Search results for " abl"
showing 10 items of 296 documents
Laser heating and ablation at high repetition rate in thermal confinement regime
2006
International audience; Laser heating and ablation of materials with low absorption and thermal conductivity (paint and cement) were under experimental and theoretical investigations. The experiments were made with a high repetition rate Q-switched Nd:YAG laser (10 kHz, 90 ns pulse duration and l = 532 nm). High repetition rate laser heating resulted in pulse per pulse heat accumulation. A theoretical model of laser heating was developed and demonstrated a good agreement between the experimental temperatures measured with the infrared pyrometer and the calculated ones. With the fixed wavelength and laser pulse duration, the ablation threshold fluence of paint was found to depend on the repe…
Luminescence mechanisms of defective ZnO nanoparticles.
2016
ZnO nanoparticles (NPs) synthesized by pulsed laser ablation (PLAL) of a zinc plate in deionized water were investigated by time-resolved photoluminescence (PL) and complementary techniques (TEM, AFM, μRaman). HRTEM images show that PLAL produces crystalline ZnO NPs in wurtzite structure with a slightly distorted lattice parameter a. Consistently, optical spectra show the typical absorption edge of wurtzite ZnO (Eg = 3.38 eV) and the related excitonic PL peaked at 3.32 eV with a subnanosecond lifetime. ZnO NPs display a further PL peaking at 2.2 eV related to defects, which shows a power law decay kinetics. Thermal annealing in O2 and in a He atmosphere produces a reduction of the A1(LO) Ra…
Synthesis of multi-color luminescent ZnO nanoparticles by ultra-short pulsed laser ablation
2020
Abstract Crystalline ZnO nanoparticles (NPs) are synthesized by ultra-short femtosecond (fs) pulsed laser ablation (PLA) of a zinc plate in deionized water, and are investigated by optical absorption and time resolved luminescence spectra in combination with the morphology and structure analysis. The comparison with previous experiments based on short nanosecond (ns) PLA highlights that pulse duration is a crucial parameter to determine the size and the optical properties of ZnO NPs. While short PLA generates NPs with average size S ‾ of ~ 30 nm, ultrashort PLA allows to achieve much smaller NPs, S ‾ ⩽ 10 nm, that evidence weak quantum confinement effects on both the absorption edge and th…
Graphene in strong laser field: experiment and theory
2015
The interaction of graphene nanoparticles and strong 64 fs pulses is examined. We demonstrate high-order harmonic generation in the plasma contained in crumpled sheets of graphene. The morphological studies of the debris of ablated graphene, application of single-color and two-color pumps of graphene-containing plasma, and theoretical consideration of the high-order harmonic generation in this medium are presented.
Study of silica-based intrinsically emitting nanoparticles produced by an excimer laser
2019
International audience; We report an experimental study demonstrating the feasibility to produce both pure and Ge-doped silica nanoparticles (size ranging from tens up to hundreds of nanometers) using nanosecond pulsed KrF laser ablation of bulk glass. In particular, pure silica nanoparticles were produced using a laser pulse energy of 400 mJ on pure silica, whereas Ge-doped nanoparticles were obtained using 33 and 165 mJ per pulse on germanosilicate glass. The difference in the required energy is attributed to the Ge doping, which modifies the optical properties of the silica by facilitating energy absorption processes such as multiphoton absorption or by introducing absorbing point defect…
Laser-Fabricated Fluorescent, Ligand-Free Silicon Nanoparticles: Scale-up, Biosafety, and 3D Live Imaging of Zebrafish under Development
2022
This work rationalizes the scalable synthesis of ultrasmall, ligand-free silicon nanomaterials via liquid-phase pulsed laser ablation process using picosecond pulses at ultraviolet wavelengths. Results showed that the irradiation time drives hydrodynamic NP size. Isolated, monodisperse Si-NPs are obtained at high yield (72%) using post-treatment process. The obtained Si-NPs have an average size of 10 nm (not aggregated) and display photoemission in the green spectral range. We directly characterized the ligand-free Si-NPs in a vertebrate animal (zebrafish) and assessed their toxicity during the development. In vivo assay revealed that Si-NPs are found inside in all the early life stages of …
Luminescent silicon nanocrystals produced by near-infrared nanosecond pulsed laser ablation in water
2014
Abstract We report the investigation of luminescent nanoparticles produced by ns pulsed Nd:YAG laser ablation of silicon in water. Combined characterization by AFM and IR techniques proves that these nanoparticles have a mean size of ∼3 nm and a core–shell structure consisting of a Si-nanocrystal surrounded by an oxide layer. Time resolved luminescence spectra evidence visible and UV emissions; a band around 1.9 eV originates from Si-nanocrystals, while two bands centered at 2.7 eV and 4.4 eV are associated with oxygen deficient centers in the SiO 2 shell.
Effects of the process conditions on the plume of a laser-irradiated indium–tin-oxide target
2001
Abstract The plume of a laser-ablated indium–tin-oxide target was investigated by optical emission spectroscopy. Atomic and ionic species of indium, tin and oxygen were observed; moreover, molecular bands of indium oxide were identified in the fluorescent spectra. The effects of the oxygen as a background gas and of the laser fluence on the behaviour of the ejected particles were studied with respect to the intensity of the emission and the delay time as a function of the observation distance from the target surface. The non-linear behaviour of the fluorescent species with the process conditions could infer spatial variations of the plume composition. The analysis demonstrates a plume expan…
Periodic unmixing of a binary metallic vapor
2005
We report on a type of surface structuring after short pulse laser ablation of a binary alloy. We observe the emergence of a concentric ring structure with changing elemental composition. The composition changes are interpreted by condensation of the ambient ablation vapor due to stress wave excitations in the ablation spot.
Combined hepatectomy and radiofrequency ablation for multifocal hepatocellular carcinoma: a case report
2009
Introduction: At the present time, the best possible choice for the local management of a multifocal hepatocellular carcinoma (HCC) developing on liver cirrhosis is multimodal treatment of the disease. Combined approach based on simultaneous radiofrequency ablation (RFA) together with limited surgical resection represents a valid choice of treatment. Case presentation: A 75-year-old white female patient affected of HCV-associated cirrhosis in BChild-Pugh’s functional class A5, developed a bifocal HCC. The patient had undergone a limited surgical resection together with simultaneous RFA, without intraoperative and postoperative surgical complications. At 36 months after surgery, still shows …