JEOS:RP - Journal of the European Optical Society Rapid publications
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Improving the polishing accuracy by determining the variance of the friction coefficient
Get PDFThe variation of the friction coefficient in the polishing process is investigated comparing the results of a numerical simulation with polishing experiments. To improve the accuracy of the predicted wear in the simulation a method is presented to measure the friction coefficient in relation to the relative velocity using an offset tool
Thermal diffusivity measurement of copper nanofluid using pulsed laser thermal lens technique
Get PDFThe pulsed laser thermal lens technique was used to study the thermal diffusivity of fluids containing copper nanoparticles (Cu-NPs) prepared by γ-irradiation method. The samples were prepared for the different concentrations of Cu precursor at 20 KGy dose. A Q-switched Nd-YAG pulsed laser of wavelength 532 nm was used as an excitation source and He-Ne laser was used as a probe beam in the present thermal lens experiment. It was found that the thermal diffusivity of the solution depends on the density of Cu-NPs
Synthesis, characterization and nonlinear optical properties of silver/PVA nanocomposites
Get PDFSilver/polyvinyl alcohol (PVA) nanocomposites are prepared via quick precipitation method, using hydrazine as a reducing agent. Preparing of silver/PVA nanocomposites by this method is done for the first time. The samples are characterized by Uv-Visible spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM). Nonlinear optical properties are carried out by Z-scan technique using a blue CW laser beam operated at wavelength 405 nm. It is shown that the synthesized samples have negative nonlinear refractive index and the magnitude is in the order of 10^-8. The nonlinear refractive index increases as amount of reducing agent increases
Diffractive and interferometric methods to characterize photopolymers with liquid crystal molecules as holographic recording material
Get PDFWe present two methods, interferometry at the zero spatial frequency limit and analysis of diffracted orders for very low spatial frequency gratings, to characterize photopolymers with dispersed nematic liquid crystals. These methods provide us with real time information about the transformations taking place inside the material during recording
Microlens array production in a microtechnological dry etch and reflow process for display applications
Get PDFThe fabrication of arrays consisting of densely ordered circular convex microlenses with diameters of 126 μm made of quartz glass in a photoresist reflow and dry etch structure transition process is demonstrated. The rectangular lens arrays with dimensions of 6 mm x 9 mm were designed for focussing collimated light on the pixel center regions of a translucent interference display, which also was produced in microtechnological process steps. The lenses focus light on pixel centers and thus serve for increasing display brightness and contrast since incoming collimated light is partially blocked by opaque metallic ring contacts at the display pixel edges. The focal lengths of the lenses lie between 0.46 mm and 2.53 mm and were adjusted by varying ratio of the selective dry etch rate of photoresist and quartz glass. Due to volume shrinking and edge line pinning of the photoresist structures the lenses curvatures emerge hyperbolic, leading to improved focussing performance
Fabrication of low-loss SOI nano-waveguides including BEOL processes for nonlinear applications
Get PDFWe report successful fabrication of low-loss SOI nano-waveguides with integrated PIN diode structures. The entire fabrication process is done on a 200 mm BiCMOS toolset using front-end-of-line (FEOL) and back-end-of-line (BEOL) processes and does not show any undesirable influence upon the photonic performance. Such a waveguide technology forms an attractive platform for a wide range of nonlinear applications due to efficient free carrier removal as well as use of standard substrates and processing technology. Nonlinear experiments were conducted to investigate the potential of the introduced technology. The performance of the designed waveguides can be used as a benchmark for future development of proposed platform for integrated silicon photonics and electronics circuits
Light scattering measurements for quantifying biological cell concentration: an optimization of opto-geometric parameters
Get PDFAn experimental study was carried out, aimed at optimizing the optical/geometrical configuration for measuring the concentration of biological cells by means of static light scattering measurements. A LED-based optoelectronic setup making use of optical fibers was experimented, as the precursor of a low-cost device to be integrated in instrumentation for cytometry. Two biological sample types were considered as test samples of the most popular analyses – cervical cells and urine, respectively. The most suitable wavelengths and detecting angles were identified, and calibration curves were calculated
Tuning the focal point of a plasmonic lens by nematic liquid crystal
Get PDFA theoretical and numerical investigation of tunable plasmonic nano-optic lens on the basis of liquid crystal are proposed as a new method of active modulating the output beam. The focal length can be controlled easily by exposing plasmonic nano-optic lens to constant external electric field. The physical principle of this phenomenon is evaluated from the phase of Fabry-Perot (F-P) resonance in slits and electro-optical effect of liquid crystal. Our numerical simulations reveal that large tuning range of the focal length up to 725 nm can be achieved. The results in this article provide a potential way to realize tunable plasmonic lens, which can be applied as an efficient element in ultrahigh nano-scale integrated photonic circuits for miniaturization and tuning purposes
Method for arbitrary phase transformation by a slab based on transformation optics and the principle of equal optical path
Get PDFThe optical path lengths travelled by rays across a wavefront essentially determine the resulting phase front irrespective of the shape of a medium according to the principle of equal optical path. Thereupon we propose a method for the transformation between two arbitrary wavefronts by a slab, i.e. the profile of the spatial separation between the two wavefronts is taken to be transformed to a plane surface. Interestingly, for the mutual conversion between planar and curved wavefronts, the method reduce to an inverse transformation method in which it is the reversed shape of the desired wavefront that is converted to a planar one. As an application, three kinds of phase transformation are realized and it is found that the transformation on phase is able to realize some important properties such as phase reversal or compensation, self focusing, and expanding or compressing beams, which are further confirmed by numerical simulations. The slab can be applied to realizing compact electromagnetic devices for which the values of the refractive index or the permittivity and permeability can be high or low, positive or negative, or near zero, depending on the choice of coordinate transformations
Sign Identification of Nonlinear Refractive Index of Colloidal Nanoparticles by Moiré Deflectometry Technique
Get PDFIn this paper, a visual rapid technique is presented for the sign identification of nonlinear refractive index of colloidal nanoparticles based on non-scanning Moiré deflectometry technique. In this method two lasers are used, one as a pump laser beam which causes thermal nonlinear effects in the sample and the second one is used as a probe beam laser which allows us to monitor these effects by Moiré deflectometry technique. The gradient of the nonlinear refractive index produced by the interaction of the pump laser, generates a cylindrical lens in the sample. The concave and convex lenses are produced as a result of negative and positive nonlinear refractive index respectively. Geometrical and experimental investigations show the Moiré fringes are deflected in two different directions by these lenses. By observing the shape of deflected moiré fringes, we can determine the sign of nonlinear refractive index and there will be no need for calibration or complicated calculations. This technique was applied for identification of nonlinear refractive index of Au and Tio_2 colloidal nanoparticles, under 47 mW second harmonic of Nd:YAG laser illumination. The sign of nonlinear refractive index of colloidal Au and Tio_2 nanoparticles were observed to be negative and positive respectively