Ion-exchanged Glass Research Articles

Hybrid erbium-doped DFB waveguide laser made by wafer bonding of two ion-exchanged glasses

Er-doped and Er/Yb-codoped glasses have a key role in the production of lasers and amplifiers for optical communication systems and eye-safe sensors operating at wavelengths around 1550nm. Ion-exchanged waveguides on Er/Yb-codoped phosphate glass allow implementing quite compact and efficient active devices. Unfortunately, these wafers are not compatible with the integration of passive functions since unpumped erbium ions absorb 1550nm signal. Hence, an efficient monolithic co-integration of passive and active optical functions requires hybridizing doped and undoped glasses. In this paper, we present the realization of a fully encapsulated three-dimensional distributed feedback (DFB) hybrid laser obtained by the wafer bonding of two ion-exchanged substrates. On the first one, an undoped silicate glass, a selectively buried channel core waveguide is made by a Ag+/Na+ exchange and a field-assisted burial. A Bragg grating is then etched on the wafer surface. On the second wafer, an Er/Yb-codoped phosphate glass, a slab core waveguide is obtained by a Ag+/Na+ exchange. The two wafers are finally bonded together yielding to a DFB laser: the interaction between the guided light and the doped glass provides the amplification, while the Bragg grating supplies the feedback. With this fully encapsulated device, (420±15)µW laser emission has been observed at 1534nm for (390±20)mW injected pump power, while its input and output are totally insulated from the doped wafer.

Formation of silver fractal structures in ion-exchange glasses under poling

In silver-ion-containing ion-exchange glasses subjected to a constant electric field and temperature, fractal silver structures arise under the surface facing the cathode. The growth of the structures is characterized by random branching and the absence of self-crossings: the main part of the fractal is in the glass, and some ends of the branches emerge on the surface. As a possible application of substrates with fractal structures thus prepared, the determination of their surface-enhanced Raman scattering activity using Rhodamine 6G dye is described.

이온강화 소다라임 유리의 열처리에 따른 강화 풀림현상

Recently, the use of ion-exchange strengthened glass has increased sharply, as it is now used as the cover glass for smart phone devices. Therefore, many researchers are focusing on methods that can be used to strengthen ion-exchange glass. However, research on how the improved strength can be maintained under thermal environment of device manufacturing is still insufficient. We tested the degradation of the characteristics of ion-exchange soda-lime glass samples, including their surface compressive stress characteristics, the depth of the ion-exchange layer (DOL), flexural strength, hardness, and modulus of rupture (MOR) values. Degradation of the characteristics of the ion-exchange glass samples occurred when they were heat-treated at a temperature that exceeded 350℃.

Physics and chemistry of antimicrobial behavior of ion-exchanged silver in glass.

The results of a comprehensive study involving the antimicrobial activity in a silver ion-exchanged glass are presented. The study includes the glass composition, the method of incorporating silver into the glass, the effective concentration of the silver available at the glass surface, and the effect of the ambient environment. A quantitative kinetic model that includes the above factors in predicting the antimicrobial activity is proposed. Finally, experimental data demonstrating antibacterial activity against Staphylococcus aureus with correlation to the predicted model is shown.

Study of selectively buried ion-exchange glass waveguides using backside masking

In this Letter, we study the characteristics of a selectively buried glass waveguide that is fabricated by the backside masking method. The results show that the surface region appears when the width of the backside mask is larger than 7 mm. Here, the glass substrate is 1.5 mm thick. It is also found that the buried depth evolution of the transition region remains almost unchanged and is independent of the width of the backside mask. The loss of the transition region is only 0.28 dB at the wavelength of 1.55 μm if the surface condition is good enough.

GISAXS study on the size and distribution evolutions of Ag nanoparticles in ion-exchange glass during annealing

Silver-doped silicate composite glass had been synthesized with an ion-exchanged method. Grazing incidence small angle X-ray scattering (GISAXS) technique was used to investigate the size and distribution evolutions of Ag nanoparticles in the glass matrix in a subsequent thermal treatment process. GISAXS experiment reveals a change of size distribution of Ag nanoparticles from bimodal distribution to one-size distribution in annealing at 300 °C. The results demonstrate that the normalized volume fraction of smaller particles with average diameter of 6.4 nm almost no changed, but the bigger metastable ones dissolved gradually in an exponential decay way during the annealing process. It can be concluded that a multilayer nanostructure composed of silver nanoparticles was formed in the thermal process.

Nd^3+-doped ion-exchanged aluminum germanate glass channel waveguide

K+–Na+ ion-exchanged channel waveguide has been fabricated in Nd3+ doped aluminum germanate (NMAG) glasses with potential photosensitive property. The channel waveguide exhibits single mode at 1.3μm and the mode field diameters were measured to be horizontally 10.1μm and vertically 5.3μm, respectively. Amplified spontaneous emissions (ASE) of 905, 1060, 1334 and 1816nm originating from the 4F3/2 level were recorded under ~800nm diode laser pumping and the maximum stimulated emission cross-sections for the 4F3/2→4I11/2 and 4F3/2→4I13/2 transitions are derived to be 21.5 × 10−21 and 7.6 × 10−21cm2, respectively. In addition, with 71.8% quantum efficiency and the largest emission intensity among various Nd3+ doping cases, 2wt% Nd2O3 is considered as the optimized doping concentration for the compact channel waveguide. The ion-exchanged Nd3+-doped NMAG glass channel waveguides offer favorable prospects for the development of optical waveguide amplifiers, broadband light sources and infrared UV-written grating waveguide lasers.

Influence of Cu+ cations on photoluminescence properties of Tb3 + in Cu+–Na+ ion-exchanged sodium-borosilicate glasses

Cu+ cations were introduced into the sodium-borosilicate (SBS) glasses via a Cu+–Na+ ion-exchanged technique. The photoluminescence (PL) properties of Cu+, Tb3+ single- and co-activated SBS glasses, and the energy transfer (ET) process from Cu+ to Tb3+ cations were systematically investigated through energy-level diagram, decay curves, absorption spectra, PL excitation and emission spectra. Under the excitation of UV-light, Cu+-activated SBS glasses emit blue-greenish photons in the visible range, originating from the 3d94s1→3d10 transition of Cu+ cations. Moreover, the intensities of the excitation and emission bands of Cu+ can be tailored by appropriately tuning the ion-exchange time. Significantly, enhancement of green emission of Tb3+ was observed via utilization of Cu+ cations as efficient sensitizers. The influence of the ion-exchange temperature and the salt bath with varied ratios of CuSO4 to Na2SO4 on the interaction between Cu+ and Tb3+ cations was also discussed. Our research will help understand the enhancement mechanisms of Tb3+ emissions in Cu+/Tb3+-codoped amorphous systems.

Plasmonic molecules via glass annealing in hydrogen.

Growth of self-assembled metal nanoislands on the surface of silver ion-exchanged glasses via their thermal processing in hydrogen followed by out-diffusion of neutral silver is studied. The combination of thermal poling of the ion-exchanged glass with structured electrode and silver out-diffusion was used for simple formation of separated groups of several metal nanoislands presenting plasmonic molecules. The kinetics of nanoisland formation and temporal evolution of their size distribution on the surface of poled and unpoled glass are modeled.PACS78.67.Sc (nanoaggregates; nanocomposites); 81.16.Dn (self-assembly); 68.35.bj (surface structure of glasses); 64.60.Qb (Nucleation); 81.16.Nd (micro- and nanolithography)

SERS-applicable silver nanoisland film grown under protective coating

We have used recently developed out-diffusion technique of growing silver nanoisland films on glass surface to grow silver nanoislands under TiO2 layer deposited on the glass. After covering the surface of silver ion-exchanged glasses with TiO2 film using atomic layer deposition technique and subsequent thermal processing of the samples in hydrogen their optical absorption spectra demonstrate the absorption peak corresponding to surface plasmon resonance in grown silver nanoislands. The spectral position of the peak is shifted relatively to the peak observed in the spectra of the nanoisland film grown on the surface of ion exchanged and annealed glass samples without dielectric cover. The applicability of the silver nanoislands grown under several nm thick protective TiO2 coating in surface-enhanced Raman scattering spectroscopy is demonstrated.

Fabrication of lightweight and thin bulletproof windows using borosilicate glass strengthened by ion exchange

Borosilicate glass was strengthened by ion-exchange for lightweight bulletproof windows. The conditions for ion-exchange for strengthening borosilicate glass (3, 4 and 6mm thick) produced the ultimate mechanical properties at 560°C for each duration of 10, 12 and 15min. The flexural strength values of the ion-exchanged glass with thickness of 3, 4 and 6mm were 0.745, 0.783 and 0.810 GPa, respectively, which were about 2.8 times higher than parent glass. A lightweight bulletproof window could thus be manufactured from strengthened glass with a ballistic velocity of 889.4m/s. The transmittance of bulletproof windows (over 86%) satisfied the international standards.

Out-diffused silver island films for surface-enhanced Raman scattering protected with TiO2 films using atomic layer deposition.

We fabricated self-assembled silver nanoisland films using a recently developed technique based on out-diffusion of silver from an ion-exchanged glass substrate in reducing atmosphere. We demonstrate that the position of the surface plasmon resonance of the films depends on the conditions of the film growth. The resonance can be gradually shifted up to 100 nm towards longer wavelengths by using atomic layer deposition of titania, from 3 to 100 nm in thickness, upon the film. Examination of the nanoisland films in surface-enhanced Raman spectrometry showed that, in spite of a drop of the surface-enhanced Raman spectroscopy (SERS) signal after the titania spacer deposition, the Raman signal can be observed with spacers up to 7 nm in thickness. Denser nanoisland films show slower decay of the SERS signal with the increase in spacer thickness.PACS78.67.Sc (nanoaggregates; nanocomposites); 81.16.Dn (self-assembly); 74.25.nd (Raman and optical spectroscopy)

Molecular dynamics simulations of ion-exchanged glass

Chemically strengthened glass is one of the key enablers of the modern consumer electronics industry. Molecular dynamics simulations offer an opportunity to build enhanced fundamental understanding of the ion exchange process used for chemical strengthening. In this work, we apply molecular modeling techniques to investigate several aspects of ion-exchanged glasses that are either inaccessible through experiment or too difficult to probe through experiments alone. In particular, we use atomistic modeling to study the dependence of the linear network dilation coefficient on the concentration of alkali ions exchanged. We also calculate the evolution of elastic moduli as a result of the ion exchange process. Both of these quantities—the network dilation coefficient and the Young's modulus—are critical parameters for determining the final compressive stress profile of the chemically strengthened glass. Finally, we revisit the issue of structural differences between as-melted and ion-exchanged glasses in terms of local atomic number density around alkali ions. The results of this work point to the unique structures attainable through ion exchange that cannot be achieved through melt-quenching alone.

Generation of silver nanoparticles with controlled size and spatial distribution by pulsed laser irradiation of silver ion-doped glass

Silver ions were driven into glass by a direct current electric field-assisted ion exchange technique. The silver ion exchanged glass was then irradiated by laser pulses of 10 ns and 10 ps in length at 355 nm for comparison purposes. In both cases, laser irradiation led to the formation of a metallic-like film at the surface of the ion exchange glass. Scanning electron microscopy showed that the films consist of a very dense single layer of silver nanoparticles with similar particle sizes and separation. Irradiation with different laser parameters shows no significant difference in transmission spectra and modification width between ps- and ns-pulsed lasers. Particle sizes and separation at the surface are increasing with increasing laser power, and are larger for picosecond pulsed laser irradiation. It is also shown that the film formation is a thermal process.

Effect of gamma rays absorbed doses and heat treatment on the optical absorption spectra of silver ion-exchanged silicate glass

Samples of a commercial silicate glass have been subjected to ion exchange at 320°C in a molten mixture of AgNO3 and NaNO3 with molar ratio of 1:99 and 5:95 for 60min. The ion exchange process was followed by gamma irradiation in the dose range of 1–250kGy and heating at the temperature of 550°C for different time periods ranging from 10 to 582min. The spectral absorption in UV–Vis range of the Ag–Na ion exchanged glass was measured and used to determine the states of silver prevailing in the glass during the ion exchange, the gamma irradiation and the heat treatment. The gamma irradiation induced holes and electrons in the glass structure leading to the creation of a brown colour, and silver ions trapped electrons to form silver atoms. We observed the first stage of aggregation after irradiation, as well as after heating. The silver atoms diffused and then aggregated to form nanoclusters after heating at 550°C. A characteristic band at about 430nm was induced. The surface Plasmon absorption of silver nanoclusters in the glass indicated that the nanoclusters radius grew between 0.9 and 1.43nm with increasing of annealing time from 10 to 242min and then saturated. We also found that the size of aggregates depends on the value of gamma radiation absorbed dose. Contrary to what was expected, we found that 20kGy is the optimal absorbed dose corresponding to the larger size of the aggregates which decreases for absorbed doses above 20kGy.

A direct approach for modeling ion-exchange residual stress distribution in glass

In this article, we propose a direct approach to model the residual stress in glass due to ion exchange. Rather than employing the traditional thermal strain analogy approach in literature, the nominal residual strain distribution due to ion exchange is addressed with direct analysis of ion-exchange volume change first. Then, based on the principle of superposition, the residual stress in ion-exchanged glass is then formulated with a direct approach in the framework of elasticity, and a complete solution for residual stress distribution is obtained with consideration of the asymmetric ion molar concentration distribution. Finally, a simple example is provided to demonstrate the validity of the fundamental formulations proposed in this article.

Non-conservation of the total alkali concentration in ion-exchanged glass

Chemically strengthened glasses are widely used in applications requiring high scratch and damage resistance, such as cover glass for personal electronic devices. Chemical strengthening occurs by replacing the smaller alkali ions in the glass by larger alkali ions from a molten salt bath, whereby a surface layer with high compressive stress is installed. The mechanical properties of chemically strengthened glass strongly depend on the magnitude of the compressive stress, which in turn is proportional to the concentration of exchanged alkali ions. It has hitherto been assumed that the total amount of alkali ions in the glass is conserved during the ion exchange (e.g., in the Nernst–Planck model). In this work, we immerse alkali aluminosilicate glasses [30M2O·10Al2O3·60SiO2 (mol%)] in MNO3 salt baths containing identical alkali ions (where M=Li, Na, K). We demonstrate a non-conservation of the total amount of alkali ions in the glass during the ion exchange process. Generally we find that the smaller ions exhibit a net flux into the glass, while the larger ions demonstrate a net flux into the salt bath. Moreover, the total amount of alkali ions in the top surface layer is not conserved in sodium and potassium aluminosilicate glasses after ion exchange. We explain these findings based on the thermodynamic driving force difference in alkali oxides residing in glass or nitrate salt. The results are important for chemical strengthening applications, since the direction of flux and the non-conservation of alkali ions affect the final compressive stress of an ion exchanged glass.

Vibrational study of thermally ion-exchanged sodium aluminoborosilicate glasses

Thermally ion-exchanged M+-for-Na+ (M=K and Ag) aluminoborosilicate glasses were obtained from the glass (SiO2)60(B2O3)10(Al2O3)6(Na2O)20.2(ZrO2)3.7(Sb2O3)0.1 (in mol%) and studied by infrared reflectance and micro-Raman spectroscopy. The results of both techniques are consistent with local structural rearrangements induced by ion-exchange below glass transition temperature, Tg, and are expressed for the silicate network by the chemical equilibrium Q2+Q4⇔2Q3 where Qn represents a silicate tetrahedron with n bridging oxygen atoms. Replacement of Na+ by K+ was found to shift this equilibrium to the right, while the introduction of Ag+ ions causes the opposite effect. Micro-Raman depth profiling showed that these structural changes occur within a layer whose thickness depends on the type of the guest cation and the conditions of ion-exchange; the thickness is about 50μm for Ag+ ions exchanged at 340°C for 180min and about 40μm for K+ exchanged at 325°C for 6h.

Enhanced fluorescence and optical power limiting in Ag-nanocomposite glasses

In this letter, we prepared and studied the plasmon, fluorescence and optical limiting properties of silver ion-exchanged glasses followed by an external thermal treatment for clusterization inside the glass matrix. TEM (Transmission electron microscopy) studies of the prepared samples provides information about the size of the nanoclusters, their size enhancement after TA (Thermal annealing) and supports the SPR band shape variations from the UV–Vis. absorption studies. Enhancement in fluorescence and optical-limiting (with excitation near to resonant value of the SPR) is ascribed to the amplified local field after metal nanocluster growth by thermal annealing.

Formation and 2D-patterning of silver nanoisland film using thermal poling and out-diffusion from glass

We fabricated silver nanoisland films and patterned silver nanoisland films using out-diffusion of silver from glass in the course of the ion-exchanged glass substrate annealing in reducing hydrogen atmosphere. The choice of the annealing conditions allows to provide prevailing of silver nanoisland formation over the formation of silver nanoparticles in the bulk of the glass. The procedure of the patterned film formation includes (i) silver-sodium ion exchange in the glass, (ii) thermal poling of the ion-exchanged glass with a profiled anodic electrode, and (iii) annealing the glass in hydrogen. The formation of silver nanoislands in unpoled regions on the glass surface allowed us to avoid any post-processing of very fragile silver island film in formation of 2D-patterned nanoisland structures. Poling of the glass with properly profiled electrode was used for the formation of random chains and ordered arrays of separate silver nanoislands. Depending on processing parameters, a typical island size in the films and chains varied from several to tens of nanometers, and was down to 200 nm in the arrays.