Search results for "laser"

Influence of laser beam profile on the generation of ultrasonic waves

2011

The different ultrasonic fields generated in metallic materials by a laser beam with flat and Gaussian profile are investigated experimentally and using the finite element method (FEM). A high power laser beam irradiating a solid surface produces elastic waves with a mechanics that depends on many parameters, including the profile of the laser beam. The influence of the beam profile is investigated with the FEM analysis, considering the temperature dependence of material properties.

β-C3N4 Nanocrystals: Carbon Dots with Extraordinary Morphological, Structural, and Optical Homogeneity

2018

Carbon nanodots are known for their appealing optical properties, especially their intense fluorescence tunable in the visible range. However, they are often affected by considerable issues of optical and structural heterogeneity, which limit their optical performance and limit the practical possibility of applying these nanoparticles in several fields. Here we developed a synthesis method capable of producing a unique variety of carbon nanodots displaying an extremely high visible absorption strength (ε > 3 × 106 M(dot)−1 cm−1) and a high fluorescence quantum yield (73%). The high homogeneity of these dots reflects in many domains: morphological (narrow size distribution), structural (q…

Proton exchanged waveguides in LiNbO<inline-formula><sub>3</sub></inline-formula> and LiTaO<inline-formula><sub>3…

1998

High Voltage Metrology with Collinear Laser Spectroscopy

2018

We present results of laser spectroscopic high voltage measurements on the 5 ppm relative uncertainty level using a pump and probe scheme on Ca+ ions. With the two-stage laser interaction and with a reference measurement we can eliminate systematic effects like differences in contact potentials of electrode materials, thermo-electric voltages, and the unknown starting potential of the ions in the ion source. Our measurements are compatible with the 5 ppm precision limits of the high voltage dividers used for comparison and demonstrate an unprecedented increase in the accuracy of laser-based high voltage measurements by a factor of 20.

<title>Amorphous chalcogenide thin films as a media for holographic recording</title>

2004

The amorphous As2S3 and As40S15Se45 films as a recording media for optical holography and lithography were studied. The results on research of the transmission, surface-relief and Bragg reflection grating holographic recording and readout conditions are presented. The recording of transmission holographic gratings in As40S15Se45 films was performed by He-Ne (0.6328 μm) laser beam, while the redout of the diffraction efficiency was made at Bragg agle using diode (0.805 μm) laser lines. The Bragg reflection gratings in As2S3 films were recorded and studied by Ar+ laser line 0.5145 μm. The surface-relief modulated gratings with a period of 0.15 μm - 1 μm were recorded.© (2004) COPYRIGHT SPIE--…

Silicon germanium platform enabling mid-infrared to near-infrared conversion for telecom and sensing applications

2014

This paper presents the potential of silicon germanium waveguides in the nonlinear conversion of light from mid-infrared wavelengths to the telecom band utilizing four-wave mixing. Design aspects and first characterization results of fabricated devices are presented.

Imaging of Laser-Excited Autofluorescence Fading Rates: Novel Technique for Tissue Surface Structure Studies

2008

Experimental methodology for imaging of laser-excited tissue autofluorescence fading rates has been developed and clinically tested. Details of the equipment and image processing are described, along with measurement results confirming feasibility of the novel technology.

Erratum to “Using Infrared thermography in order to compare laser and hybrid (laser+MIG) welding processes” [Optics & Laser Technology 41 (2009) …

2010

Erratum to ‘‘Using Infrared thermography in order to compare laser and hybrid (laser+MIG) welding processes’’ [Optics & Laser Technology 41 (2009) 665–670] Simone Mattei a, , Dominique Grevey , Alexandre Mathieu , Laetitia Kirchner b a Institut Carnot de Bourgogne,UMR5209 CNRS-Universite0 de Bourgogne, IUT Le Creusot, 12 rue de la Fonderie, 71200 Le Creusot, France b EADS France, 12 rue Pasteur, 91 152 Suresnes Cedex, France

Raman Studies of Photorefractive Lithium Niobate Single Crystals

2014

A study of Raman spectra of lithium niobate single crystals: stoichiometric, ostensibly pure congruent LiNbO3, and congruent LiNbO3 containing admixture of yttrium is reported. Raman bands observed in spectra excited by visible laser radiation are thoroughly compared to the same bands excited by infrared laser radiation. The broadening of Raman bands excited by radiation of shorter wavelengths is attributed to photo-refraction induced by visible radiation (514 nm) while being absent under infrared radiation (1064 nm). Attributing the effect of photo-refraction to radiation-induced structural changes in the illuminated part of the crystal lattice the authors interpret the observed broadening…

A compact and portable laser-induced breakdown spectroscopy instrument for single and double pulse applications

2008

Abstract We present LIBS experimental results that demonstrate the use of a newly developed, compact, versatile pulsed laser source in material analysis related to art and archaeological applications in view of research aiming at the development of portable LIBS instrumentation. LIBS qualitative analysis measurements were performed on various samples and objects, and the spectra were recorded in gated and non-gated modes. The latter is important because of advantages arising from size and cost reduction when using simple, compact spectrograph-CCD detection systems over the standard ICCD-based configurations. The new laser source exhibited a very reliable performance in terms of laser pulse …