Iustyna Vasilchenko

Rare-earth doped materials for optical waveguides

In the paper the analysis of luminescence emission in the VIS spectra range of fabricated multicomponent glasses doped with rare-earth ions and PMMA doped with dyes were presented. Up-conversion emission in: germanate glass co-doped with 0.5Yb₂O₃/0.75Eu₂O₃ mol% under 976 nm excitation has been investigated. Down-conversion mechanism was analyzed in phosphate glasses doped with 0.5 mol% Tb₂O₃ and PMMA co-doped with fluorescein and rhodamine B. Phosphosilicate glasses doped with Er³⁺ ions have been also studied in order to fabricate target for manufacturing planar waveguides by RF-sputtering deposition. Fabricated materials can be used for fabrication of optical fibers. In result blue up-conversion emission in double-clad optical fiber with Yb³⁺/Tm³⁺- doped core was presented.

Influence of phosphorous precursors on spectroscopic properties of Er3+-activated SiO2-HfO2-P2O5 planar waveguides

(70-x)SiO2-30HfO2 -xP2O5 (x= 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.

Glass based structures fabricated by rf-sputtering

In this paper we present some results obtained by our consortium regarding rf-sputtered glass-based structures.

RF-sputtering derived phosphosilicate planar waveguides activated by Er 3+ ions

SiO₂-P₂O₅-HfO₂-Al₂O₃-Na₂O planar waveguide was fabricated by rf-sputtering technique. The optical, structural and morphological parameters were measured by various techniques such as m-line spectroscopy, Energy Dispersive X-ray Spectroscopy and Atomic Force Microscopy. The waveguide exhibits a single propagation mode at 1319 and 1542 nm with an attenuation coefficient of 0.2 dB/cm in the infrared. The emission of ⁴I_13/2 → ⁴I_15/2 transition of Er³⁺ ion, with a 28.5 nm bandwidth was observed upon TE0 mode excitation at 514.5 nm. The optical and spectroscopic features of the Er³⁺-activated parent P₂O₅-SiO₂-Al₂O₃-Na₂O glass were also investigated.

Phosphate-based glasses and nanostructures

A group of nanocrystalline polyphosphates is presented showing the advantages arising from their spectroscopic properties. Their unique optical features are related, among others, with their structural properties. For example, reduced cross relaxation processes between doped lanthanide ions are observed in tetraphosphate matrices due to the relatively large active ions distance. For selected praseodymium doped polyphosphates, such as LiPr(PO3)4, a cascade emission transitions can be observed due to the two-step 4f2 transitions that take place under UV excitation into 4f5d levels. Such property could be used for scintillation devices. Other interesting behavior is the efficient anti-Stokes white broadband emission induced by NIR laser diode in LiYb(PO3)4 nanocrystals. Additionally, the properties of planar waveguides based on SiO2-HfO2 system and doped with P2O5 or tetraphosphate nanocrystals are presented.

Glass-based confined structures enabling light control

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, its 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...

Glass-ceramics for photonics: Advances and perspectives

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.

Glass-based confined structures fabricated by sol-gel and radio frequency sputtering

Abstract. Some of the main results obtained in the field of glass-based photonic crystal (PC) systems using complementary techniques, such as radio frequency (RF) sputtering and sol-gel route, are presented. Initially, rare earth-activated one-dimensional PCs fabricated by RF-sputtering technique will be discussed, specifically the cavity is constituted by an Er3+-doped SiO2 active layer inserted between two Bragg reflectors consisting of 10 pairs of SiO2/TiO2 layers. Moreover, from near infrared, transmittance and variable angle reflectance spectra have verified the presence of a stop band from 1500 to 2000 nm with a cavity resonance centered at 1749 nm at 0 deg and quality factor of 890. In the second case, a composite system based on polystyrene colloidal nanoparticles assembled and embedded in an elastomeric matrix will be presented in detail. This system has been designed as a structure that displays an iridescent green color that can be attributed to the PC effect. This feature has been exploited to create a chemical sensor; in fact optical measurements have evidenced that this system presents a different optical response as a function of the solvent applied on the surface, showing: (1) high sensitivity, (2) fast response, and (3) reversibility of the signal change.

Glass-Based Photonic Crystals: From Fabrication to Applications

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 solvents that can be also easily observed by the naked eye. Optical measurements have evidenced a red shift of the diffraction peak as a function of the solvents applied. This feature has been exploited in order to create a sensitive material showing high sensitivity and reversibility of the signal change.

Glass-Based Sub-Wavelength Photonic Structures

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.