Doped Sodium Borate Glasses Research Articles

Photochromic 3D Optical Storage: Laser‐Induced Regulation of Localized Optical Basicity of Glass

Abstract3D optical storage, spatially expanding storage capacity, is regarded as an effective and economical way to break the diffraction limit of the conventional 2D optical storage. In this study, a new kind of 3D optical storage medium, i.e., vanadium ions (V5+) doped sodium borate glass, is developed, showing intriguing spatially‐selected photochromism (PC) upon laser driven excitation. Significantly, a brand‐new PC mechanism of V5+‐aggregation regulated by localized optical basicity (OB) of glass is proposed and demonstrated. The developed PC glass is responsive to a low‐price desktop‐level mini‐laser to encode optical information, yields unique twofold decoding modes in bright‐ and dark‐fields, and shows good data erasibility. 3D volumetric optical storage with a memory density of ≈480 Mbit cm−3 is realized with the aid of an advanced femtosecond laser micro‐machining system. The findings suggest a novel design approach to fabricate 3D PC glass in terms of manipulating the scale of optical basicity in glass, hopefully stimulating the development of new multi‐dimensional PC optical storage media.

Silver nanoparticles improved infrared photoluminescence of Nd3+ doped sodium borate glasses

Method of melting and quenching was used to prepare the alkali borate–based glasses embedded with Nd3+ ions and silver nanoparticles (Ag NPs). In the as–prepared glass, silver NPs were formed by loading the thermal reducing agent such as antimony trioxide in the composition. The optical absorption and microscopic outcomes confirmed the growth of silver NPs in the prepared glass system. The prepared glass was annealed at 450 °C for 0, 5, 10, 15, and 25 hrs to tune the spectroscopic and photoluminescence features of Nd3+ ions loaded in the glass. The photoluminescence intensity and related features were enhanced continuously with heat treatment schedule. However, subsequently the features were reduced at longer schedule. The variation of these features was ascribed to the local field–generated silver NPs. The results revealed that the entitled glass could be utilized for photonic and optoelectronic applications when activated with Nd3+ ions and routed with Ag NPs.

Effect of Gamma Irradiation on Structural and Optical Properties of Zirconium Incorporated Sodium Borate Glasses

ABSTRACT The effects of gamma irradiation in the dose rate of 25 kGy on the structural and optical properties of ZrO2 doped sodium borate glasses were studied. Glassy nature confirmed by XRD and all the physical parameters were calculated. IR spectra revealed the characteristic vibrational and stretching bands due to trigonal and tetrahedral borate network. Slight changes were caused by gamma irradiation in the intensities of the characteristic infrared borate bands and zirconium bands. Irradiated samples developed a noticeable absorption band similar to the F-band familiar in alkali halide crystals which clearly indicated that successive irradiation produced defects in the glass material. Substitution of ZrO2 to the glass matrix suppressed the formation of visible absorption band formed by irradiation whereas no extra peak was observed in the spectral regions. A nonlinear trend was ascribed in the energy band gap values due to the creation of more number of non-bridging oxygen atoms. Emission spectra showed five emission bands corresponding to the zirconium ions which decreased to a very low intensity with a red shift after irradiation. Matching the colour co-ordinates bright blue emission was found for 5 mol% ZrO2 in both irradiated and non irradiated sample.

Contribution of Eu ions on the precipitation of silver nanoparticles in Ag-Eu co-doped borate glasses

Ag+ doped sodium borate glasses with different Eu ions concentration were prepared by the melt-quenching method. The absorption at about 410nm which was caused by the surface plasmon resonance (SPR) of Ag nanoparticles (NPs) is promoted with increasing of Eu ions concentration. Meanwhile, the luminescent spectra showed that the emission intensity of Ag+ decreased while that of the Ag aggregates increased simultaneously. The results indicated that the Ag ions intend to form the high-polymeric state such as Ag aggregates and nanoparticles with increasing of europium ions. Owing to the self-reduction of Eu3+ to Eu2+ in our glass system, it revealed that Ag+ has been reduced by the neighboring Eu2+ which leads to the formation of Ag aggregates and the precipitation of Ag NPs in the matrix. In addition, energy transfer (ET) process from Ag+/Ag aggregates to the Eu3+ was investigated for the enhancement of Eu3+ luminescence.

Optical Characterization of Erbium Doped Sodium Borate Glass

Borate glass has been identified as one of the potential host for optical application. In this work, a serie of borate glass of the system (80-x) B203 –10Na2O- 10ZnO- x Er2O3 (x= 0.5 -1.5 mol %) has been prepared by melt quenched technique. Their optical properties by mean of the UV-VIS-IR and photoluminescence have been identified. From the result, there are 5 significant absorption peaks that corresponds to 487 nm, 750 nm, 820 nm,894 nm and 979 nm wavelength have been observed. Meanwhile there are six significant emission peaks have been observed which corresponds to 401 nm, 434 nm, 481.5 nm, 526 nm, 556 nm and 700 nm wavelength. Thus, from the photoluminescence results, the green, yellow and red spectrum can be expected. Some other results will be analysed and discussed.

Synthesis and Optical Characterization of Silver Doped Sodium Borate Glasses

Silver doped sodium borate glasses prepared by melt-quenching technique were checked by XRD technique for their amorphous nature. It is observed that the molar volume increases with increasing Ag2O content leading to open struc- ture. Fourier Transform Infrared spectroscopy (FTIR) reveals the formation of BO3 and BO4 groups upon addition of silver oxide as modifier. From the Ultraviolet-Visible (UV-VIS) absorption spectra it is seen that the optical band gap increases with the increase of Ag2O content. Urbach energy is observed between 0.55 - 0.77 eV. The results obtained from molar volume, Fourier Transform Infrared spectroscopy and band gap energy measurements are in agreement with each other and nearly give the similar information about the studied glasses.

Optical properties and ultrafast optical nonlinearity of Yb3+ doped sodium borate and bismuthate glasses

In this paper, we report the optical and ultrafast nonlinear optical properties of Yb3+ doped sodium borate and bismuthate glasses. The glasses have been prepared through the melt quench technique. Optical absorption measurements show compositional dependent absorption spectrum of Yb3+, which is due to the higher crystal field induced by Bi3+ ions. Local structure of the glasses has been identified by using Fourier transform infrared and Raman studies. From open aperture z-scan measurements done by using 100 fs laser pulses, the ultrafast optical nonlinearity in these materials is calculated at the nonresonant excitation wavelength of 800 nm. The measured three-photon absorption originates from the glass host, with contributions from the nonbridging oxygens and the nonlinear electronic polarization of the Bi3+ ions.

Spectral diffusion broadening by soft local modes in Sm 2+-doped sodium borate glass

An explanation for the anomalous temperature broadening of zero-phonon transition corresponding to 7F 0↔ 5D 0 electronic transition in Sm 2+–doped sodium borate glasses is given. The main broadening mechanism is spectral diffusion induced by thermal fluctuation of long-living soft localized modes over the whole studied temperature region 5–293 K.

Temperature and pressure dependence of the homogeneous width of 7F 0– 5D 0 electronic transition in Sm 2+-doped sodium borate glass

The homogeneous width Γ h of 7F 0↔ 5D 0 transition in Sm 2+ ions doped into sodium borate glass was determined at T=5–293 K under P=1 bar and at T=5, 80 and 120 K under various P up to 8 kbar. The line width Γ h was obtained from spectral hole burning (SHB) and time-resolved resonant fluorescence line narrowing (FLN) experiments. It was found that at P=1 bar the T-dependence of Γ h changes from Γ h( T)∝ T 2 (quadratic) for T<20 K to Γ h( T)∝ T (linear) for T>20 K. Under pressure, Γ h grows slightly at all three T values studied (at 80 K by 1.2%/kbar and at 120 K by 1.6%/kbar in the range 0–8 kbar). Possible mechanisms to explain the observed T- and P-dependences of Γ h are briefly discussed.

포토폴리머와 희토류이온이 첨가된 유리에서의 이광자흡수를 이용한 광정보저장

We studied feasibility of three-dimensional optical memory by utilizing femtosecond laser-induced changes of transmission in photopolymers and photoluminescence in Eu and Sm ion doped sodium borate glasses. We produced transmission change by two photon absorption and obtained sub-Um size spots in photopolymers using 780 nm modelocked Ti-sapphire laser pulses. We also changed valence state of Eu and Sm ions by multi-photon absorption and achieved sized spot formation in Sm-doped glasses.

Optical absorption and fluorescence properties of Er3+ in sodium borate glass

Spectroscopic properties of Er3+ ions in sodium borate glass have been studied. The indirect and direct optical band gaps (Eopt) and energy level parameters (RacahE 1, E2 and E3), spin-orbit (ξ4f) and configurational interaction (α)) are evaluated. Spectral intensities for various absorption bands of Er3+ doped sodium borate glass are calculated. Using Judd-Ofelt intensity parametersΩ 2, Ω4, Ω6, radiative transition probabilities (A), branching ratios (β) and integrated absorption cross sections (Σ) are reported for certain transitions. The radiative lifetimes (τR) for different excited states are estimated. From the fluorescence spectra, the emission cross section (σP) for the transition,4I13/2 → 4I15/2 is reported.

Effect of TiO 2 on electron paramagnetic resonance, optical transmission and dc conductivity of vanadyl doped sodium borate glasses

Glass systems with composition xTiO 2·(30− x)Na 2O·70B 2O 3 (series I) and xTiO 2·(70− x)B 2O 3·30Na 2O (series II) containing 2 mol% V 2O 5 have been prepared (0≤ x≤7, mol%) by normal melt-quenching. The electron paramagnetic resonance (EPR) spectra of VO 2+ ions have been recorded in the X-band (∼9.13 GHz) at room temperature. Spin Hamiltonian parameters, g ||, g ⊥, A ||, A ⊥, the dipolar hyperfine coupling parameter ( P) and the Fermi contact interaction parameter ( K) have been calculated. The increase in Δ g ||/Δ g ⊥ with increase in TiO 2 content in series I shows that the octahedral symmetry of V 4+O 6 complex is reduced, whereas in series II the octahedral symmetry is improved with increase in x. The decrease in P, in both the series, indicates that the 3d xy orbit expands with increase in mol% of TiO 2. The molecular orbital coefficients, α 2 and γ 2 have been calculated by recording the optical transmission spectra in the range 500–850 nm. α 2 and γ 2 increase with increase in x in both the series, which indicates that, the covalency of the vanadium oxygen bonds decreases. The dc conductivity σ, decreases and activation energy, W increases with increase in TiO 2:Na 2O ratio whereas with increase in TiO 2:B 2O 3 ratio the variation in σ and W is within experimental error.

Effect of the addition Y2O3 on persistent spectral hole burning in europium doped sodium borate glass

Persistent hole burning is observed in a europium doped sodium borate glass from 10 to 100 K. Hole burning efficiency increased 18× when 5% yttrium oxide was added to the glass mixture. Hole burning was observed up to 300 K in Eu3+, Y3+ Co-doped glass.

Photochemical reactions of samarium ions in sodium borate glasses irradiated with near-infrared femtosecond laser pulses

Photoinduced processes of Sm 3+-doped sodium borate glasses under high-power, 800 nm femtosecond laser irradiation have been studied. Both the photoreduction of Sm 3+ to Sm 2+ and the formation of intrinsic defects are observed at an irradiance well below the threshold for laser-induced damage. We propose that these photoinduced processes arise from the linear and two-photon absorption of the short-wavelength component of the supercontinuum and the subsequent ionization of the glass matrix. Photochemical hole burning (PHB) has been observed for 5 D 0– 7 F 0 transition of Sm 2+ in the sodium borate glasses irradiated with near-infrared femtosecond laser pulses. The efficiency of hole burning at 77 K was about 5 times higher in the irradiated glasses than in thermally reduced glasses. We consider that both the metastable Sm 2+ and the intrinsic defects were responsible for the highly efficient PHB phenomenon.

Ultrashort-laser-pulse-induced persistent spectral hole burning of Eu^3+ in sodium borate glasses

We have observed persistent spectral hole burning (PSHB) in Eu(3+) -doped sodium borate glasses irradiated with near-IR femtosecond laser pulses. As-prepared glasses, i.e., glasses melted in air, do not show PSHB even at low temperatures (~77K) , but room-temperature PSHB occurs in the irradiated glasses. The exposure to IR radiation causes both the reduction of Eu(3+) to Eu(2+) and the formation of intrinsic defects. We propose that the photoinduced redistribution of electric charges between Eu(3+) to Eu(2+) is responsible for the occurrence of PSHB.

Photochemical Hole Burning of Sm2+ in Sodium Borate Glasses Induced by Near-Infrared Femtosecond-Laser Irradiation.

We report on photochemical hole burning of Sm2+ in sodium borate glasses irradiated with femtosecond-laser pulses of 800nm wavelength. The irradiation of Sm3+-doped sodium borate glasses with femtosecond-laser pulses causes electron-trapped Sm3+, i.e., Sm2+ and point defects such as an oxygen hole center and an electron trapped near Na+. The measurements of spectral hole burning were carried out for the 5D0-7F0 transition of Sm2+ using a DCM dye laser. Photoionization hole burning is observed at 77K to room temperature for the glasses exposed to femtosecond-laser pulses, and also for the glasses prepared by melting under reducing conditions. The hole-burning efficiency of Sm2+ produced by the photoinduced process is about twice higher than that by the thermal process. It is thought that the metastable Sm2+ ions and oxygen hole centers induced by femtosecond-laser irradiation are responsible for the observed phenomenon. We propose that the efficient photoionization hole burning is caused by the photostimulated recombination of the electron trapped by Sm3+ with the oxygen hole center.

Electrical properties of CuO doped sodium borate glasses

Electrical conduction in transition metal oxide (TMO) glasses is generally explained on the basis of the small polaron theory. Present results on CuO doped sodium borate glasses seem to be inexplicable on the basis of the above model. Experimental data on dc and ac conductivities of CuO doped sodium borate glasses at different frequencies are presented. It is found that these results can be explained in terms of the concept of small ionic polarons developed for superionic conductors.

Molecular Dynamic Simulation of Eu3+ ‐Doped Sodium Borate Glasses and Their Fluorescence Spectra

A molecular dynamic simulation was performed for sodium borate glasses containing a small amount of Eu2O3 to investigate the local structures of cations in glass. A new potential VB‐B in the form ‐A exp[‐C(r ‐ 0.239)2] was added to the regular modified Born‐Mayer‐Huggins‐type potentials, ΦB‐B, ΦB‐O, and ΦO‐O, to account for the directional tendency of the borate network structure. With this potential added, both the radial distribution of sodium borate glasses observed by small‐angle X‐ray diffraction and the change in coordination number of boron with sodium content obtained by NMR agreed well with the simulation. The average coordination number of Ed3+ ions in the simulated glasses varied from 7.5 to 8.6, depending on the composition of the host sodium borate glasses. The inhomogeneous line width of the 5D0‐7Fz emission peak also changed, depending on the sodium content, with a maximum at 18 mol% NazO content; this result agrees well with experimental data obtained from laser‐induced fluorescence spectra.

“Sensitized” Stress Build-up in Doped Sodium Borate Glasses by Ultraviolet Irradiation

“Sensitized” Stress Build-up in Doped Sodium Borate Glasses by Ultraviolet Irradiation