Papers by Alessandro Chiasera
Optical Materials, 2018
In this work, we focused on the syntheses, structure and spectroscopic properties of GdVO4:Dy 3þ ... more In this work, we focused on the syntheses, structure and spectroscopic properties of GdVO4:Dy 3þ and DyVO4 (nano)particles of different sizes and shapes (spherical nanoparticles of 2 nm, 4 nm, and 20 nm in size, nanorods with a few nanometers in diameter and up to 10e20 nm in length and microparticles of 1 e8 mm) obtained by four synthetic methods. The size effect on the structure, Raman active modes, and photoluminescence emission intensities was analyzed by X-ray diffraction, Raman and photo-luminescence spectroscopy, scanning and transmission electron microscopy, and diffuse reflection spectroscopy. All Xray diffraction patterns clearly indicated presence of a single tetragonal zircon-type phase; absence of impurity phases indicate that the dopant Dy 3þ ions were successfully and uniformly incorporated into the GdVO4 host lattice due to the equal valence and similar ionic radii. Micro-Raman measurements support the XRD measurements and showed Raman-active modes of the REVO4 systems (RE ¼ Gd, Dy). The difference between the two hosts in the diffuse reflectance spectra was observed and it could be attributed to more effective Gd 3þ ions on the charge transfer bands and different polarization (compared to bulk material) in smaller nanoparticles. Photoluminescence spectroscopy showed several bands in the visible and near-infrared regions which can be exclusively attributed to the fef transitions of Dy 3þ ions. .
Journal of Non-Crystalline Solids, 2003
Two Er 3þ /Yb 3þ-codoped 92SiO 2-8TiO 2 planar waveguides, with 1.2 mol% Er and molar ratio Er/Yb... more Two Er 3þ /Yb 3þ-codoped 92SiO 2-8TiO 2 planar waveguides, with 1.2 mol% Er and molar ratio Er/Yb of 2, were fabricated by rf-sputtering technique. The active films were deposited on silica-on-silicon and silica glass substrates. The thickness of the waveguides and the refractive index at 632.8 and 543.5 nm were measured by an m-line apparatus. The losses, for the TE 0 mode, were evaluated at 632.8 and 1300 nm. The structural properties were investigated by energy dispersive spectroscopy and Raman spectroscopy. All waveguides were single-mode at 1550 nm. An attenuation coefficient of 0.5 dB/cm at 632.8 nm and 0.1 dB/cm at 1300 nm were measured. The emission at 1530 nm of the 4 I 13=2 ! 4 I 15=2 transition of Er 3þ ion was observed at room temperature upon continuous wave excitation at 981 and 514.5 nm. Back energy transfer from Er 3þ to Yb 3þ was demonstrated by measurement of Yb 3þ emission upon Er 3þ excitation at 514.5 nm. Effective excitation efficiency of Er 3þ ions by co-doping with Yb 3þ ions was shown by photoluminescence excitation spectroscopy.
Materials
The unique properties of the Eu3+ ion make it a powerful spectroscopic tool to investigate struct... more The unique properties of the Eu3+ ion make it a powerful spectroscopic tool to investigate structure or follow processes and mechanisms in several high-tech application areas such as biology and health, structural engineering, environment monitoring systems and quantum technology, mainly concerning photonics. The traditional method is to exploit the unique photoluminescent properties of Eu3+ ions to understand complex dynamical processes and obtain information useful to develop materials with specific characteristics. The objective of this review is to focus on the use of Eu3+ optical spectroscopy in some condensed matter issues. After a short presentation of the more significant properties of the Eu3+ ion, some examples regarding its use as a probe of the local structure in sol–gel systems are presented. Another section is devoted to dynamical processes such as the important technological role of nanocrystals as rare-earth sensitizers. The appealing effect of the site-selection mem...
2015 17th International Conference on Transparent Optical Networks (ICTON), 2015
Transparent glass-ceramics, activated by luminescent species, present an important class of photo... more Transparent glass-ceramics, activated by luminescent species, present an important class of photonic materials because their specific optical, spectroscopic and structural properties. Several top-down and bottom-up techniques have been developed for transparent glass ceramic fabrication. Among them laser material processing plays an important role and many significant results have been obtained in the field of waveguide glass ceramics fabrication. Here, after a short description of the state of art regarding laser material processing for glass ceramics, we report on the specific use of CO2 laser for the fabrication of transparent glass ceramic waveguides.
EPJ Web of Conferences
Flexible SiO2/HfO2 1D photonic crystals and active SiO2–HfO2:Er3+ all-glass flexible planar waveg... more Flexible SiO2/HfO2 1D photonic crystals and active SiO2–HfO2:Er3+ all-glass flexible planar waveguides fabricated by radio frequency sputtering, are presented. The 1D photonic crystals show a strong dependence of the optical features on the light incident angle: i) blue-shift of the stopband and ii) narrowing of the reflectance window. Nevertheless, the most interesting result is the experimental evidence that, even after the 1D photonic crystals breakage, where the flexible glass shows naked-eye visible cracks, the multilayer structures generally maintain their integrity, resulting to be promising systems for flexible photonic applications thanks to their optical, thermal and mechanical stability. The flexible planar waveguides, fabricated on ultrathin flexible glass substrate, showed an attenuation coefficient lower than 0.2 dB/cm at 1.54 μm, and exibits emission in the NIR region, resulting particularly suitable as waveguide amplifier in the C band of telecommunications.
Applied Sciences, 2021
This work presents an analysis of the crystallization process and the influence of laser surface ... more This work presents an analysis of the crystallization process and the influence of laser surface modification on the crystalline phases and optical responses of Al2O3/glass–ceramic coatings deposited on a brass substrate. We used a CO2 laser at different irradiation powers to change the structure of the superficial layer. The photoluminescence response enhanced the resolution of its line shape as the irradiation power increased. X-ray diffraction patterns exhibit the presence of different crystalline phases for the samples irradiated.
Proceedings of SPIE - The International Society for Optical Engineering, 2002
Er3+/Yb3+-codoped 92SiO2-8TiO2 planar waveguides, with 1.2 mol% Er and molar ratio Er/Yb of 2, we... more Er3+/Yb3+-codoped 92SiO2-8TiO2 planar waveguides, with 1.2 mol% Er and molar ratio Er/Yb of 2, were fabricated by rf-sputtering technique. The active films were deposited on silica-on-silicon and v-SiO2 substrates. The parameters of preparation were chosen in order to optimize the waveguides for operation in the NIR region with particular attention to the minimization of the losses. The thickness of the waveguides and the refractive index at 632.8 and 543.5 nm were measured by an m-line apparatus. The losses, for the TE0 mode, were evaluated at 632.8 and 1300 nm. The structural properties were investigated with several techniques such as Secondary Ion Mass Spectrometry, Energy Dispersive Spectroscopy and Raman Spectroscopy. All waveguides were single-mode at 1550 nm. An attenuation coefficient of 0.5 dB/cm at 632.8 nm and 0.1 dB/cm at 1300 nm were measured. The emission of 4I13/2 --> 4I15/2 of Er3+ ion transition with a 40 nm bandwidth was observed upon excitation at 981 and 514.5 nm in the TE0 mode. Back energy transfer from Er3+ to Yb3+ was demonstrated. Photoluminescence excitation spectroscopy was used to obtain information about the effective excitation efficiency of Er3+ ions by co-doping with Yb3+ ions.
Proceedings of SPIE - The International Society for Optical Engineering, 2003
SiO-TiO: Er-Yb waveguides were prepared by rf-sputtering technique. The active films were deposit... more SiO-TiO: Er-Yb waveguides were prepared by rf-sputtering technique. The active films were deposited on silica-on-silicon and v-SiO substrates. The parameters of preparation were chosen in order to optimize the waveguides for operation in the NIR region with particular ...
Proceedings of SPIE - The International Society for Optical Engineering, 2005
Titre Optical and spectroscopic properties of erbium-activated modified silica glass with 1.54 μm... more Titre Optical and spectroscopic properties of erbium-activated modified silica glass with 1.54 μm high quantum efficiency Type de publication Communication Type Communication avec actes dans un congrès Année 2005 Langue Anglais Date du colloque 24-25/01/2005 Titre du colloque Integrated Optoelectronic Devices 2005 Optical Components and Materials II Volume 5723
2015 17th International Conference on Transparent Optical Networks (ICTON), 2015
ABSTRACT
International Conference on Fibre Optics and Photonics, 2012
ABSTRACT Large enhancement in nonlinear absorption (NLA) was observed in 1-D photonic crystal con... more ABSTRACT Large enhancement in nonlinear absorption (NLA) was observed in 1-D photonic crystal containing ZnO defect fabricated by rf sputtering. The enhancement in NLA is due to the strong confinement of the optical field around the defect layer.
We report experimental results on the characterization of microspherical cavities fabricated in E... more We report experimental results on the characterization of microspherical cavities fabricated in Er3+-doped modified-silica and phos- phate glasses. The spectroscopic properties of the bulk precursor glasses as compared to the obtained microspheres were investigated by photoluminescence spectroscopy and lifetime measurement for the 4I13/2 ! 4 I15/2 transition of Er 3+ ions. In both types of glasses we dem- onstrate whispering gallery mode laser action at various wavelengths around 1550 nm by using a 1480 nm pump laser coupled through a tapered fiber.
Journal of Physics: Conference Series, 2014
ABSTRACT (70-x)SiO2-30HfO2 -хP2O5 (х= 5, 10 mol %) glass planar waveguides activated by 0.5 mol% ... more ABSTRACT (70-x)SiO2-30HfO2 -хP2O5 (х= 5, 10 mol %) glass planar waveguides activated by 0.5 mol% Er3+ ions were prepared by sol–gel route. Several phosphorous precursors have been investigated for the synthesis of a dielectric stable sol useful for the realization of planar waveguides. The waveguides were investigated by different diagnostic techniques. The optical properties such as refractive index, thickness, number of propagating modes and attenuation coefficient were measured at 632.8 and 543.5 nm by prism coupling technique.Transmission measurements were carried out in order to assess the transparency of the deposited films. Photoluminescence measurements and lifetime decay curves of the Er3+ transition (4I13/2 →4I15/2) were performed in order to investigate the role of P2O5.
When a luminescent ion is confined in a system characterized by one or more specific properties s... more When a luminescent ion is confined in a system characterized by one or more specific properties such as spatial size, geometrical dimension and shape, refractive index, local crystal field, cut-off vibrational energy and so on, it's possible to control its emission. The control of branching ratios as a function of the composition, the luminescence enhancement induced by a photonic crystal, or the laser action in a microresonator, are well known examples of light control. Photonic glass-based structures are extremely viable systems to exploit the above mentioned properties and in our research team we have successfully fabricated luminescent photonic structures by different techniques, including sol-gel, rf sputtering, drawing, melting, and physical vapour deposition. Here we will discuss some of them with the aim to make the reader aware of the chemical-physical properties related to each specific system. We will demonstrate that glass ceramic waveguides in some cases present superior spectroscopic propert...
Optical and Quantum Electronics, 2014
The sol-gel technique is a very flexible, relatively simple, and low-cost method to fabricate man... more The sol-gel technique is a very flexible, relatively simple, and low-cost method to fabricate many different innovative photonic structures characterized by specific functionalities. During synthesis, starting from the molecular level, compounds or composites with well controlled composition can be obtained as thin films, powders or monoliths. These materials can be used to prepare such structures as waveguides, photonic crystals, coatings, and bulk glasses including spheres, rings and other geometries exploited in optical resonators fabri
Advances in Science and Technology, 2014
We report on the fabrication and on the assessment of the properties of two glass-based photonic ... more We report on the fabrication and on the assessment of the properties of two glass-based photonic crystals (PhCs) obtained using alternative approaches such as rf-sputtering and sol-gel techniques. (i) By means of rf-sputtering a one-dimensional dielectric photonic crystal constituted by an Er3+-doped SiO2 active layer inserted between two Bragg reflectors consisting of 10 pairs of SiO2∕TiO2 layers has been realized. Near infrared transmittance spectra evidenced the presence of a stop band from 1500 to 2000 nm with a cavity resonance centered at 1749 nm. Intensity enhancement and narrowing of the emission band of Er3+ ions, due to the cavity effect have been observed and a cavity quality factor of 890 has been achieved. (ii) Through chemical route a 3D colloidal crystal based on polystyrene (PS) nanoparticles (NPs) embedded in elastomeric matrix has been realized. In the specific has been shown that the structure can produce a variation of its color applying different organic solvent...
2014 16th International Conference on Transparent Optical Networks (ICTON), 2014
Glass-ceramics are nanocomposite materials which offer specific characteristics of capital import... more Glass-ceramics are nanocomposite materials which offer specific characteristics of capital importance in photonics. This kind of two-phase materials is constituted by nanocrystals embedded in a glass matrix and the respective composition and volume fractions of crystalline and amorphous phase determine the properties of the glass-ceramic. Among these properties transparency is crucial, in particular when confined structures, such as dielectric optical waveguides, are considered, and several works have been devoted to this topic. Another important point is the role of the nanocrystals when activated by luminescent species, as rare earth ions, and their effect on the spectroscopic properties of the glass-ceramic. The presence of the crystalline environment around the rare earth ion allows high absorption and emission cross sections, reduction of the non-radiative relaxation thanks to the lower phonon cut-off energy, and tailoring of the ion-ion interaction by the control of the rare earth ion partition. Fabrication, assessment and application of glass-ceramic photonic systems, especially waveguides, deserve an appropriate discussion which is the aim of this paper, focused on luminescent glass-ceramics. In this work, a brief historical review, consolidated results and recent advances in this important scientific and technological area will be presented, and some perspectives will be outlined.
2013 15th International Conference on Transparent Optical Networks (ICTON), 2013
ABSTRACT Fabrication of confined structures, where light can be confined over nano or micro scale... more ABSTRACT Fabrication of confined structures, where light can be confined over nano or micro scale region is fantastic challenge for nano-science based technologies. Manufacture of such structures has become possible due to the opportunity delivered by nanotechnology, which opens the way to the study of new functional artificial materials and plasmonic structures, promising progress in miniaturization and which allow exploration of new aspects of light-matter interaction. The exploitation of their unique properties covers a range of applications possibilities and system performance that are not solely ICT oriented but also concern Lighting; Laser, Sensing, Energy, Environment, and Health. Here we will discuss about glass-derived novel nano and micrometer scale range structures such as microcavities, waveguides, microresonators, transparent glass-ceramics, and photonic crystals mainly fabricated by sol-gel and rf-sputtering techniques, evidencing the capital scientific and technological interest of this kind of structures, which require and allow common multidisciplinary research involving scientists coming from a large spectrum of disciplines. Attention will be focused on the structural and spectroscopic properties of such systems that, when activated by rare earth ions, represents the cornerstone in a wide number of technological applications such as integrated optical amplifiers, laser systems, and solar energy converters.
physica status solidi (c), 2014
Optical Materials, 2009
This paper reports about recent advances in optical nanomaterials and planar microcavities. Botto... more This paper reports about recent advances in optical nanomaterials and planar microcavities. Bottom-up fabrication, optical and spectroscopic assessment of Er 3+-activated SiO 2-HfO 2 waveguide glass ceramic are presented. Concerning confined structures, the rf sputtering based fabrication of an Er 3+-activated microcavity with a quality factor of 171 using oxide-based dielectric materials is demonstrated.
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Papers by Alessandro Chiasera