We report the fluorescent properties of 3D localized structure with size near the diffraction limit induced by femtosecond direct laser writing (DLW) in Yb3+ and silver-containing phosphate glass. The homogenous dispersion of the silver ions and Yb3+ ions in the glass matrix before DLW was evidenced using photo-luminescent spectroscopy and time-resolved spectroscopy. Using high repetition rate femtosecond DLW, the inscription of 3D visible and near-infrared fluorescent patterns formed by co-localization of silver cluster and Yb3+ ions was demonstrated. The local refractive index change associated with the formation of silver clusters is dependent on the laser irradiance. Confocal micro-luminescent spectroscopy for excitation wavelength in the visible range shows efficient emission of Yb3+ only on DLW induced 3D fluorescent patterns. This finding demonstrated the ability to perform thanks to DLW laser a resonant efficient nonradiative energy transfer from silver clusters to Yb3+ and allows 3D writing of near-infrared luminescence.

Three-dimensional (3D) femtosecond laser direct structuring in transparent materials is widely used for photonic applications. However, the structure size is limited by the optical diffraction. Here we report on a direct laser writing technique that produces subwavelength nanostructures independently of the experimental limiting factors. We demonstrate 3D nanostructures of arbitrary patterns with feature sizes down to 80 nm, less than one tenth of the laser processing wavelength. Its ease of implementation for novel nanostructuring, with its accompanying high precision will open new opportunities for the fabrication of nanostructures for plasmonic and photonic devices and for applications in metamaterials. ©2009 Optical Society of America OCIS codes: (160.5335) Photosensitive materials; (190.4720) Optical nonlinearities of condensed matter; (320.2250) Femtosecond phenomena; (350.3450) Laser-induced chemistry. References and links 1. R. R. Gattass, and E. 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17 The effect of P2O5 and/or Al2O3 addition in Er-doped borosilicate glasses on the physical, 18 thermal, optical and luminescence properties is investigated. The changes in these glass properties 19 are related to the glass structure modifications induced by the addition of P2O5 and/or Al2O3, which 20 were probed by FTIR, 11 B MAS NMR and X-ray photoelectron spectroscopies. Variations of the 21 polymerization degree of the silicate tetrahedra and modifications in the [3] B/ [4] B ratio are explained 22 by a charge compensation mechanism due to the formation of AlO4, PO4 groups and the formation 23 of AlOP linkages in the glass network. From the absorption and luminescence properties of the 24

The effect of P2O5 and/or Al2O3 addition in Er-doped borosilicate glasses on the physical, thermal, optical, and luminescence properties is investigated. The changes in these glass properties are related to the glass structure modifications induced by the addition of P2O5 and/or Al2O3, which were probed by FTIR, B-11 MAS NMR and X-ray photoelectron spectroscopies. Variations of the polymerization degree of the silicate tetrahedra and modifications in the B-[3]/B-[4] ratio are explained by a charge compensation mechanism due to the formation of AlO4, PO4 groups and the formation of Al-O-P linkages in the glass network. From the absorption and luminescence properties of the Er3+ ions at 980 nm and 1530 nm, declustering is suspected for the highest P2O5 concentrations while for the highest Al2O3 concentrations no declustering is observed. (C) 2014 Elsevier Ltd. All rights reserved.

In this paper, the absorption properties of Er3+-doped borosilicate glasses with various P2O5 and Al2O3 content are measured for different silica concentrations. The Judd-Ofelt parameters (Omega(2), Omega(4) and Omega(6)) have been calculated in order to investigate the local environment of the rare-earth cations. The compositional changes of Omega(2) and Omega(6) are attributed to changes in the bonding between Er3+ and surrounding ligand groups due to structural modifications occurring with the introduction of P2O5 and Al2O3. The luminescence quantum efficiency of the I-4(13/2) -> I-4(15/2) transition slightly increases with the addition of P2O5 whereas it decreases with the progressive replacement of P2O5 by Al2O3. We noticed that it also increases when the silica content is higher. (C) 2014 Elsevier B.V. All rights reserved.

We report results on the processing and characterization of different glass preforms and single core fibers within the SiO2-Na2O-B2O3-Er2O3-P2O5-Al2O3 system. Micro-Raman spectroscopy was used to identify post-draw structural modification. The differences in the micro-Raman spectra recorded on the preform and on the fiber glass were attributed to a change in the structure induced by the drawing process. Changes in the silicate network organization and small scale molecular orientation within the glass matrix are suspected to occur during the fiber drawing process. We found that the extent in the changes between the preform and fiber properties depend on the glass composition. The glass network of the Al-containing fiber is expected to be less sensitive to the drawing process than that of the fiber matrix as the network of this Al-containing fiber is formed by a larger number of Si-BO units in the network and neutral three-coordinated boron compared to the network of the fiber matrix. From the micro-Raman spectra, formation of small crystals is suspected to occur in the P-containing glasses during the fiber drawing process. The resulting fibers were found to have propagation losses at 1330 nm and Er3+ absorption between (7 +/- 1) and (25 +/- 1) dB/m and (36 +/- 1) and (47 +/- 1) dB/m, respectively, depending on the glass composition. (C) 2014 Elsevier B.V. All rights reserved.

Thermal stress at 100 degrees C for more than 3168 h of a fluorescent optical memory composed of laser written silver nano clusters embedded in glass has been performed. Measurements of luminescence spectra have been carried out at different times, showing a decreasing and an increasing evolution of the red and the blue part of the spectrum, respectively. This evolution has been attributed to the diffusion and the reorganization of different silver species inside the matrix, altering the internal electric field. Stark effect based modeling enables the degradation mode of the memory. (C) 2013 Elsevier Ltd. All rights reserved.

Various photo-induced silver luminescent centres were obtained in photosensitive zinc and phosphate glasses containing silver ions after exposure to gamma or ultraviolet nanosecond pulsed-laser radiation. Gamma-irradiation of the glasses results mainly in the formation within the glass of electron-trapped and hole-trapped silver centres as evidenced by optical absorption, luminescence and electron spin resonance spectroscopies. For the highest irradiation doses silver clusters are obtained. Under ultraviolet nanosecond pulsed-laser exposure similar species are generated along the beam propagation direction as proven by the analogous optical and luminescence signatures. In this case for high irradiation doses few silver clusters are created. The evolution of the luminescence spectra with respect to the temperature and to the duration of the heat treatment after ultraviolet nanosecond pulsed-laser irradiation evidences the presence of potential barriers determining the stability limits of some species such as the Ag2+ hole-trapped centres or the Agmx+ clusters composed of silver ions and silver atoms. A heat treatment of several hundreds of degrees is identified as a the key parameter for tailoring the optical properties and controlling the formation of Agmx+ clusters in the photosensitive glasses.

Luminescent structures have been implemented by direct laser writing using high repetition rate femtosecond laser in a silver ion containing photosensitive glass. The optical and luminescence properties have been investigated and compared to those measured after irradiation by a nanosecond laser followed by a thermal treatment. Analogous signals were obtained, demonstrating that the femtosecond direct laser writing combines in one single operation both a photomodification of the silver oxidation states, and a strong local concentration of silver clusters thanks to the high repetition rate. The comparative study confirms the remarkable stability of the photo-induced species with respect to the temperature.

Silver ions activated phosphate based glasses allow fabricating multi-scale designed materials, after electric field or laser structuring. The control of the silver ions distribution or the local redox chemistry are important for optical property tailoring.

We report on spatially and spectrally-resolved linear optical properties induced by Direct Laser Writing in a prepared silver-doped phosphate glass, opening interesting possibilities for elementary photonics bricks. The formation mechanism of optical structures is proposed.

We demonstrate that direct femtosecond laser writing in silver-containing zinc and gallium phosphate glass enables generation of three-dimensional (3D) optical second-order nonlinear microstructures having an χ(2) value about 2.5 times that of quartz. The proposed physical model involves photo-reduction, photo-dissociation, and migration of silver species within the glass matrix. 3D laser-written second-order nonlinear structures could become a new class of nonlinear optical components.

This paper presents an overview of the research in glasses for photonics currently performed at the Department of Applied Science and Technology , Politecnico di Torino, with an emphasis on active silica glasses and novel tellurite glasses for photonics

The chemical durability of glasses with the composition 40P2O5–55ZnO–1Ga2O3–4Ag2O and 41P2O5–51ZnO–8Ga2O3 (mol%) was studied by measuring the rates of aqueous dissolution in neutral, acidic and alkaline aqueous solutions and discussed as a function of the glass composition. The change in the pH of the solutions as a function of the immersion time of the samples was used to study the dissolution mechanism. Using XRD and SEM/EDXA, we showed that the dissolution in deionized (DI) water and HCl consists of the leaching of the phosphate chains into the medium along with (i) the formation of a hydrated layer with the composition Zn2P2O7·3H2O and also of AgCl agglomerates when immersed in HCl and (ii) a leaching out of P, Ga and Ag when immersed for more than 180min in DI water and for more than 60min in HCl. The dissolution in NaOH–Na2CO3 consists of a net consumption of the OH− along with the formation of layers of Zn3(PO4)2·(H2O)4 and Zn(H2PO2)2·H2O with no apparent diffusion of P, Ga and Ag when immersed for as long as 240min. Increasing the Ga2O3 concentration in zinc-phosphate glass at the expense of Ag2O lowers the dissolution rate when immersed in DI water, HCl and NaOH–Na2CO3 probably due to a reinforcement of the glass network.

La focalisation de lasers a impulsions ultra-breves dans les verres a montre des potentialites importantes pour la structuration des materiaux transparents, permettant d'envisager la realisation de dispositifs tout-optique en une seule etape. Le developpement de nouveaux materiaux vitreux de composition 40P2O5-55ZnO-xAg2O-(5-x)Ga2O3 permet de tirer avantage de la photosensibilite de l'ion Ag+ pour la structuration de proprietes optiques au cœur du materiau. L'augmentation du taux d'oxyde de gallium provoque la depolymerisation des chaines phosphates et s'accompagne de la reticulation du reseau vitreux par des polyedres GaOx (4 ≤ x ≤ 6). La formation de des derniers n'affecte pas les proprietes d'emission lumineuses, qui proviennent des ions Ag+ isoles dans differents sites cristallographiques. L'exposition des verres sous faisceau laser intense provoque la formation de centres-trous Ag2+, responsables d'une luminescence intense, et de pieges d'electrons Ag0. Un traitement thermique consecutif ou simultane a l'irradiation provoque la dissociation de ces especes, et s'accompagne de la formation d'agregats moleculaires de la forme Agmx+. L'utilisation d'un laser femtoseconde a haute cadence permet, en combinant creation de paires electron-trou et elevation locale de la temperature, de realiser des architectures complexes conduisant a la structuration de proprietes optiques.

Three-dimensional optical recording by laser-induced fluorescent silver clusters is demonstrated in glass. The fluorescence properties of these stable clusters can be altered, depending on the glass recording exposure conditions. A "Blu-ray"-like drive enables readout of the information inside the glass without cross-talk and photobleaching. This original recording medium can provide an answer to the societal problem of long-term high-density data storage.

To better understand the interactions between organic (natural flavonol) and inorganic (alum) constituents of “Stil de grain”, yellow lake model compounds based on quercetin as a chromophore were prepared and compared in terms of color and stability with those of historical, reconstituted samples. The extraction process of the natural dyes was optimized by varying the quantity of Rhamnus berries, the solvent, the temperature, the time and the extraction method in order to evaluate the role of the natural dye composition on the lake properties. The samples (chromophores and their Al(III) complexes embedded in an aluminum hydroxide matrix) were characterized by high performance liquid chromatography-photodiode array (HPLC-PDA), UV–Visible spectroscopy and X-ray photoelectron spectroscopy (XPS). The conditions of preparation (solvent, temperature, time, extraction method) were correlated to physico-chemical features. Extraction of quercetin from the lake was optimized by using acetic acid buffer and ultrasound. This procedure will enable an improved analysis to be made of current historical materials.