitjean 《The European physical journal. Special topics》2008,163(1):191-196
Astronomical constraints on a possible cosmologicalvariation of the proton-to-electron mass ratio μ=mp/me are discussed. The analysis of H2 lines observed in thespectra of distant quasars Q 0405-443 (zem=3.02) andQ 0347-383 (zem=3.22) is performed [1] using, partly, very precise values of H2 frequencies from new laboratorymeasurements [2] and sensitivity coefficients from newaccurate calculations [2,3]. A possibleμ-variation
of Δμ/ μ= (2.0±0.6)×10-5over 12 Gyr is not excluded. However, the discussion of systematicerrors show that some may well be underestimated. Thus,
the abovevalue should be treated as the most stringent limit the cosmologicalvariation of μ at z≈2.6 - 3.0 (12 Gyr ago). 相似文献