ABSTRACT For the first time, selective sintering of amorphous PtCuNiP powder with a pulsed Nd:YAG... more ABSTRACT For the first time, selective sintering of amorphous PtCuNiP powder with a pulsed Nd:YAG laser has been studied. Upon pulsed interaction, the grains melt only superficially to build necks between the grains. Depending on the laser parameters, the sintered material can be crystallized or retained amorphous. By contrast with crystalline powder, laser sintering of amorphous powder is achieved at substantially lower pulse energies due to its low melting point. The obtained results are compared with previous results from selective laser sintering of titanium powder.
Proceedings of SPIE - The International Society for Optical Engineering, 2001
12 The controlled laser microstructuring of solid surfaces improves their wear properties: microh... more 12 The controlled laser microstructuring of solid surfaces improves their wear properties: microholes induced on a friction surface can act like lubricant reservoirs and as traps for debris particles. In generating such microstructures, the laser has the advantage of its great versatility, since it can be used in various environments and it can be adapted to a wide range of
Proceedings of SPIE - The International Society for Optical Engineering, 2002
The controlled laser patterning of solid surfaces improves their wear properties: laser generated... more The controlled laser patterning of solid surfaces improves their wear properties: laser generated microcraters of defined dimensions and morphology can act as lubricant reservoirs and as traps for wear particles. For generating such microstructures different ...
Proceedings of SPIE - The International Society for Optical Engineering, 2002
ABSTRACT The densification processes occurring in metallic powders upon interaction with pulsed l... more ABSTRACT The densification processes occurring in metallic powders upon interaction with pulsed laser radiation have been studied experimentally and compared with results obtained from a numerical simulation model. The analysis of the sintered samples shows consolidation features, which are in very good agreement with the model predictions. The limited amount of molten material due to pulsed interaction and the recoil pressure exerted on the powder by the plasma and the ablation plume allow to achieve a predetermined density (or porosity) from less than 60% to more than 90% of the bulk density, depending on the laser parameters and processing steps. A wider range of porosity could be achieved by mixture of the metallic powder with later removable spacers of the desired size.
Proceedings of SPIE - The International Society for Optical Engineering, 2003
Investigations on the occurrence of structure and hardness changes (for two sorts of steel and fo... more Investigations on the occurrence of structure and hardness changes (for two sorts of steel and for a hard metal substrate) in the immediate vicinity of laser induced craters are presented in this work. Experiments with femtosecond pulses were performed in air with a Ti:sapphire laser (800 nm, 100 fs) at mean fluences of 2, 5 and 10 J/cm2. Series of
Proceedings of SPIE - The International Society for Optical Engineering, 2003
ABSTRACT The influence of aluminum co-doping and CO2-laser processing on the fluorescence lifetim... more ABSTRACT The influence of aluminum co-doping and CO2-laser processing on the fluorescence lifetime of neodymium doped sol-gel derived silica glasses has been studied. The combination of host material modification and thermal treatment offers a possibility to overcome the limitations set on the fluorescence lifetime of Nd3+-doped silica by clustering, concentration quenching, and phonon quenching. Our study focuses on the fluorescing behavior of the produced samples depending on different methods of thermal annealing and host material modification. We show that neodymium doped sol-gel derived silica glasses, modified with aluminum and treated with a CO2-laser exhibit a fluorescence lifetime of several hudnred microseconds at high dopant concentrations (e.g. 280+/-6mus for a Nd3+-concentration of 1.1×1021 cm-3).
Proceedings of SPIE - The International Society for Optical Engineering, 2006
In recent years, photonic crystal fibres (PCF) have attracted much interest because of their uniq... more In recent years, photonic crystal fibres (PCF) have attracted much interest because of their unique possibilities in mode selection. They allow high index as well as low index core geometries and light guidance is provided either by modified total internal reflection or by the photonic bandgap. An example for the high index guiding type of PCF is the fibre with
2010 23rd Annual Meeting of the IEEE Photonics Society, PHOTINICS 2010, 2010
A bend-insensitive C-band erbium-doped fiber is proposed with strong confinement of the LP01 mode... more A bend-insensitive C-band erbium-doped fiber is proposed with strong confinement of the LP01 mode by six air holes around the core. Bending performances for both pump and signal photons were optimized by parametric analysis.
Proceedings of SPIE - The International Society for Optical Engineering, 2011
The potential of pulsed laser system in the range of 10ps to 100ps pulse duration for material pr... more The potential of pulsed laser system in the range of 10ps to 100ps pulse duration for material processing has been further investigated. In detail the dependency of the volume ablation rate, penetration depth and threshold fluence on the pulse duration and number of pulses applied to the material will be discussed. The experimental results show that in the case of
Proceedings of SPIE - The International Society for Optical Engineering, 2012
ABSTRACT We present our progress in the production of ytterbium (Yb) doped optical fibers fabrica... more ABSTRACT We present our progress in the production of ytterbium (Yb) doped optical fibers fabricated by two variants of the granulated aluminophosphosilicate method. We show advantages and disadvantages of mixing rare earth and aluminophosphosilicate granulated oxides directly (variant 1) or by using the sol-gel method to produce doped granulate material (variant 2). For both methods we studied the effects of varying the dopant concentrations and of introducing iterative melting and milling procedures. In particular, the sol-gel based method eases the inclusion of P2O5 and thus, in combination with Al2O3, higher dopant concentration of Yb and Er are possible. Sintering the sol-gel material at high temperature eliminated bubbles in the core. We fabricated optical fibers that, piecewise, between individual strong scatterers, exhibited attenuation losses as low as 0.35dB/m. For our comparative study we determined volume percentage and distribution of chemical elements in the fabricated fiber glasses by the analytical technique of Energy-Dispersive X-ray, Electro Probe Microanalysis and the degree of crystallization by X-Ray Diffraction analysis. Furthermore we measured fluctuations of the refractive index profile and scattering losses of the fiber core.
ABSTRACT For the first time, selective sintering of amorphous PtCuNiP powder with a pulsed Nd:YAG... more ABSTRACT For the first time, selective sintering of amorphous PtCuNiP powder with a pulsed Nd:YAG laser has been studied. Upon pulsed interaction, the grains melt only superficially to build necks between the grains. Depending on the laser parameters, the sintered material can be crystallized or retained amorphous. By contrast with crystalline powder, laser sintering of amorphous powder is achieved at substantially lower pulse energies due to its low melting point. The obtained results are compared with previous results from selective laser sintering of titanium powder.
Proceedings of SPIE - The International Society for Optical Engineering, 2001
12 The controlled laser microstructuring of solid surfaces improves their wear properties: microh... more 12 The controlled laser microstructuring of solid surfaces improves their wear properties: microholes induced on a friction surface can act like lubricant reservoirs and as traps for debris particles. In generating such microstructures, the laser has the advantage of its great versatility, since it can be used in various environments and it can be adapted to a wide range of
Proceedings of SPIE - The International Society for Optical Engineering, 2002
The controlled laser patterning of solid surfaces improves their wear properties: laser generated... more The controlled laser patterning of solid surfaces improves their wear properties: laser generated microcraters of defined dimensions and morphology can act as lubricant reservoirs and as traps for wear particles. For generating such microstructures different ...
Proceedings of SPIE - The International Society for Optical Engineering, 2002
ABSTRACT The densification processes occurring in metallic powders upon interaction with pulsed l... more ABSTRACT The densification processes occurring in metallic powders upon interaction with pulsed laser radiation have been studied experimentally and compared with results obtained from a numerical simulation model. The analysis of the sintered samples shows consolidation features, which are in very good agreement with the model predictions. The limited amount of molten material due to pulsed interaction and the recoil pressure exerted on the powder by the plasma and the ablation plume allow to achieve a predetermined density (or porosity) from less than 60% to more than 90% of the bulk density, depending on the laser parameters and processing steps. A wider range of porosity could be achieved by mixture of the metallic powder with later removable spacers of the desired size.
Proceedings of SPIE - The International Society for Optical Engineering, 2003
Investigations on the occurrence of structure and hardness changes (for two sorts of steel and fo... more Investigations on the occurrence of structure and hardness changes (for two sorts of steel and for a hard metal substrate) in the immediate vicinity of laser induced craters are presented in this work. Experiments with femtosecond pulses were performed in air with a Ti:sapphire laser (800 nm, 100 fs) at mean fluences of 2, 5 and 10 J/cm2. Series of
Proceedings of SPIE - The International Society for Optical Engineering, 2003
ABSTRACT The influence of aluminum co-doping and CO2-laser processing on the fluorescence lifetim... more ABSTRACT The influence of aluminum co-doping and CO2-laser processing on the fluorescence lifetime of neodymium doped sol-gel derived silica glasses has been studied. The combination of host material modification and thermal treatment offers a possibility to overcome the limitations set on the fluorescence lifetime of Nd3+-doped silica by clustering, concentration quenching, and phonon quenching. Our study focuses on the fluorescing behavior of the produced samples depending on different methods of thermal annealing and host material modification. We show that neodymium doped sol-gel derived silica glasses, modified with aluminum and treated with a CO2-laser exhibit a fluorescence lifetime of several hudnred microseconds at high dopant concentrations (e.g. 280+/-6mus for a Nd3+-concentration of 1.1×1021 cm-3).
Proceedings of SPIE - The International Society for Optical Engineering, 2006
In recent years, photonic crystal fibres (PCF) have attracted much interest because of their uniq... more In recent years, photonic crystal fibres (PCF) have attracted much interest because of their unique possibilities in mode selection. They allow high index as well as low index core geometries and light guidance is provided either by modified total internal reflection or by the photonic bandgap. An example for the high index guiding type of PCF is the fibre with
2010 23rd Annual Meeting of the IEEE Photonics Society, PHOTINICS 2010, 2010
A bend-insensitive C-band erbium-doped fiber is proposed with strong confinement of the LP01 mode... more A bend-insensitive C-band erbium-doped fiber is proposed with strong confinement of the LP01 mode by six air holes around the core. Bending performances for both pump and signal photons were optimized by parametric analysis.
Proceedings of SPIE - The International Society for Optical Engineering, 2011
The potential of pulsed laser system in the range of 10ps to 100ps pulse duration for material pr... more The potential of pulsed laser system in the range of 10ps to 100ps pulse duration for material processing has been further investigated. In detail the dependency of the volume ablation rate, penetration depth and threshold fluence on the pulse duration and number of pulses applied to the material will be discussed. The experimental results show that in the case of
Proceedings of SPIE - The International Society for Optical Engineering, 2012
ABSTRACT We present our progress in the production of ytterbium (Yb) doped optical fibers fabrica... more ABSTRACT We present our progress in the production of ytterbium (Yb) doped optical fibers fabricated by two variants of the granulated aluminophosphosilicate method. We show advantages and disadvantages of mixing rare earth and aluminophosphosilicate granulated oxides directly (variant 1) or by using the sol-gel method to produce doped granulate material (variant 2). For both methods we studied the effects of varying the dopant concentrations and of introducing iterative melting and milling procedures. In particular, the sol-gel based method eases the inclusion of P2O5 and thus, in combination with Al2O3, higher dopant concentration of Yb and Er are possible. Sintering the sol-gel material at high temperature eliminated bubbles in the core. We fabricated optical fibers that, piecewise, between individual strong scatterers, exhibited attenuation losses as low as 0.35dB/m. For our comparative study we determined volume percentage and distribution of chemical elements in the fabricated fiber glasses by the analytical technique of Energy-Dispersive X-ray, Electro Probe Microanalysis and the degree of crystallization by X-Ray Diffraction analysis. Furthermore we measured fluctuations of the refractive index profile and scattering losses of the fiber core.
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Papers by Valerio Romano