Search results for "laser"
showing 10 items of 3161 documents
Polarized multiplex coherent anti-Stokes Raman scattering using a picosecond laser and a fiber supercontinuum
2011
International audience; We perform multiplex coherent anti-Stokes Raman scattering (CARS) micro-spectroscopy with a picosecond pulsed laser and a broadband supercontinuum (SC) generated in photonic crystal fiber. CARS signal stability is achieved using an active fiber coupler that avoids thermal and mechanical drifts. We obtain multiplex CARS spectra for test liquids in the 600–2000 cm−1 spectral range. In addition we investigate the polarization dependence of the CARS spectra when rotating the pump beam linear polarization state relative to the linearly polarized broad stokes SC. From these polarization measurements we deduce the Raman depolarization ratio, the resonant versus nonresonant …
Physical-mechanical effects of Nd:YAG laser on the surface of sound dental enamel.
1993
Human dental enamel samples were irradiated using a 5 kHz Q-Switched Nd:YAG laser. An increase in Knoop microhardness and modification of the membrane permselectivity were detached. These results and the changes observed by SEM, can be connected with the fusion of the enamel surface.
Optical field-induced surface-relief micropatterning of amorphous chalcogenide thin films
2015
The study of direct recording of the surface relief gratings on amorphous chalcogenide thin (2.5 to 5 μm films is presented by three different recording setups. Recording was performed on As2S3 by 532-nm wavelength laser light. Additionally, the evolution of a surface relief in dependence from the recording time and polarization has been investigated in detail and for the first time, the mass transfer process has been explained from the point of view of the photoinduced birefringence. The role of photoinduced plasticity in the formation of surface relief in amorphous chalcogenides during holographic recording has been discussed.
Programmable color tuning of a multiline laser by means of a twisted nematic liquid crystal display.
2012
An optical system useful to tune in a controlled way the color of a triline argon krypton (Ar–Kr) laser by means of a twisted nematic liquid crystal display (TNLCD) is presented. The optical setup employs a 4f system and two blazed gratings to first separate and then recombine the spectrum of the light beam. The TNLCD is included in the intermediate focal plane operating in the amplitude modulation mode to control the relative transmission of each spectral line. The resulting color is accurately predicted by using a previously developed physical model of the spectral and voltage dependence of the TNLCD birefringence. By simply changing the gray level image addressed to the display, the Ar–K…
Tunability of Injection Seeded High-Repetition Rate Ti:Sapphire Laser Far Off the Gain Peak
2009
We have investigated a tunability of a high‐repetition rate Ti:Sapphire laser seeded off the gain peak. By applying a birefringent filter, the 7 kHz injection seeded Ti:Sapphire laser system was operated with the average seeding efficiency of over 90% and the output power of over 1 W on the spectral range of 900–930 nm. We conclude that the birefringent filter suited for widely tunable operation of the injection seeded Ti:Sapphire laser system operated at high repetition rate.
Pulsed-laser switching in the bistability domain of a cooperative spin crossover compound: a critical study through calorimetry
2015
The photoswitching from the low spin (LS) to high spin (HS) state and the reverse process in the bistability domain of spin crossover (SCO) compounds is a promising function to be used in molecular electronic devices, and evidenced mainly through spectroscopy. The phenomenon, and in particular its mechanism, is however still under debate since some controversial experimental results have been reported. Here we present a calorimetric experimental study of the photoswitching of the [Fe(pyrazine)Pt(CN)4] SCO material by a nanosecond-pulsed green laser. Our results confirm that the single laser pulse of varying energies results in significant LS to HS transformations and show that calorimetry p…
Repair bond strength of composite : effect of surface treatment and type of composite
2017
Background By an increase in use of composite restorations, some defects are also seen in these restorations, which need to be repaired. Since complete replacement of an old restoration may compromise the tooth structure, repair of defect is a more practical approach if there is no caries recurrence. Risk of pulp injury also decreases as such. One major challenge in restoration repair is to obtain a durable bond between the new and old composite. Laser irradiation has been suggested for surface preparation of old composite. This study aimed to assess the effect of composite surface preparation with Er,Cr:YSGG laser on microtensile bond strength to new composite. Material and methods A total…
The effect of surface treatment with Er: YAG laser on shear bond strength of orthodontic brackets to fiber-reinforced composite
2014
Objectives: This study aimed to investigate the effect of surface treatment with Er:YAG laser on shear bond strength (SBS) of orthodontic brackets to fiber-reinforced composite (FRC). Study Design: Ninety human premolars were randomly divided into six groups of 15. FRC bars were bonded to the teeth with a flowable composite (FC) and then underwent following treatments. In group 1 no further treatment was performed. In group 2 the FRC surfaces were covered by FC. An Er:YAG laser was employed to treat FRCs in groups 3 ( 200 mJ/10 Hz) and 4 (300 mJ/15 Hz). The FRC strips in groups 5 and 6 were first covered by FC and then irradiated with Er:YAG laser at 200 mJ/10 Hz (group 5) or 300 mJ/15 Hz (…
Laser-induced plasma spectroscopy to as low as 130 nm when a gas-purged spectrograph and ICCD detection are used.
2003
An experimental setup is described for measuring laser-induced plasma emission spectra in the near vacuum UV with a Czerny-Turner spectrograph and intensified charge-coupled device under atmospheric pressure. With a simple gas-purge technique, emission lines down to 130 nm could be recorded. The strongest emission lines of bromine, chlorine, and iodine in the near vacuum UV are easily detected.
Optical non-contact electric field mapping by LIF in Cs vapor
2007
We present experimental and theoretical studies of the possibility of using cesium vapor as a tracer gas for optical non-contact electric field mapping. Optical images of electric field distributions have been obtained.