Absolute Measurement of Second-Order Nonlinear Optical Coefficient of LiNbO3 by Parametric Processes

We have redetermined the absolute values of the nonlinear optical coefficient, d₃₁, of LiNbO₃ by parametric fluorescence and, for the first time, by difference frequency generation measurements to resolve the considerable discrepancy that existed between the values determined by second-harmonic generation (SHG) and parametric fluorescence. We obtain d₃₁ = 4.8±0.5 and 4.3±0.5 pm/V at the pump wavelengths of 488 and 532 nm, respectively, in reasonable agreement with the SHG data. It appears that the previous parametric fluorescence value, d₃₁=5.8 pm/V, was overestimated.Author to whom correspondence should be addressed.     

Characterization of second and third order optical nonlinearities of ZnO sputtered films

We measured the second and third order optical nonlinearity of zinc oxide, grown on glass substrates by the ion beam sputtering technique. Second and third harmonic generation measurements were performed by means of the rotational Maker fringes technique for different polarization configurations, thus allowing the determination of all non-zero components of the second order susceptibility at three different fundamental beam wavelengths, i.e., 1064 nm, 1542 nm and 1907 nm. The dispersion of the nonlinear optical coefficients has been evaluated, while the nonlinear optical coefficients were found to range between 0.9 pm/V and 0.16 pm/V for d₃₃, 0.53 pm/V and 0.08 pm/V for |d₁₅|, 0.31 and 0.08 pm/V for |d₃₁|, with increasing wavelength. Finally, one third order susceptibility, χ_ijkl ⁽³⁾, has been determined by third harmonic generation measurements at a fundamental wavelength λ=1907 nm and a value for χ₃₃₃₃ ⁽³⁾ of 185×10^-20 m²/V² has been found. PACS 42.65.An; 42.65.Ky; 42.70.Nq     

Polarized fluorescence spectra analysis of Yb:KGd(WO4)2

The average fluorescence wavelength of the laser crystal is the most important factor in the radiation-balanced laser (RBL). Polarized fluorescence spectra measurements of the anisotropic laser material ytterbium-doped potassium gadolinium tungstate, Yb³⁺:KGd(WO₄)₂, are carried out along principal refractive index directions m, p, g in three configurations in order to achieve the best design for RBL. The average fluorescence wavelength of g polarization is the shortest, so g should be in the face of fluorescence emission; m polarization should be normal to that face to avoid its strong absorption to fluorescence photons. Fluorescence re-absorption causes the average fluorescence wavelength of the directly measured spectra red-shifted at least 9 nm. Methods for depressing radiation trapping are suggested accordingly, which are high power pumping, low doping concentration, small dimensions and fusing with undoped KGd(WO₄)₂.     

Second harmonic generation in zinc oxide nanorods

Second-order optical nonlinearities of zinc oxide (ZnO) nanorods grown on quartz substrate were determined by optical second harmonic generation (SHG) measurements at 1064 nm fundamental wavelength. The average length of the zinc oxide nanorods ranged from 50 nm to 700 nm. By employing the Maker fringes technique, we obtained the second-order nonlinear optical coefficients d₃₃₃ and d₃₁₁. Their magnitudes and ratio are compared with that of zinc oxide thin film fabricated by different techniques. We see variations of the second-order nonlinear optical coefficients with respect to the aspect ratio of the nanorods. This is attributed to local field effects. PACS 42.65.Ky; 78.67.-n; 81.07.-b     

Observation of upconversion fluorescence and stimulated emission based on three-photon absorption

The observations of three-photon-induced frequency-upconversion fluorescence and the highly directional stimulated visible emission in two dyes, 4-[p-(dicyanoethylamino) styryl]-N-methylpyridinium iodide (abbreviated as CEASP) and the complex of CEASP and Ce(NO₃) (abbreviated as CEASP-Ce), are reported. The photographs of the forward amplified spontaneous emissions spots, pumped by an optical parametric oscillator idler with a pulse width of 8 ns and a wavelength of 1.3 μ m, are shown. The upconversion fluorescence produced both in dimethyl formamide solution and 2-hydroxyethyl methacrylate (HEMA) polymer spans from green to red, with a cubic dependence on the pump light intensity. The experimental results imply that the existence of the lanthanide ion Ce^{3 +} sensitizes the nonlinear absorption and emission.     

镱铝共掺石英玻璃的制备及其发光特性的研究

提出了一种新的溶液掺杂与非化学气相沉积(non-chemical vapor deposition, NCVD)熔融相结合的方法制备稀土掺杂石英基玻璃,并采用该方法制备出组分为98SiO₂-0.5Yb₂O₃-1.5Al₂O₃wt%、折射率n_D =1.519和密度 ρ=2.62 g/cm³的镱铝共掺石英玻璃.经实验测试表明:它的 关键词： 镱铝共掺石英玻璃 溶液掺杂 发光特性 光子晶体光纤     

Thermal Near Field and the Possibilities of Its Use for In-Depth Temperature Diagnostics of Media

We discover experimentally the effect of an electromagnetic thermal near field of a lossy medium. The effective depth d_eff of the layer in which the received signal is formed is found to be less than the skin-layer depth d_sk and is a function of the size D of the receiving antenna and its height h above the medium surface. The dependence d_eff(D,h) is obtained from measurements of the emission from a temperature-stratified water medium at a wavelength of 31 cm using a specially developed, electrically small antenna. The results of experimental studies of radiophysical parameters of the antenna are presented. We propose to use measurements of the dependence of the received emission on D and h as a new source of information on the in-depth temperature distribution. Methods for solving the corresponding inverse problems are developed, and the first results of retrieval of the subsurface temperature profile of a water medium are obtained.     

Complementary Methods of Processing diS-C3(3) Fluorescence Spectra Used for Monitoring the Plasma Membrane Potential of Yeast: Their Pros and Cons

Carbocyanine dye diS-C₃(3) was repeatedly employed in monitoring the plasma membrane potential of yeast and other living cells. Four methods of measuring and evaluating probe fluorescence signal were used in different studies, based on following fluorescence parameters: fluorescence intensity emitted within a certain spectral interval, F(580)/F(560) fluorescence emission ratio, wavelength of emission spectrum maximum, and the ratio of respective fluorescence intensities corresponding to the diS-C₃(3) bound to cytosolic macromolecules and remaining dissolved in the aqueous cell medium (i.e., unbound, or free). Here we show that data corresponding to the three latter spectral assessments of diS-C₃(3) accumulation in cells is mutually convertible, which means that their alternative use cannot lead to ambiguities in the interpretation of the results of biological experiments. On the other hand, experiments based on the effortless measurements of fluorescence intensities should be interpreted cautiously because controversial results can be obtained, depending on the particular choice of cell-to-dye concentration ratio and emission wavelength.     

Z-scan determination of the third-order optical nonlinearities of an azo dye using diode-pumped Nd:Yag laser

Optical nonlinearity of dye solutions are studied with considerable interest for their wide spread applications ranging from gain media in lasers to all-optical processing signal devices. The third-order nonlinear optical properties of Brilliant Crocein dye was measured by the Z-scan technique and measurements were carried out for different concentrations. The negative sign of the nonlinear refractive index n₂ indicates that this material exhibits self-defocusing optical nonlinearity and purely saturation absorption at the wavelength 532 nm of the diode-pumped Nd:YAG. These results show that Brilliant Crocein has potential applications in nonlinear optics.     

High Accuracy and High Sensitivity Measurements of the Electrooptic Effect in Undoped and MgO-Doped LiNbO3 Crystals

Accurate measurements of the composite electrooptic (EO) coefficients r_c consisting of the EO coefficients r₁₃, r₃₃, and the piezoelectric constant d₃₁ in undoped and MgO-doped LiNbO₃ (LN) were made by extracting the fundamental and third harmonic components from photo-detection signals of the parallel Nicol optics including the LN crystal driven by minimal sinusoidal voltage. The analysis of relationship between multiple-reflection rays in the EO crystal and the accuracy of measurement indicates that anti-reflection films must be coated on the end faces of the crystal for highly accurate measurements. Measured values of r_c of undoped and MgO-doped LN crystals at a wavelength of 632.8 nm were 19.8 ± 0.1 pm/V and 19.2 ± 0.1 pm/V, respectively.     

Thermally Stable and Resonance Enhanced Large Nonlinear Optical Properties In Poled Silica Films Doped with Thiazole Azo Dye

Sol-gel processed poled silica films doped with novel nonlinear organic materials, thiazole azo dye (TA), are prepared in high concentration. Resonance enhanced second-order nonlinear optical coefficient of d₃₃ = 154 pm/V is obtained from TA doped silica film (40 wt%) for the fundamental wavelength of 1064 nm. The value d₃₃ is unvaried for at least 100 h under a high temperature condition (100°C) without any relaxation. Wavelength dependent second-order nonlinearity is also measured.     

Depth profiling of dopants implanted in Si using the synchrotron radiation based high‐resolution grazing emission technique

We report on the surface‐sensitive grazing emission X‐ray fluorescence technique combined with synchrotron radiation excitation and high‐resolution detection to realize depth‐profile measurements of Al‐implanted Si wafers. The principles of grazing emission measurements as well as the benefits offered by synchrotron sources and wavelength‐dispersive detection setups are presented. It is shown that the depth distribution of implanted ions can be extracted from the dependence of the X‐ray fluorescence intensity on the grazing emission angle with nanometer‐scale precision provided that an analytical function describing the shape of the depth distribution is assumed beforehand. If no a priori assumption is made, except a bell shaped form for the dopant distribution, the profile derived from the measured angular distribution is found to reproduce quite satisfactorily the depth distribution of the implanted ions. Copyright © 2012 John Wiley & Sons, Ltd.     

Steady-State and Time-Resolved Fluorescence Polarization Behavior of Acenaphthene

Steady-state and time-resolved fluorescence polarization studies have been carried out on acenaphthene (ACE) in low-temperature glass solutions and at room temperature. In the low-temperature glass the fluorescence polarization values vary considerably with both emission and excitation wavelength. There is a time dependence (on the nanosecond time scale) of the fluorescence anisotropy, r(t), at 77 K, which has a strong dependence upon the excitation and emission wavelengths. Under these conditions, the time-dependent decay of the anisotropy is not attributable to chromophoric motion. The observations are consistent with emission from two closely lying and interconverting excited states. Rate constants for the photophysical processes involved have been determined by fitting the data using a model proposed by Fleming et. al. The results are discussed with particular reference to the care required in using dynamic fluorescence polarization measurements to determine energy transfer rates in systems containing this chromophore.     

La/B4C small period multilayer interferential mirror for the analysis of boron

An La/B₄C multilayer interferential mirror with small period d (4.8 nm) was produced by diode sputtering for the detection of the boron K emission by wavelength‐dispersive x‐ray spectrometry at a large Bragg angle (close to 45°). The structure of the mirror was characterized by grazing incidence x‐ray reflectometry and its performance at the energy of the boron K emission (183 eV) was evaluated by means of polarized synchrotron radiation. Spectrometric measurements showed that the La/B₄C mirror improved the detection limit of boron using by a factor of 2 with respect to similar Mo/B₄C mirrors and by a factor of 4 with respect to a lead stearate crystal. Copyright © 2005 John Wiley & Sons, Ltd.     

All solid-state continuous-wave Nd:YAG laser at 1319 and 659.5 nm under direct 885 nm pumping

The continuous-wave high efficiency laser emission of Nd:YAG at the fundamental wavelength of 1319 nm and its 659.5-nm second harmonic obtained by intracavity frequency doubling with an LBO nonlinear crystal is investigated under pumping by diode laser at 885 nm (on the ⁴ F _3/2 → ⁴ I _13/2 transition). An end-pumped Nd:YAG crystal yielded 9.1 W at 1319 nm of continuous-wave output power for 18.2 W of absorbed pump power. The slope efficiency with respect to the absorbed pump power is 0.55. Furthermore, 5.2 W 659.5 nm red light is acquired by frequency doubling, resulting in an optical-to-optical efficiency with respect to the absorbed pump power of 0.286. Comparative results obtained for the pump with diode laser at 808 nm (on the ⁴ F _5/2 → ⁴ I _13/2 transition) are given in order to prove the advantages of the 885 nm wavelength pumping.     

Modified electrochemical emission spectroscopy (MEES) As technique of NDT for detection localized corrosion of copper alloys in seawater

An early stage of localized corrosion, i.e., pitting and crevice corrosion, of a pure copper and a brass in uncoated and coated conditions in seawater was investigated in situ by a new non-destructive testing (NDT) method. The new method of localized corrosion detection is based on the optical corrosion-meter for measuring the corrosion current density (J) and on a modified electrochemical noise technique for determining the corrosion admittance (A_c) at the open-circuit potential of the alloys in solutions. The observations of localized corrosion were basically interferometric perturbations detected by the optical corrosion-meter only on the uncoated copper and the coated brass at the beginning of the tests. The interferometic perturbations interpreted as a localized corrosion in the form of an early pitting and crevice corrosion, of a depth ranging from 0.3 μm to several micrometers, of the uncoated copper and the coated brass, respectively. Also, the early stage of localized corrosion of the same alloys in the same conditions was determined in situ by a modified electrochemical noise (EN) technique, called the modified electrochemical emission spectroscopy (MEES) technique, simultaneously during the optical interferometry measurements. Determinations of localized corrosion by the MEES technique were electrochemical noise spectra detected on corrosion admittance (A_c)-time plots of the alloys in solutions. The corrosion admittance parameter, A_c=(dJ/dV), which defined the MEES technique, is capable of indicating localized corrosion and uniform corrosion activities. In this investigation, the parameter A_c was modified in which the change of the corrosion current density (dJ) was measured by the optical corrosion-meter rather than by the zero resistance ammeter, which is usually used for measuring the dJ in electrochemical noise technique. Consequently, results of the present work indicate that optical corrosion-meter as an electromagnetic method of measuring the corrosion current density, and MEES technique, as an electronic method for determining the A_c, are very useful techniques as non-destructive methods for the detection of localized corrosion at the initiation stage of the phenomenon.     

Ag:Bi2O3复合膜的线性和非线性光学性质

从实验和理论两个方面，探讨了金属Ag不同掺杂浓度对Ag:Bi₂O₃复合膜线性和非线性光学性质的影响. 用吸收光谱研究了Ag浓度与Ag:Bi₂O₃复合膜表面等离子体共振带之间的关系；用皮秒Z-扫描技术研究了共振和非共振情况下(激发光波长分别为532nm和1064nm)，金属Ag浓度与复合膜三阶非线性极化率的关系. 基于表面等离子体共振理论和局域场增强理论对复合膜进行了分析，得到了不同Ag浓度时Ag:Bi₂O₃复合膜的三阶非线性效应，研究了激发波长和金属浓度对复合膜线性和非线性光学性质的影响. 结果表明，等离子体共振增强和合适的金属掺杂浓度使得三阶极化率增强二个量级，在Ag浓度为35％左右和接近等离子体共振频率(相应吸收带位于560nm—622nm)的532nm激发时，χ⁽³⁾具有最大值2.4×10^-9esu. 关键词： 金属纳米颗粒 复合膜 三阶非线性 表面等离子体共振     

Sn-state lifetime determination of dyes

The S _n -state lifetime is determined from two-step excited S _n -S₀fluorescence yield measurements with picosecond light pulses. The theoretical analysis includes single pulse and double pulse consecutive excitation and takes into account the anisotropy of excitation and emission. Experimental results of the single pulse two-step excitation technique are presented for the S₄-state lifetimes of the three mode-locking dyes 5, 9740 and 9860 for Nd-glass lasers.     

Accurate whole-spectrum measurements of intracellular pH and [Na+]

Fluorescent measurements of intracellular H⁺ and Na⁺ are improved by using whole spectra of the fluorescent indicators BCECF and SBFI, respectively. The extra data in whole spectra enable both an accurate calibration and a ready detection of artifacts which are not possible to identify using a more conventional data analysis that relies upon only two wavelength windows in the fluorescence spectra. The whole-spectrum technique is applicable to cell suspensions in a conventional fluorimeter (as is reported here with SBFI), as well as to attached cells using a fluorimeter combined with an inverted epifluorescence microscope. The spectral method was highly reproducible in that pairs of successive pH measurements differed, on average, by only 0.01±0.02 U. Random uncertainty from sample to sample was estimated numerically from the standard deviation of measurements on ionophore-treated cells. When full-spectrum analysis was employed, this scatter showed a two-fold improvement over results obtained using the two-wavelength ratio method. Because SBFI has a relatively narrow dynamic range, whole-spectrum analysis has been applied to improve the accuracy of sodium determinations. The calibrated system measured [Na⁺]_i with excellent linearity over the range 2–150 mM and with an accuracy of approximately 5 mM.     

Fluoreszenz der magnetisch ordnenden Halbleiter EuS,EuSe und EuTe

The photoluminescence properties of the europium-chalcogenides EuS, EuSe and EuTe are described. Below approximately 150°K these compounds show a characteristic near-infrared fluorescence band with a half-width of about 0.25 eV. This radiative recombination is ascribed to an intrinsic transition 4f ⁶ 5d→4f ⁷ of the Eu-ions. Its important frequency shift with respect to the corresponding optical absorption in the vicinity of the absorption edge is due to a Franck-Condon-type relaxation process. The spectral band position and the quantum efficiency of the emission are found to be very sensitive to magnetic ordering. Within the series of substances the different kind of magnetic order is clearly illustrated by the dissimilar spontaneous fluorescence behaviour: On cooling, the ferromagnet EuS displays a red shift and a quenching of the emission nearT _c, whereas the antiferromagnet EuTe shows a blue shift of the band and an increase of its intensity nearT _N. With respect to this behaviour in zero field an applied magnetic field causes the fluorescence to be quenched and shifted towards longer wavelengths. The largest response to the field is observed in the vicinity of the ordering temperatures and in the metamagnetic temperature range of EuSe. The results are discussed in connection with measurements of the magnetization, the optical absorption and the photoconductivity and compared with fluorescence measurements on Eu(II)-silicates. The behaviour of the excitation spectra is closely related to the absorption edge shift. On the other hand the shift of the emission is not similarly discribed by the mean ion spin correlation. We propose to ascribe this to a magnetic relaxation in the vicinity of the excited state. The unusual intensity behaviour is also discussed.