Search results for "LASER"

A wideband THz Time Domain Spectroscopy system based on pulsed laser: model and experiments

2014

Effect of thermal annealing on the luminescence of defective ZnO nanoparticles synthesized by pulsed laser ablation in water

2016

This work concerns ZnO nanoparticles (NPs), with sizes of tens of nm, produced by ablation with a pulsed Nd:YAG laser of a Zn plate in H2O. TEM images evidence the formation of nanoparticles with sizes of tens of nm. Moreover, HRTEM images and Raman spectra show that the distance between the crystalline planes and the vibrational modes are consistent with ZnO nanocrystal in wurtzite structure. Their optical properties are characterized by two emission bands both excited above the energy gap (3.4 eV): the first at 3.3 eV is associated with excitons recombination, the second at 2.2 eV is proposed to originate from a singly ionized oxygen vacancy. The green emission is independent of water pH,…

Laser fluence, repetition rate and pulse duration effects on paint ablation

2006

Abstract The efficiency (mm3/(J pulse)) of laser ablation of paint was investigated with nanosecond pulsed Nd:YAG lasers (λ = 532 nm) as a function of the following laser beam parameters: pulse repetition rate (1–10,000 Hz), laser fluence (0.1–5 J/cm2) and pulse duration (5 ns and 100 ns). In our study, the best ablation efficiency (η ≅ 0.3 mm3/J) was obtained with the highest repetition rate (10 kHz) at the fluence F = 1.5 J/cm2. This ablation efficiency can be associated with heat accumulation at high repetition rate, which leads to the ablation threshold decrease. Despite the low thermal diffusivity and the low optical absorption of the paint (thermal confinement regime), the ablation th…

Luminescent Silicon nanocrystals produced by ns pulsed laser ablation

2013

The reduction of Si down to nanoscale introduces a peculiar visible luminescence, surprisingly for a not highly emissive material. This feature is relevant in connection with several application fields (optoelectronics, medicine) and has lead the research towards the development of production methods successful to control the physical and chemical properties of the nanosized Si so as to enhance and tune the luminescence. To this purpose, the laser ablation in liquids is particularly promising since it provides effective controlling parameters (laser photon energy, fluence, repetition rate, liquid reactivity) for the morphology and the structure of Si-related products. Here we report a study…

High-quality superconducting titanium nitride thin film growth using infra-red pulsed laser deposition

2018

Superconducting titanium nitride (TiN) thin films were deposited on magnesium oxide, sapphire and silicon nitride substrates at 700 °C, using a pulsed laser deposition (PLD) technique, where infrared (1064 nm) pulses from a solid-state laser were used for the ablation from a titanium target in a nitrogen atmosphere. Structural studies performed with x-ray diffraction showed the best epitaxial crystallinity for films deposited on MgO. In the best films, superconducting transition temperatures, T C, as high as 4.8 K were observed, higher than in most previous superconducting TiN thin films deposited with reactive sputtering. A room temperature resistivity down to ~17 μΩ cm and residual resist…

X-ray microtomography and laser ablation in the analysis of ink distribution in coated paper

2015

A novel method was developed for studying the ink-paper interface and the structural variations of a deposited layer of ink. Combining high-resolution x-ray tomography with laser ablation, the depth profile of ink (toner), i.e., its varying thickness, could be determined in a paper substrate. X-ray tomography was used to produce the 3D structure of paper with about 1 lm spatial resolution. Laser ablation combined with optical imaging was used to produce the 3D structure of the printed layer of ink on top of that paper with about 70 nm depth resolution. Ablation depth was calibrated with an optical profilometer. It can be concluded that a toner layer on a light-weight-coated paper substrate …

Confocal laser scanning microscopy for the study of the morphological changes of the postextraction sites

2012

A better understanding of the remodeling process of postextraction sockets is essential in dental treatment planning. The aim of this study was to evaluate whether confocal laser scanning microscopy (CLSM) can be applied to imaging contour changes of postextraction sites, as well as to its quantification with image analysis of obtained three-dimensional images. This work describes a new application of the CLSM technique. The system used was the OLS3100-USS, LEXT model (Olympus((R))). CLSM was used for the surface analysis of the extraction site. The measurements taken with CLSM were: (1) mesio-distal distance, (2) alveolar ridge thickness, and (3) vestibular and lingual alveolar ridge heigh…

Immediate dental implant placement in post-extraction-infected sites decontaminated with Er,Cr:YSGG laser: a retrospective cohort study

2022

Antecedentes científicos y objetivos de estudio La técnica quirúrgica para la colocación inmediata de un implante dental en un alvéolo post-extracción fue propuesta inicialmente en 1976 por Schulte y Heimke. La colocación de implantes dentales en alveolos post-extracción ofrece ventajas tales como un tiempo de tratamiento reducido y una mayor comodidad para el paciente; además esta técnica permite reducir la exposición quirúrgica del paciente y limitar la reabsorción fisiológica ósea posterior a la extracción del diente, conservando la estética. La justificación para la extracción de un diente comprometido a menudo está relacionada con la presencia de una lesión periapical, consecuencia de …

High-Sensitivity Whispering Gallery Mode Humidity Sensor Based on Glycerol Microdroplet Volumetric Expansion

2021

We demonstrate a highly sensitive whispering gallery mode (WGM) relative humidity (RH) sensor based on a glycerol microdroplet. WGMs were excited using a 760 nm tunable semiconductor laser. We used free space coupling, which is effective when using a liquid resonator. A detailed analysis of different parameters influencing the sensor’s characteristics (sensitivity, hysteresis, resolution, stability, and temperature) is presented. The sensitivity of the sensor is one of the highest reported (2.85 nm/% RH in the range 50–70% RH with the resolution 1 × 10−4% RH). This type of humidity sensor has several advantages, such as high sensitivity, extended lifetime, good repeatability, and low cost, …

Síntesis y procesado de materiales inorgánicos por láser

2008

Síntesis y procesado de materiales inorgánicos por láser" tiene como objetivo la utilización de la radiación láser como activador fototérmico de reacciones químicas en estado sólido para producir la síntesis o modificación de materiales inorgánicos. De entre todos los materialesinorgánicos disponibles se han escogido dos grandes conjuntos: cerámica (capítulo II) y vidrio(capítulo III).En el capítulo II se presentan los resultados obtenidos sobre materiales cerámicos en los que la radiación láser actúa como activador de reacciones de síntesis de pigmentos cerámicos (II.2 yII.3), como modificador de la superficie de piezas cerámicas terminadas para fijar pigmentos cerámicos ya sintetizados (I…