Multiphoton absorption in CsLiB6O10 with femtosecond infrared laser pulses

Nonlinear absorption and refraction characteristics of cesium lithium borate (CsLiB6O10) crystal have been studied using Z-scan technique. Ti:sapphire laser with 110 fs pulse width operating at 800 nm wavelength and pulse repetition rate of 1 kHz is used as the source of photons. Intensity of the laser pulse is varied from 0.541 to 1.283 T W/cm2 to estimate the intensity dependence of multiphoton absorption coefficients. Using the theory of multiphoton absorption proposed by Sutherland [ Handbook of Nonlinear Optics, in 2nd ed., edited by D. G. McLean and S. Kirkpatrick, Dekker, New York (2003) ], found that open aperture Z-scan data fit well for the five-photon absorption (5PA) process. 5PA coefficients are obtained by fitting the expressions into the open aperture experimental data for various peak intensities (I00). The nonlinear refractive index n2 estimated from closed aperture Z-scan experiment is 1.075×10−4 cm2/T W at an input peak intensity of 0.723 T W/cm2. The above experiment when repeated with a 532 nm, 6 ns pulsed laser led to an irreversible damage of the sample resulting in an asymmetric open aperture Z-scan profile. This indicates that it is not possible to observe multiphoton absorption in this regime of pulse width using 532 nm laser.

Real source-sink pair

This work is concerned with the interaction of a source-sink pair. The main parameters of the problem are source and sink flow rates, the axial and lateral separations of the source and sink, and the angle between the axes of source and sink. Of concern is the percentage of source fluid that enters the sink as a function of these parameters. The experiments have been carried using the source nozzle diameter of 6 mm and the sink pipe diameter of two sizes: 10 mm and 20 mm. The Reynolds numbers of the source jet is about 3200. The main diagnostics are flow visualization using dye, laser induced fluorescence (LIF), particle streak photographs and particle image velocimetry (Ply). To obtain the removal effectiveness (that is percentage of source fluid that is going through the sink pipe), titration method is used. The sink diameter and the angle between source and the sink axes do not influence efficiencies as do the sink flow rate and the lateral separation. Data from experiments have been consolidated so that these results can be used for designing sinks for removal of heat and pollutants. (C) 2011 Elsevier Ltd. All rights reserved.

Foot-mounted INS for everybody - an open-source embedded implementation

We present an open-source, realtime, embedded implementation of a foot-mounted, zero-velocity-update-aided inertial navigation system. The implementation includes both hardware design and software, uses off-the-shelf components and assembly methods, and features a standard USB interface. The software is written in C and can easily be modified to run user implemented algorithms. The hardware design and the software are released under permissive open-source licenses and production files, source code, documentation, and further resources are available at www.openshoe.org. The reproduction cost for a single unit is below $800, with the inertial measurement unit making up the bulk ($700). The form factor of the implementation is small enough for it to be integrated in the sole of a shoe. A performance evaluation of the system shows a position errors for short trajectories (<;100 [m]) of ± 0.2-1% of the traveled distance, depending on the shape of trajectory.

Visualization of coherent structures in turbulent subsonic jet using planar laser induced fluorescence of acetone

In this paper, we present the molecular density distribution measurement in turbulent nitrogen jet (Re approximate to 3 x 10(3)), using acetone as molecular tracer. The tracer was seeded in the nitrogen jet by purging through the liquid acetone at ambient temperature. Planar laser sheet of 266 nm wavelength from frequency quadrupled, Q-switched, Nd:YAG laser was used as an excitation source. Emitted fluorescence images of jet flow field were recorded on CMOS camera. The dependence of planar laser induced fluorescence (PLIF) intensity on acetone vapor density was used to convert PLIF image of nitrogen jet into the density image on pixel-by-pixel basis. Instantaneous quantitative density image of nitrogen jet, seeded with acetone, was obtained. The arrowhead-shaped coherent turbulent structures were observed in the present work. It was found that coherent structures were non-overlapping with separate boundaries. Breaking of coherent structures into turbulence was clearly observed above four times jet width.

Facile synthesis of carbon doped TiO2 nanowires without an external carbon source and their opto-electronic properties

The present study demonstrates a simple protocol for the preparation of one dimensional (1D) oxidized titanium carbide nanowires and their opto-electronic properties. The oxidized titanium carbide nanowires (Ox-TiC-NW) are prepared from TiC nanowires (TiC-NW) that are in turn synthesized from micron sized TiC particles using the solvothermal technique. The Ox-TiC-NW is characterized by X-ray diffraction, UV-Vis spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Raman spectroscopy. Thermal oxidation of TiC-NW yields carbon doped TiO2-NW (C-TiO2-NW), a simple methodology to obtain 1D C-TiO2-NW. Temperature dependent Raman spectra reveal characteristic bands for TiO2-NW. Electrical characterization of individual C-TiO2-NW is performed by fabricating a device structure using the focused ion beam deposition technique. The opto-electronic properties of individual C-TiO2-NW demonstrate visible light activity and the parameters obtained from photoconductivity measurements reveal very good sensitivity. This methodology opens up the possibility of using C-TiO2-NW in electronic and opto-electronic device applications.

Intense Acoustic Burst Ultrasound Modulated Optical Tomography for Elasticity Mapping of Soft Biological Tissue Mimicking Phantom: A Laser Speckle Contrast Analysis Study

This report addresses the assessment of variation in elastic property of soft biological tissues non-invasively using laser speckle contrast measurement. The experimental as well as the numerical (Monte-Carlo simulation) studies are carried out. In this an intense acoustic burst of ultrasound (an acoustic pulse with high power within standard safety limits), instead of continuous wave, is employed to induce large modulation of the tissue materials in the ultrasound insonified region of interest (ROI) and it results to enhance the strength of the ultrasound modulated optical signal in ultrasound modulated optical tomography (UMOT) system. The intensity fluctuation of speckle patterns formed by interference of light scattered (while traversing through tissue medium) is characterized by the motion of scattering sites. The displacement of scattering particles is inversely related to the elastic property of the tissue. We study the feasibility of laser speckle contrast analysis (LSCA) technique to reconstruct a map of the elastic property of a soft tissue-mimicking phantom. We employ source synchronized parallel speckle detection scheme to (experimentally) measure the speckle contrast from the light traversing through ultrasound (US) insonified tissue-mimicking phantom. The measured relative image contrast (the ratio of the difference of the maximum and the minimum values to the maximum value) for intense acoustic burst is 86.44 % in comparison to 67.28 % for continuous wave excitation of ultrasound. We also present 1-D and 2-D image of speckle contrast which is the representative of elastic property distribution.