The elastic and vibrational properties of a material, bulk or planar waveguide, are studied by BriUouin and Raman spectroscopy to follow the process of nanocrystals growth in glass-ceramics. The nanoparticles cause th...The elastic and vibrational properties of a material, bulk or planar waveguide, are studied by BriUouin and Raman spectroscopy to follow the process of nanocrystals growth in glass-ceramics. The nanoparticles cause the appearance, in the low frequency Raman spectrum, of characteristic peaks, whose position depends on the size of the crystals. At the same time, sharp crystal peaks, due to optical phonons, appear in the Raman spectra, allowing the determination of the nucleated phase, and a frequency shift of the BriUouin peaks is observed.展开更多
We present the details of the sol-gel processing used to realize inverse silica opal,where the silica was activated with 0.3 mol% of Er3+ ions. The template(direct opal) was obtained assembling polystyrene spheres of ...We present the details of the sol-gel processing used to realize inverse silica opal,where the silica was activated with 0.3 mol% of Er3+ ions. The template(direct opal) was obtained assembling polystyrene spheres of the dimensions of 260 nm by means of a vertical deposition technique. The Er3+-activated silica inverse opal was obtained infiltrating,into the void of the template,the silica sol doped with Er3+ ions and subsequently removing the polystyrene spheres by means of calcinations. Scanning electron microscope showed that the inverse opals possess a fcc structure with a air hollows of about 210 nm and a photonic band gap,in the visible range,was observed from reflectance measurements. Spectroscopic properties of Er3+-activated silica inverse opal were investigated by luminescence spectroscopy,where,upon excitation at 514.5 nm,an emission of 4I13/2 → 4I15/2 of Er3+ ions transition with a 21 nm bandwidth was observed. Moreover the 4I13/2 level decay curve presents a single-exponential profile,with a measured lifetime of 18 ms,corresponding a high quantum efficiency of the system.展开更多
Er^3- / Yb^3＋ co - doped silica - alumina monolithic xerogels were prepared with the same concentration on 2 000 Er/Si ppm and 6 000 AI/Si ppm. The Yb/Si content was varied from 0 to 4 000 ppm. Densification of the s...Er^3- / Yb^3＋ co - doped silica - alumina monolithic xerogels were prepared with the same concentration on 2 000 Er/Si ppm and 6 000 AI/Si ppm. The Yb/Si content was varied from 0 to 4 000 ppm. Densification of the samples was achieved by thermal treatment in air at 950 ~C for 120 hours with a heating rate 0.1 ~C / min. Photoluminescence spectroscopy was used to obtain information about the effective excitation efficiency of Er^3＋ ions by co-doping with Yb^3- ions. The infrared-to-visible up-conversion luminescence has been investigated upon continuous wave excitation at 980 nm. The samples exhibit red, green and blue upconversion emission. It is found that the intensity of up-conversion luminescence increases with increasing Yb3- doping concentration. An opposite behavior is observed for the 4 I13/2 luminescence of the Er^3＋ ions.展开更多
基金The present work has been funded partly with the financial supportof MIUR-FIRB RBNE012N3X, MIUR PRIN, PAT FAPVU 2004-2006.
文摘The elastic and vibrational properties of a material, bulk or planar waveguide, are studied by BriUouin and Raman spectroscopy to follow the process of nanocrystals growth in glass-ceramics. The nanoparticles cause the appearance, in the low frequency Raman spectrum, of characteristic peaks, whose position depends on the size of the crystals. At the same time, sharp crystal peaks, due to optical phonons, appear in the Raman spectra, allowing the determination of the nucleated phase, and a frequency shift of the BriUouin peaks is observed.
基金The work has been supported by the MIUR-FIRB RBNE012N3X,MIUR PRIN, PAT FAPVU 2004-2006,GRICES-CNR.
文摘We present the details of the sol-gel processing used to realize inverse silica opal,where the silica was activated with 0.3 mol% of Er3+ ions. The template(direct opal) was obtained assembling polystyrene spheres of the dimensions of 260 nm by means of a vertical deposition technique. The Er3+-activated silica inverse opal was obtained infiltrating,into the void of the template,the silica sol doped with Er3+ ions and subsequently removing the polystyrene spheres by means of calcinations. Scanning electron microscope showed that the inverse opals possess a fcc structure with a air hollows of about 210 nm and a photonic band gap,in the visible range,was observed from reflectance measurements. Spectroscopic properties of Er3+-activated silica inverse opal were investigated by luminescence spectroscopy,where,upon excitation at 514.5 nm,an emission of 4I13/2 → 4I15/2 of Er3+ ions transition with a 21 nm bandwidth was observed. Moreover the 4I13/2 level decay curve presents a single-exponential profile,with a measured lifetime of 18 ms,corresponding a high quantum efficiency of the system.
基金This research is performed in the context of the Italy-Vietnamre-search project 6 BS 2 MAE2006-2008 .MIUR-FIRB RBNE012N3X,PAT FAPVU2004-2006 ,MIUR-PRIN2004-2006 .
文摘Er^3- / Yb^3＋ co - doped silica - alumina monolithic xerogels were prepared with the same concentration on 2 000 Er/Si ppm and 6 000 AI/Si ppm. The Yb/Si content was varied from 0 to 4 000 ppm. Densification of the samples was achieved by thermal treatment in air at 950 ~C for 120 hours with a heating rate 0.1 ~C / min. Photoluminescence spectroscopy was used to obtain information about the effective excitation efficiency of Er^3＋ ions by co-doping with Yb^3- ions. The infrared-to-visible up-conversion luminescence has been investigated upon continuous wave excitation at 980 nm. The samples exhibit red, green and blue upconversion emission. It is found that the intensity of up-conversion luminescence increases with increasing Yb3- doping concentration. An opposite behavior is observed for the 4 I13/2 luminescence of the Er^3＋ ions.
