The effects of temperature on different laser transitions of neodymium orthovanadate crystal

The temperature dependence of Nd:YVO4 laser crystal pumped by laser diode emitting at 808 nm is studied within the range of 5 °C to 60 °C. The spectroscopy properties of quasi three level at 914 nm (4F3/2 -4I9/2) and four level at 1064 nm (4F3/2 -4I11/2) are characterized. The lineshape function of the transition lines were broadened as the temperature increases. The phenomenon is attributed to change in linewidth, lineshift and intensity. The linewidths for both laser transition of 914 nm and 1064 nm increases with temperature with the rate of 0.105 cm-1/°C and 0.074 cm-1/°C respectively. The peak of 914nm and 1064 nm lineshapes shifted to a longer wavelength with the rate of 3.0 pm/°C and 4.2 pm/°C respectively which correspond to same amount of lineshift. The lineshape broadening with respect to the temperature is due to one-phonon emission and Raman phonon scattering processes. The intensities of 914 nm and 1064 nm transition lines are found to be decreased at the rate of 0.15 %/°C and 0.45 %/°C respectively due to non-radiative effects. Quasi three level laser transition is more temperature dependent because it terminal level is close to the ground state which suffers from higher phonon-ion interaction rather than four level laser system

Weighing the galactic disc using the Jeans equation: lessons from simulations

Using three-dimensional stellar kinematic data from simulated galaxies, we examine the efficacy of a Jeans equation analysis in reconstructing the total disk surface density, including the dark matter, at the ‘Solar’ radius. Our simulation data set includes galaxies formed in a cosmological context using state-of-the-art high-resolution cosmological zoom simulations, and other idealized models. The cosmologically formed galaxies have been demonstrated to lie on many of the observed scaling relations for late-type spirals, and thus offer an interesting surrogate for real galaxies with the obvious advantage that all the kinematical data are known perfectly. We show that the vertical velocity dispersion is typically the dominant kinematic quantity in the analysis, and that the traditional method of using only the vertical force is reasonably effective at low heights above the disk plane. At higher heights the inclusion of the radial force becomes increasingly important. We also show that the method is sensitive to uncertainties in the measured disk parameters, particularly the scalelengths of the assumed double exponential density distribution, and the scalelength of the radial velocity dispersion. In addition, we show that disk structure and low number statistics can lead to significant errors in the calculated surface densities. Finally, we examine the implications of our results for previous studies of this sort, suggesting that more accurate measurements of the scalelengths may help reconcile conflicting estimates of the local dark matter density in the literature

Structural and optical properties of surfactant assisted SiO2-TiO2 hybrid matrix for pH sensing: sol-gel approach

Structural and optical properties of surfactant-assisted SiO2-TiO2 hybrid matrix as a highly responsive optical sensing material by sol-gel method are investigated. Microscopic results indicate the uniform morphology with large pores without any cracks. Matrices have a high surface area (489–342 m2/g), which has more capability to sense the broader pH range. From UV–visible spectroscopy, it is found that after encapsulation, matrix has ~ 78 % optical transparency with low refractive index of 1.44 corresponding to thickness 138.7 nm. Sensing analysis revealed that the prepared coating has good sensitivity at pH 12 and fast response time. Low refractive index and highly porous matrix, combined for achieving a good responsive optical chemical sensors. This research also opens an aveanue for ths material to be considered as a functional coating

The effect of laser irradiation on the viability of human breast cancer cell, MDA-MB-231

A practical pass-through type fibre Bragg grating (FBG) temperature sensor system have been designed, developed, simulated, and experimentally investigated. The performance of FBG was evaluated in harsh environments exposed under direct sunlight, rain, and wind. The sensor system designed directly focused with convex and hand lens. The temperature of FBG’s sensor head been measured. The broadband laser source was launched into the system using tunable laser source (TLS) and both transmission and reflection spectra of FBG sensor were measured by optical spectrum analyzer (OSA). Results shows that the Bragg wavelength shift, ΔλB increased proportionally with the temperature changes. The sensitivity of FBG were recorded at 0.0100 and 0.0132 nm °C-1 for the systems where convex and hand lens applied to the FBG’s sensor head respectively, while the sensitivity of 0.0118 nm °C-1 measured for the system without any focusing element applied

Nanostructural and optical properties of hierarchical ZnO grown via hydrothermal method

A simple hydrothermal method was employed to synthesize 3D hierarchical ZnO nanorods deposited on Si (100) substrate at different growth temperatures (110 and 90oC) within 3 h. The structure, mode and composition of hierarchical ZnO nanorods were investigated by XRD, FESEM and EDX spectroscopy. The polycrystalline ZnO nanostructures products were indexed as hexagonal wurtzite structured, while the morphology was urchin like ZnO nanorods with different aspect ratio of nanorods and stoichiometric. The photoluminescence (PL) properties were studied of as-grown ZnO samples dependent on various growth temperatures. The PL results after UV excitation source were shown a single broad Vis emission peak for both samples with absents of UV emission peak. The emission edge of Vis peak was exhibited blue-shift due to increase temperature growth, and that suggest enhancement in hierarchical ZnO nanorods crystallinity. Oxygen deficiency is evidence on the creation various defects types in hierarchical ZnO nanorods. It is responsible on Vis emission bands. The results demonstrate promising future for the hierarchal ZnO nanostructure which could be applied in optoelectronics and gas sensing

Laser tattoo removal comparison between 1064 and 532 NM of a Q-switched ND:YAG laser treatment

Invention of the Q-switch advanced laser method is the most effective methods of tattoo removal compared to other methods of i.e. chemical, mechanical and surgical. In this study, we are reporting black pigment tattoo removal by comparing two wavelengths 532 nm and 1064 nm of Q-switched Nd-YAG laser. Using a single-pulse laser at 1064 nm wavelength, the maximum laser fluence for skin damage is 3.04 J/cm2 with pulse energy 0.55 J. While, at 532 nm wavelength, maximum laser fluence is 0.5 J/cm2 with pulse energy 0.42 J at 8-10 ns for tattooed skins. Moreover, after 1064 nm and 532 nm laser irradiations, skin biopsy of black tattooed rat’s skin demonstrates the ink granules local redistribution. Microscopic study indicates that black ink particles become smaller and vanished from the skins after 1064 nm laser treatment. The findings of this study indicate that 1064 nm wavelengths of Q-switched Nd-YAG laser treatment with 0.55 J pulse energy, is one of the significant methods of black tattoo removal with remarkable differences

Synthesize of gold nanoparticles with 532 NM and 1064 NM pulse laser ablation

The effect of laser wavelength on gold nanoparticle fabrication is reported. Colloidal solutions of gold nanoparticles were prepared by pulsed laser ablation technique in deionized water. A Q-switched Nd:YAG laser with constant energy of 65mJ and operation at fundamental wavelength and second harmonic generation was utilized as a source of energy. Fabricated particles were characterized by using Smart Nanoparticles Measurements (SNM) system. The average diameters of gold nanoparticles achieved as19 nm and 12 nm corresponding to 1064 nm and 532 nm respectively. The fragmentation of colloidal particles by self-absorption of laser pulses is the responsible mechanism to cause for reduction

Hydrogen production by infrared laser electrolysis on NaCl solution

A method referred as Hydrogen Production by Infrared assisted Electrolysis (HyPIR) is presented in this work. Two graphite electrodes are immersed in electrolytic cell containing 0.517 g of NaCl and 7 ml of ethanol C2H5OH solution which act as supplements for a partial oxidation reaction. Erbium YAG laser with wavelength of 2.94 mm and 57.6 mJ energy per pulse at a pulse rate of 4 Hz is illuminated directly on the electrolytic solution. The irradiating light facilitates the dissociation of water by stretching the inter-atomic hydrogen-oxygen bonds in the electrolytic solutions and directly increase the rate of hydrogen yields

Analyses for various doping structures of SOI-based optical phasemodulator using free carrier dispersion effectB

tThis paper highlights the study on various structure of silicon-on-insulator (SOI) optical phase modula-tors based on free carrier dispersion effect. The proposed modulators employ the forward biased P-I-Ndiode structure integrated in the waveguide and will be working at 1.55 m optical telecommunicationswavelength. Three kinds of structure are compared systematically where the p+ and n+ doping positionsare varied. The modeling and characterization of the SOI phase modulators was carried out by 3D numer-ical simulation package. Our results show that the position of doping regions have a great influences tothe device performance. It was discovered that the best structure in this work demonstrated modulationefficiency of 0.015 V cm with a length of 155 m

The effects of the ambient liquid medium on the ablation efficiency, size and stability of silver nanoparticles prepared by pulse laser ablation in liquid technique

Silver (Ag) nanoparticles (NPs) were synthesized by pulsed laser (Nd:YAG, 1064 nm) ablation of individual target in various solutions. The influence of deionized water (DIW), ethanol and Polyvinylpyrrolidone (PVP) as ambient medium on the fundamental aspects such as ablation efficiency, particle size and stability of Ag NPs was studied. UV-vis spectrophotometer and transmission electron microscopy (TEM) were used to study the optical characterization and morphological analysis of all the synthesized samples, respectively. Preparation in DIW was carried out as a reference sample. The experiments demonstrated that ablation efficiency and stability of NPs in ethanol medium are lowest than those prepared in PVP medium and the reference sample. PVP medium led to higher stability, lower ablation efficiency and finer average particle size compared to reference sample