Wavelength Of Light Source Research Articles

Indocyanine green-mediated photodynamic therapy on glioblastoma cells in vitro

Photodynamic therapy (PDT) is an alternative therapy which is administered with non-toxic drugs, called photosensitizers (PSs) , along with irradiation at a specific wavelength of light to damage tumor cells. Different wavelengths of light sources and photosensitizers have been investigated in treatment of many cancer types. In this study, we investigated whether photodynamic therapy using indocyanine green (ICG), also a cyanine dye used in medical diagnostics, can be used to inhibit cell proliferation of glioblastoma. Glioblastoma cells were irradiated with a diode laser ( λ = 809 nm, 100 J cm −2 ) in continuous wave operation mode. Cell proliferation was measured by XTT assay at 24 h after light irradiation. While only ICG application (10 µg/ml and 50 µg/ml concentrations) had no effects on glioblastoma cell proliferation, ICG in combination with laser irradiation (ICG-PDT) caused a significant decrease of cell proliferation. In conclusion, ICG-PDT may be valuable therapeutic approach as potential treatment for cancer such as glioblastoma. The results could be used as primary data for efficacy of ICG-PDT on malignant tumors.

Sine-modulated wavelength-independent full-range complex spectral optical coherence tomography with an ultra-broadband light source

We present a full-range complex spectral domain optical coherence tomography with an ultra-broadband light source based on sinusoidal modulation. For the sinusoidal modulation strategy, a lead zirconate titanate stack actuator is employed to achieve the sinusoidal vibration of a mirror and therefore to get a series of spectral interferogram with different phase delays. The purpose of this strategy is to get higher performance complex-conjugate artifact elimination. Bessel separation of the signal sequence at each wavelength of the spectrometer was used to reconstruct the real and imaginary components of interference fringes; however, the sinusoidal modulation method is independent of light source wavelength. The experimental results demonstrated that the method had an excellent performance in a complex-conjugate suppression of 50 dB for a full width at half maximum bandwidth of 236 nm, and it has better anti-artifact ability and more flexible range in phase shifting than the conventional wavelength-dependent phase-shifting method on a full-range complex spectral optical coherence tomography system. Furthermore, the effect of the hysteresis error of lead zirconate titanate actuators on the performance of complex-conjugate artifact elimination was investigated and the solution of lead zirconate titanate positioning performance for both conventional phase-shifting and sine-modulation methods was suggested.

Evaluation of Anisotropic Biaxial Stress in Si1-X Ge x /Ge Mesa-Structure by Oil-Immersion Raman Spectroscopy

Introduction Silicon Germanium (Si1-x Ge x ) is recognized as a material for the next-generation transistor device [1]. In particular, Si1-x Ge x is attractive as a channel material that has higher carrier mobility than Si. Furthermore, strain engineering is also valid for Si1-x Ge x similar to the Si to improve transistor performance. Nowadays, complicated nanostructures, such as FinFET, has used in the devices. Thus, the strain (stress) states in Si1-x Ge x nanostructures should be complicated because of hetero junction and nanoscalling processes [2]. In the nanostructure devices, accurate evaluation of anisotropic biaxial stress states is indispensable. In our previous report, we demonstrated the evaluation of the anisotropic biaxial stress states in various nanostructures including strained Si1-x Ge x with low Ge concentration on the Si substrate by oil-immersion Raman spectroscopy [3,4]. In this study, we investigated the biaxial stress states in Si1-x Ge x mesa structure with high Ge concentration on Ge substrates depending on nanostructure size by oil-immersion Raman spectroscopy. Experiments Si1-x Ge x films were epitaxially grown on the Ge substrate (Si1-x Ge x /Ge) whose Ge concentration were approximately x = 0.76, 0.85, and 0.92. The film thicknesses of the samples were 50, 76, and 35 nm, respectively. Furthermore, the various size mesa structures were fabricated by electron beam lithography and reactive ion etching. Figure 1(a) and (b) show the schematic of the Si1-x Ge x mesa structure and cross-sectional TEM image (x = 0.76). The sample widths (Ws) were 1.0, 0.5, 0.2, 0.1, and 0.05 μm, while the length (L) was fixed at 3.0 μm. In the oil-immersion Raman measurements, the anisotropic biaxial stresses in the strained Si1-x Ge x were evaluated. The numerical aperture was 1.4 and the refraction index in the atmosphere was 1.5. The excitation light source wavelength and the spectroscope focal length were 532 nm and 2,000 mm, respectively. Results and Discussion Figure 2 shows Raman spectra from the Si1-x Ge x mesa structures with various Ge concentration, where the width of W = 1.0 μm. These spectra were calibrated by the Ge substrate peak at 300 cm-1. From the result, the peaks of Si1-x Ge x with lower Ge concentration were observed at lower wavenumber side. The peak shift was caused by the combination of decreasing Ge concentration and increasing tensile stress. Figure 3 shows the biaxial stresses σ xx and σ yy in the Si1-x Ge x with x = 0.76. Here, the variation of σ xx and σ yy were clearly observed. The stress variation was depending on the width of mesa structure (W). As a result, σ yy was more relaxed than σ xx with decreasing of the width. Furthermore, σ yy was dramatically decreased at less than W = 0.2 μm, while σ xx remains almost constant through W = 1.0, 0.5, 0.2 μm. This result demonstrates that the biaxial stress state was clearly depend on the Si1-x Ge x mesa structure W width. We believe that it is important to evaluate anisotropic biaxial stress states. Therefore, oil-immersion Raman spectroscopy is useful for the stress engineering. Acknowledgement This study was partially supported by the Japan Society for the promotion of Science through a Grant-in-Aid for Scientific Research B (No. 24360125) and Funding program for World-Leading innovative R&D on Science and Technology.

Investigation of electron transfer processes involved in DSSC’s by wavelength dependent electrochemical impedance spectroscopy (λ-EIS)

For two decades, DSSC’s have shown promising performance for high yielding conversion of solar energy to electricity under mild conditions. However, the related investigation techniques rely either on pure electrochemical techniques regardless of the light source wavelength either on photochemical processes with a poor electrochemical description. The present study aims at bridging together these two domains using electrochemical impedance spectroscopy (EIS) through wavelength scanning using a monochromator. The main electrochemical features of the DSSC and parameters of the EIS model were examined depending on light wavelength. The technique has been developed at open circuit voltage, using the Ru-based N719 sensitizer impregnating a thin mesoscopic TiO2 layer, with I2/I− mediating redox couple. Tests were carried out with and without mediator, thus resulting in precise interpretation of the various electron transfers occurring at the photo-anode. The time constants of the various processes involved could be obtained without the use of transient absorption or emission spectroscopy: comparison of the data with formerly published results could validate the original method. Moreover interpretation of the wavelength-dependent spectra revealed the existence of two deactivation processes in the cell — which have been identified and quantified — depending on the density of excited states generated at the SC-electrolyte interface. Finally, in relation to IPCE measurements and absorption spectra, the exchange current density of the cathode for I− regeneration was also found affected by wavelength. The approach could be applied to non-zero currents and to other sensitizer-semiconductor systems.

Antimicrobial Effects of Photodynamic Therapy Using Blue Light Emitting Diode with Photofrin and Radachlorine against Propionibacterium acnes

Photodynamic therapy (PDT) apply photosensitizers and light. The purpose of this study was to evaluate the in vitro efficacy of PDT using blue LED (light emitting diode) with photofrin and radachlorin for Propionibacterium acnes. The colony forming units method was used to assess the antibacterial activity. Suspension (1 mL) containing P. acnes at 1×105 CFU/mL were prepared and then 2 fold serial diluted to 12.5 g/mL from 50 g/mL concentration of photofrin and radachlorin. After 60 minutes incubation, light was irradiated for 10 to 30 minutes using the following light source of wavelength 460 nm, each energy density 36, 72 and 108 J/cm2. Bacterial growth was evaluated after 72 hours incubation in a Phenylethanol Blood Agar (PEBA) culture. In addition, flow cytometric analysis were performed to measure the live cell after PDT. Also transmission electron microscopy (TEM) was employed to evaluate the effect of pathogens by PDT. The PDT Group was perfectly killed to all kind of photosensitizers dose of 12.5 g/mL with irradiation of 10 minutes. Also other Groups were killed to all kind of photosensitizers dose of 6.25 g/mL with irradiation time of 20 and 30 minutes. The flow cytometry showed a lower number of viable bacteria in the PDT group compared to the control group. The images of the TEM results were showed in cytoplasmic membrane damage and partially deformed to cell morphologies. These results suggest that radachlorin and photofrin combine blue LED PDT can be effectively treated when was proved treatment for acnes therapy.

Wavelength-adaptive dehazing using histogram merging-based classification for UAV images.

Since incoming light to an unmanned aerial vehicle (UAV) platform can be scattered by haze and dust in the atmosphere, the acquired image loses the original color and brightness of the subject. Enhancement of hazy images is an important task in improving the visibility of various UAV images. This paper presents a spatially-adaptive dehazing algorithm that merges color histograms with consideration of the wavelength-dependent atmospheric turbidity. Based on the wavelength-adaptive hazy image acquisition model, the proposed dehazing algorithm consists of three steps: (i) image segmentation based on geometric classes; (ii) generation of the context-adaptive transmission map; and (iii) intensity transformation for enhancing a hazy UAV image. The major contribution of the research is a novel hazy UAV image degradation model by considering the wavelength of light sources. In addition, the proposed transmission map provides a theoretical basis to differentiate visually important regions from others based on the turbidity and merged classification results.

Straight, conic and circular fringes in single interferogram

Interferometry is an important part of optics courses taught at the undergraduate level in universities throughout the world. It is used to explain to students the wave nature of light and is also used to measure parameters like length, refractive index, thickness of test samples and wavelength of light source, etc. The shape of interference fringes (linear, conic or circular) gives vital information about the interfering wavefronts and is used for firsthand visual inspection in optical shop testing and other applications of scientific and engineering importance. The present work describes a simple laboratory technique to generate fringes with different shapes in a single interferogram. This is achieved by using our diffraction-Lloyd mirror interferometer where two portions of the diffracted field are superimposed to generate the interference fringes. The technique is quite helpful in explaining the role of source orientation on the shape of interference fringes to students.

Experimental study for depth estimation of absorber with two wavelength light sources

Experimental study for depth estimation of absorber with two wavelength light sources

Experimental study for depth estimation of absorber with two wavelength light sources

Experimental study for depth estimation of absorber with two wavelength light sources

Electrochromic properties of bipolar pulsed magnetron sputter deposited tungsten–molybdenum oxide films

There are great interests in electrochromic technology for smart windows and displays over past decades. In this study, the WMoOx thin films were deposited onto indium tin oxide glass and silicon substrates by pulsed magnetron sputter system with W and Mo targets. The films were deposited with fixed W target power while the variant parameter of Mo target power in the range 50, 100, 150 and 200W was investigated. The working pressure was fixed at 1.33Pa with a gas mixture of Ar (30sccm) and O2 (15sccm). The film thickness increased with the Mo target power. Higher plasma power resulted in a crystalline structure which would reduce the electrochromic property of the film. The influence of plasma powers applied to Mo target on the structural, optical and electrochromic properties of the WMoOx thin films has been investigated. WMoOx films grown at Mo target powers less than 100W were found to be amorphous. The films deposited at 150W, which is the optimal fabrication condition, exhibit better electrochromic properties with high optical modulation, high coloration efficiency and less color memory effect at wavelength 400, 550 and 800nm. The improvement resulted from the effect of doping Mo has been tested. The maximum ΔT (%) values are 36.6% at 400nm, 65.6% at 550nm, and 66.6% at 800nm for pure WO3 film. The addition of Mo content in the WMoOx films provides better resistance to the short wavelength light source and can be used in the concerned application.

Polymer nanopillar-gold arrays as surface-enhanced Raman spectroscopy substrate for the simultaneous detection of multiple genes.

In our study, 2D nanopillar arrays with plasmonic crystal properties are optimized for surface-enhanced Raman spectroscopy (SERS) application and tested in a biochemical assay for the simultaneous detection of multiple genetic leukemia biomarkers. The special fabrication process combining soft lithography and plasma deposition techniques allows tailoring of the structural and chemical parameters of the crystal surfaces. In this way, it has been possible to tune the plasmonic resonance spectral position close to the excitation wavelength of the monochromatic laser light source in order to maximize the enhancing properties of the substrate. Samples are characterized by scanning electron microscopy and reflectance measurements and tested for SERS activity using malachite green. Besides, as the developed substrate had been prepared on a simple glass slide, SERS detection from the support side is also demonstrated. The optimized substrate is functionalized with thiol-modified capture oligonucleotides, and concentration-dependent signal of the target nucleotide is detected in a sandwich assay with labeled gold nanoparticles. Gold nanoparticles functionalized with different DNA and various Raman reporters are applied in a microarray-based assay recognizing a disease biomarker (Wilms tumor gene) and housekeeping gene expressions in the same time on spatially separated microspots. The multiplexing performance of the SERS-based bioassay is illustrated by distinguishing Raman dyes based on their complex spectral fingerprints.

Spectral Features of Photostimulated Oxygen Isotope Exchange and NO Adsorption on “Self-Sensitized” TiO2–x/TiO2 in UV–Vis Region

We have investigated the photoactivated O2 adsorption/desorption, the isotope equilibration (POIEq), and the isotope exchange (POIEx) in the O2–(TiO2–x/TiO2) (Degussa P-25) system, as well as the adsorption and POIEx in the NO–(TiO2–x/TiO2) systems. The photoactivation spectra of the hole centers Os– generation, of POIEq, and of the NO photoadsorption were measured in the 300–500 nm range using a continuously adjustable wavelength light source. The spectral characteristics of the NO photoadsorption are close to those of POIEq Both electron-donor and hole centers are manifested in these processes. For O2 photodesorption, CO oxidation, POIEx, and POIEq the hole centers Os– are responsible. In the case of O2 and NO photoadsorption both types of centers are active. The maxima of POIEq and of NO photoadsorption are placed near 420 nm beyond the edge of the TiO2 bandgap absorption. It was found that not only does the N18O–Ti16O2 exchange occurs under the illumination but also it can be activated by a preliminary sample illumination in vacuum as it was observed for POIEq. The photoactivation spectrum does not coincide with the absorption spectra of the F-type centers (F+ and F-centers, i.e., oxygen anion vacancies filled with one or two e–, respectively) and of Ti3+. The formation of the 2D structures, “core–shell” TiO2–x/TiO2, on the parts of the surface region and the decreasing of bandgap on these parts are supposed based on the kinetic data (the “fast” excitations in the bulk under UV irradiation and the “slow” excitations on the surface under the visible irradiation) and on the spectral data (maximum action is near 420 nm for both electronic and hole centers).

Evaluation of Anisotropic Biaxial Stress in Thin Strained-SiGe Layer Using Surface Enhanced Raman Spectroscopy

Introduction Silicon germanium (SiGe) is recognized as a high mobility channel material for the next-generation transistors in place of Si. Nowadays, various future devices using SiGe are being developed [1]. The accurate evaluation of strain (stress) is essential to realize future devices using SiGe. However, the evaluation of stress in thin SiGe layer is difficult because of poor signal embedded in those from huge amount of thick Si substrate [2]. We have previously reported that relatively weak TO phonon excitation in strained SiGe by oil-immersion Raman spectroscopy [3]. We also reported that the evaluation of anisotropic biaxial stress in strained Si on relaxed SiGe layer by exciting longitudinal optical (LO) and transversal optical (TO) phonons using surface enhanced Raman spectroscopy (SERS) [4]. In this study, the SERS measurements were performed to excite the TO phonon in strained SiGe layer more efficiently. Experiment The thin SiGe layer on Si substrate with approximately 30% Ge concentration was used as the sample. The thickness of the SiGe layer was approximately 38 nm. Undecane (C11H24) was used for the solvent of Ag nanoparticles. After spin-coating the Ag nanoparticles on the SiGe surface, the sample was sintered at 190 ›C for 5 min. The average diameter of Ag particles was approximately 30 nm (nominal value). Oil-immersion lens was used to enhance the SERS effect. The numerical aperture (NA) was 1.4 and the refraction index n was 1.5. On the other hand, in the conventional measurement, NA and n were 0.7 and 1.0, respectively. The wavelength of the excitation light source and the focal length of the spectroscope were 532 nm and 2,000 mm, respectively. Results and Discussion Fig. 1 shows the SEM image of the SiGe surface with the Ag nanoparticles. Fig. 2 shows Raman spectra from strained SiGe on the Si substrate coated (w/ SERS) and uncoated (w/o SERS) by the Ag nanoparticles. These spectra were normalized by the Si substrate peak at 520 cm-1. The relative intensity of the SiGe peak was dramatically enhanced and the peak position of SiGe shifted toward a lower wavenumber. Furthermore, the enhanced Raman spectrum was clearly attributed to not only the oil-immersion measurement but also the SERS effect. Fig. 3 shows the peak of strained SiGe obtained by the SERS measurement after the subtraction of the Si substrate peak from the raw data. Both TO and LO phonon components were clearly extracted in fig. 3. From these Raman shift values, the anisotropic biaxial stress can be calculated by the relationship between stress and Raman with the use of phonon deformation potentials (PDPs) and elastic compliances [4,5,6]. As a result, σxx = -2.13 and σyy= -2.21 GPa were obtained. From the results, it was confirmed that the TO phonon was able to be efficiently excited by the SERS. We concluded that the shift on the low wavenumber side was definitely attributed to the TO phonon excitation. The TO/LO phonon excitation allows us to evaluate anisotropic biaxial stress in thin strained-SiGe. Acknowledgement This study was partially supported by the Japan Society for the promotion of Science through a Grant-in-Aid for Scientific Research B (No. 24360125) and Funding program for World-Leading innovative R&D on Science and Technology.

Influence of Au Nanoparticle Surface Decoration on Highly Oriented SnO2 Nanorods/ZnO Hybrid Films for Gas Sensing Improved Performance

Hybrid films containing SnO2 nanorods and ZnO michrorods were grown by a low-temperature vapor-liquid-solid (VLS) technique. Au nanoparticle decoration on the SnO2 and ZnO structures was succesfully carried out simultaneously by using a UV wavelength light source and a simple bath solution of HAuCl4·4H2O in ethanol. Surface morphologies and structural properties of the Au decorated SnO2 & ZnO structures were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The Au decorating nanoparticles were found to be 10nm in average size showing an even dispersion along the hybrid films. Average sizes of the SnO2 nanorods and ZnO michrorods were reported previously elsewhere. Gas sensing measurements for acetone vapor, ethanol vapor, and carbon monoxide were carried out and compared using three different transducer films consisting in pure SnO2 film, undecorated SnO2 & ZnO hybrid film, and Au decorated SnO2 & ZnO hybrid film. Surface area and Au decoration dramatically influence the sensing device performance and this features are discussed in the present work.

Wavefront watermarking of technical and biological samples using digital random phase modulation and phase retrieval

A technique for digital watermarking of smooth object wavefronts using digital random phase modulation and multiple-plane iterative phase retrieval is demonstrated experimentally. A complex-valued watermark is first encrypted using two random phase masks of known distributions before being superposed onto a set of host wavefront intensity patterns. Encryption scaling factor and depth of randomization of the masks are optimized such that the amplitude and phase watermarks are decrypted successfully and are not distorting the host wavefront. Given that the watermarked intensity patterns and the numerous decryption keys are available (i.e. distances between recording planes, light source wavelength, pixel size, random phase masks and their distances to the planes are all known), increasing the number of watermarked patterns used results in enhanced quality of decrypted watermarks. The main advantage of wavefront watermarking via the phase retrieval approach compared to the holographic approach is the avoidance of reference wave-induced aberration. Watermarking of wavefronts from lenses and unstained human cheek cells demonstrate the effectiveness of the technique.

Research of multiple wavelength light source based on super-continuous spectrum

In order to meet the requirements of the multi-wavelength light source of large-capacity, high-speed, long-distance optical communication system, we researched the multi-wavelength light source based on super-continuum (SC), analyzed the main factors in the SC generation, such as dispersion, nonlinear effects. The SC simulation and optimization around the input pulse width, peak power, fiber length, non-linear coefficient parameters for analysis. The optimized results: SC input achieved 25GHz repetition rate, amplified by high power EDFA, input average power did not exceed 33dBm. The output of the SC 3dB bandwidth was greater than 70nm, after AWG, output 320 wavelengths, wavelength spacing is 0.2nm (25GHz), the signal-to-noise ratio was greater than 30dB.

Detection of Gunshot Residue on Dark‐Colored Clothing Prior to Chemical Analysis

Detection of gunshot residue (GSR) is an arduous task for investigators. It is often accomplished with chemical tests, which can reveal elements and ions indicating the presence of GSR, but are likely to cause physical alteration to the pattern. In this study, the Spex Forensics Mini-CrimeScope MCS 400, along with 16 accompanying wavelength filters, was applied to various GSR patterns and target types. Three dark shirt materials, four ammunition calibers, and eight ammunition manufacturers, along with the primer residue of the different manufacturer ammunitions were tested. Results indicate the alternate light source wavelength of 445 nm to be the optimal setting. In addition, target material plays a large role in the preservation of GSR patterns as particles burn. Furthermore, it can be extrapolated that residue, observed from a full round and firing distance of six inches, is mostly composed of unburnt gunpowder residue, not primer residue.

Effect of post deposition by UV irradiation on chemical bath deposited tin sulfide thin films

Tin sulfide thin films have been grown on glass substrates by chemical bath deposition technique (CBD) at room temperature and irradiated with UV light source of wavelength 355 nm. The effect of UV illumination on the physical properties of the films was compared with that of the as-prepared film. Though the thickness of the films was unaltered after illumination, the structural, optical and electrical properties changed considerably. Structural studies showed the polycrystalline nature of the UV-illuminated sample, whereas the as-prepared film was mono crystalline. Both films were orthorhombic structure with Sn2S3 phase. The optical properties of the films were systematically studied using the optical absorbance and reflection spectra. Studies on the reflection spectra showed higher reflectance in visible and infrared region for the UV-illuminated films and lower reflectance in the infrared region for the as-prepared one. The variation of the refractive index of the samples was also analyzed. The optical absorption coefficient and the optical band gap energy of the films were evaluated. The irradiated film exhibited lower band gap of 1.74 eV than the value of as-prepared film, i.e., 1.77 eV. The measured resistivity of the tin sulfide thin films was found to be of the order of 108 and 109 Ωcm for UV-illuminated and as-prepared films, respectively. The SEM images showed the presence of worm-like nanostructures with almost similar appearance in both the films.

一种差分吸收式光纤瓦斯传感系统

Optical fiber methane gas sensing system based on differential absorption was investigated. Two distributed feedback laser diodes were used in the system.The wavelength of the reference light source was 1551nm and the wavelength of the measurement light source was 1653nm,which was located around the absorption peak wavelength of methane.The methane absorption peak was detected by scanning the wavelength of the measurement light source,and then the concentration of methane was measured by comparing the output power at the absorption peak with that not at the absorption band. The system possesses the properties of high resolution,good stability and a measurement resolution of 0. 038%is achieved for methane detection.

Crystalline undulator radiation and motion behavior in the vicinity of the resonance line

Searching for new light source, especially short wave-length coherence light source has attracted extensive attention. The using of the crystalline undulator radiation as a short wave-length coherence light source is most likely to be one of the options. From the viewpoints of potential and field, the centrifugal force generated by periodic bent crystal is regarded as centrifugal potential, the particle motion equation is reduced to Mathieu equation with Duffing-type, and from the energy viewpoint the stability of the system is discussed. The behaviors of particles in the vicinity of the resonance are analyzed by perturbation method; the jump phenomena and instable behavior are revealed. The results show that the stability of the system is related to its parameters, and only properly adjusting these parameters, the bifurcation and instability for the system can be avoided in principle.