Evaluation of toxic agent effects on lung cells by fiber evanescent wave spectroscopy

Biochemical changes in living cells are detected using a fiber probe system composed of a single chalcogenide fiber acting as both the sensor and transmission line for infrared optical signals. The signal is collected via evanescent wave absorption along the tapered sensing zone of the fiber. We spectroscopically monitored the effects of the surfactant Triton X-100, which serves as a toxic agent simulant on a transformed human lung carcinoma type II epithelial cell line (A549). We observe spectral changes between 2800-3000 cm(-1) in four absorptions bands, which are assigned to hydrocarbon vibrations of methylene and methyl groups in membrane lipids. Comparison of fiber and transmission spectra shows that the present technique allows one to locally probe the cell plasma membrane in the lipid spectral region. These optical responses are correlated with cellular metabolic activity measurements and LDH (lactate dehydrogenase) release assays that indicate a loss of cellular function and membrane integrity as would be expected in response to the membrane solubilizing Triton. The spectroscopic technique shows a significantly greater detection resolution in time and concentration.     

Infrared evanescent-absorption spectroscopy with chalcogenide glass fibers

We have used telluride glass fibers fabricated in house to measure the evanescent-absorption spectra of water, methanol, ethanol, isopropanol, acetone, ethanoic acid, hexane, and chloroform. Furthermore, detection limits of less than 2 vol. % solute were obtained for mixtures of water and methanol, ethanol, isopropanol, acetone, and ethanoic acid. Techniques to reduce the detection limits are discussed.     

Monolithic folded resonator for evanescent wave cavity ringdown spectroscopy

An optical resonator is characterized that employs both ultrahigh-reflective coated surfaces and total internal reflection to enable cavity ringdown spectroscopy of surfaces, films, and liquids. The monolithic folded design possesses a polarization-independent finesse that allows polarization-dependent phenomena, such as molecular orientation, to be probed. Although a restricted bandwidth (~15% of the design wavelength) results from use of reflective coatings, the resonator provides high sensitivity and facile operation. A minimum detectable absorption of 2.2 x 10(-6) was obtained for single laser shots by use of multimode excitation at 530 nm with an excimer-pumped, pulsed dye laser.     

Experimental evaluation of a hollow glass fiber

Very high interest in making a low-loss fiber for the infrared has been stimulated by important applications in optical communication, surgery, cutting, welding, and heat treatment. The leaky waveguide is one of the most promising types of future fiber in the infrared region where low-loss materials are not available or not suitable for making fibers (i.e., CO2 laser light lambda = 10.6 microm). In this paper a comparative model of a He-Ne laser beam and an oxide glass leaky hollow fiber for a CO2 laser light beam and a chalcogenide glass leaky hollow fiber are studied. Measurements of attenuation, dependence of output power on diameter and angle, and the angular dependence of output angle vs input angle were made. The experimental data were compared with theoretical calculations, and the critical value of the wall thickness for minimum attenuation is given.     

Theoretical analysis of the evanescent wave absorption coefficient for multimode fibre-optic evanescent wave absorption sensors

Abstract

In an optical fibre of circular cross section, leaky skew rays transmit power in a different way from trapped and meridional rays. In this paper, a theoretical analysis of the evanescent wave absorption coefficient for leaky skew rays in multimode optical fibre evanescent wave absorption sensors is presented. Further, a comprehensive expression for the effective evanescent wave absorption coefficient is obtained. Some numerical results are given to illustrate this theoretical analysis. This work could be applied to optimize the design of fibre-optic evanescent wave absorption sensors.     

Characterisation of the cross-linking process in an E-glass fibre/epoxy composite using evanescent wave spectroscopy

The term “self-sensing composites” is sometimes used to describe the case where the reinforcing glass fibres in advanced fibre-reinforced composites are used as the sensors for chemical process-monitoring (cure monitoring). This paper presents conclusive evidence to demonstrate that reinforcing E-glass fibres can be used for in situ cure monitoring. The cure behaviour of an epoxy/amine resin system was compared using evanescent wave spectroscopy via the reinforcing E-glass fibres and conventional transmission Fourier transform infrared spectroscopy. This paper also reports for the first time that evanescent wave spectroscopy via E-glass fibres can be used to detect the presence of silane coupling agents. Preliminary results indicated that the cure kinetics on the E-glass fibre surface, as observed using evanescent wave spectroscopy, were influenced by the silane coupling agent.     

Imaging single fluorescent molecules at the interface of an optical fiber probe by evanescent wave excitation

We have developed a new fluorescent method for single-molecule detection (SMD) and imaging using an optical fiber probe. The fluorophores were excited by the evanescent wave field produced on the core surface of the optical fiber. This was achieved by exposing a section of the core of the optical fiber probe to the fluorophore solution. Both cylindrical and square optical fiber probes were used for SMD. The fluorescent signals were detected by an intensified charge-coupled device. Single rhodamine 6G molecules have been detected. The number of rhodamine 6G molecules imaged by the optical fiber probe showed an excellent linear relationship with the concentrations of the fluorophores. The SMD scheme was also applied to the imaging of biomolecules, such as molecular beacon DNA molecules, labeled with tetramethylrhodamine. Our results have shown that using an optical fiber is an easy yet effective approach to SMD. It represents a simpler fluorescent method for the detection of single-molecules in solution and at an interface.     

Measurement of evanescent wave properties of a bulk acoustic wave resonator

Acoustic wave fields in a thin-film bulk acoustic wave resonator are studied using a heterodyne laser interferometer. The measurement area is extended outside the active electrode region of the resonator, so that wave fields in both the active and surrounding regions can be characterized. At frequencies at which the region surrounding the resonator does not support laterally propagating acoustic waves, the analysis of the measurement data shows exponentially decaying amplitude fields outside the active resonator area, as suggested by theory. The magnitude of the imaginary wave vectors is determined by fitting an exponential function to the measured amplitude data, and thereby the experimentally determined dispersion diagram is extended into the region of imaginary wave numbers.     

High-purity chalcogenide glasses for fiber optics

The data on the present degree of purity of chalcogenide glasses for fiber optics, on their methods of production and on the properties, which are essential for their actual application, are generalized. The content of limiting impurities in the best samples of chalcogenide glasses is 10–100 ppb wt.; of heterophase inclusions with size of about 100 nm is less than 10³ cm^?3. On the basis of chalcogenide glasses the multimode and single mode optical fibers are produced with technical and operation characteristics sufficient for a number of actual applications. The minimum optical losses of 12–14 dB/km at 3–5 µm are attained in the optical fiber from arsenic-sulfide glass. The level of losses in standard chalcogenide optical fibers is 50–300 dB/km in 2–9 µm spectral range. The factors, affecting the optical absorption of glasses and optical fibers, are analyzed, and the main directions in further development of chalcogenide glasses as the materials for fiber optics are considered.     

Photo-induced absorption changes in selenium-based chalcogenide glass films

The random network model for amorphous alloys proposed by White has been developed for some selenium-based amorphous semiconductors (GeSe and AsSe) annealed or irradiated with light. The model suggests that the photo-bleaching and the photo-darkening observed in these systems may be due to changes in the numbers of bonds.     

Weakly frequency-dependent electrical conductivity in a chalcogenide glass

We report the observation in a chalcogenide glass of a weakly frequency-dependent electrical conductivity obeying the usual empirical relation σ' (ω) ∝ωⁿ but with a much lower than normal value of the exponent n, in the range 0.1–0.25 instead of 0.6–1.0. We suggest that this behaviour may be more common than is normally appreciated and that it has implications for the theoretical interpretation of both the alternating and the direct current conductivity. A new technique of logarithmic complex impedance diagrams is also introduced to facilitate the analysis of data.     

Nonlinear pulse propagation in chalcogenide As2Se3 glass photonic crystal fiber using RK4IP method

Pulse propagation through chalcogenide As(2)Se(3) glass photonic crystal fiber (PCF) is numerically investigated using fourth-order Runge-Kutta in the interaction picture (RK4IP) method. The fully vectorial effective index method (FVEIM) is used to calculate the variation of effective refractive index, effective area, dispersion, and nonlinear coefficient (γ) in As(2)Se(3) PCF with wavelength for different values of pitch and air hole size. The RK4IP method is used to demonstrate the soliton propagation, self-phase modulation (SPM), soliton collision and cross phase modulation (XPM) in the designed As(2)Se(3) PCF. The numerically obtained value of soliton collision length (L(col)=51.3L(D)) using the RK4IP method is found to be in good agreement with the theoretical value of soliton collision length (L(col)=51.408L(D)) obtained from inverse scattering transform method, thus providing a verification of the RK4IP accuracy in solving generalized nonlinear schr?dinger equation (GLNSE). We also evaluate and apply the value of wavelength for distortionless (L(NL)=L(D)) propagation of the soliton pulse.     

Surface plasmon resonance spectroscopy based on evanescent field treatment

The reflectance in a surface plasmon resonance (SPR) curve can be expressed in terms of the integration of the product between the evanescent electric field and the imaginary part of the dielectric constant of all absorbing media. The evanescent field in the metal film consists of two fields, one originating at the prism/metal interface and the other at the metal/dielectric interface. Near the resonance angle, the evanescent field strength at the metal/dielectric interface is much greater than that at the prism/metal interface. The evanescent field in dielectric medium has a single origin at the metal/dielectric interface. Due to the optical enhancement at the interface, the amplitude of the evanescent electric field in the dielectric medium is much greater than that in the metal film. This field, however, is not being utilized in conventional SPR where changes in the refractive index of the nonabsorbing dielectric media are of interest. In a system with an absorbing dielectric medium, the absorption of the medium is enhanced by the strong evanescent electric field. The evanescent field distributions in the metal film and in the dielectric medium are significantly altered by the absorbing dielectric, which results in shifting of the resonance angle, increasing of the reflectance, and broadening of the SPR curve. Since the absorption contribution from the absorbing dielectric can be separated from that of the metal film via knowledge of evanescent field distribution, an in-depth analysis of the SPR curve of an absorbing medium and its relationship with the material characteristics are possible.     

Ge-Ga-S-CdS玻璃的电致二次谐波发生特性

用熔融-急冷法制备了Ge14Ga3S37(CdS)3硫系玻璃样品,使用Maker条纹法观察了电场-温度场极化样品中的二次谐波发生(SHG)现象,研究了极化条件对SHG强度的影响、该效应产生的机理以及SHG现象室温下的稳定性.结果表明,极化样品中存在明显的二次谐波发生现象,入射角在±(40～50)°左右时,SHG的相对强度出现最大值;SHG的强度随着极化电压的增大和极化时间的延长而逐渐增强并渐趋饱和;在5 kV、280℃、30分钟的极化条件下,极化样品的二阶非线性极化系数χ(2)达到最大值4.36 pm/V;根据偶极子取向模型阐释了SHG产生机理以及极化条件对样品二阶光学非线性系数大小的影响机制;发现玻璃的电致极化区域位于阳极表面以下十几微米的区域,SHG效应在室温下是稳定的.     

Transmission line protection with thin film chalcogenide glass devices

We present the theoretical analysis of a lossless transmission line excited by voltage pulses of the type associated with high altitude nuclear explosions or with lightning. The line is protected by a thin film chalcogenide glass ovonic threshold switch (OTS). The OTS is very simply modelled as a lumped parameter network, and its OFF-ON transition is represented by a time-varying resistance which is characterized by a time constant τ. The analytical solution for the voltage transients along the line considers the applied voltage pulse as a succession of narrow component pulses whose effect is computed according to the value of the time-varying reflection coefficient at the device location. The analytical solution includes the effect of multiple reflections, and it is evaluated numerically so as to determine the voltage profile along the line. We show that the OTS device is well suited for electromagnetic pulse line protection. The effects of the delay time and of the values of the OFF and ON resistances of the switch are discussed.     

冷却方式对硫系玻璃性能的影响

通过DSC、XRD、SEM、FT-IR和显微硬度测试等分析手段,研究了冷却方式对99.75Ge23Se67Sb10-0.25RbI玻璃组织、热稳定性以及光学和力学等性能的影响。结果表明,采用空冷制得的试样在8~12μm波段红外透过率达70%以上,高于水冷试样(64%),但由于空冷冷速慢,氢在硒中的固溶度大,导致杂质吸收也大于水冷试样;空冷试样在280℃热处理20h可从XRD检测发现明显Sb2Se3和GeSe2的结晶峰,而水冷试样在300℃热处理20h后才能检测到结晶峰;经过热处理,水冷试样的最大KIC值可达到0.414 MPa·m1/2,较未热处理值提高了26%,且高于空冷试样的最大KIC(0.368 MPa·m1/2),因此,水冷试样高温稳定性好,断裂韧性较大,更适合用作微晶化硫系红外玻璃。     

Study of curing process of glass fiber and epoxy resin composite by FT-NIR,photoacoustic spectroscopy and luminescence spectroscopy

This article investigates the application of the luminescence spectroscopy technique in steady-state conditions to study the glass fiber–epoxy F155 prepreg. The study was conducted by comparing the results obtained from the intrinsic fluorescence with the data obtained by application of Fourier Transform Near Infrared spectroscopy (FT-NIR) and photoacoustic spectroscopy in the medium infrared spectroscopy (PAS) to the same material. Extrinsic fluorescence of 9-anthroic acid (9-AA) was also used. Infrared spectroscopy with Fourier transform the medium region (FT-IR) was also used to characterize the epoxy resin. Prepregs containing 9-AA or not were heat treated at 121 °C (F-155) for 360 min at a 2 °C/min heating rate. The results obtained by both methods indicated that the cross-linking reaction can be monitored by analyzing the spectrometric changes of the emission bands of the prepreg and 9-AA. The intrinsic emission at 368 nm was used to calculate the conversion degree. The photophysical behavior of 9-AA probe indicated a reduction of free volume of the polymeric matrix with curing process.