Silica Glass Fiber Research Articles

Gold Enhanced Hemoglobin Interaction in a Fabry–Pérot Based Optical Fiber Sensor for Measurement of Blood Refractive Index

A Fabry–Perot based optical fiber sensor to measure the oxygen concentration through monitoring the change of refractive index in red blood cells is reported. The optical fiber sensor with a diameter of 220 μm is made entirely of fused silica glass fibers, which can be integrated within standard brachytherapy seed delivery needle to be used in vivo . Isopropanol solution and pig blood are prepared to produce refractive index in the range 1.344–1.365. Gold is coated to a thickness of 100 nm at the tip of the sensor to enhance the interaction between hemoglobin and light. A fast Fourier transform algorithm is used to analyze the phase angle from the reflected output spectrum. The gold-coated sensor has up to almost ten times higher sensitivity to hemoglobin concentration in blood solutions compared to isopropanol solutions. A sensitivity of 9.82 rad/RIU with a refractive index resolution of 2.09 × 10–3 RIU is achieved for the sensor with a 16 μm thickness diaphragm.

Ultra-fast polymer optical fibre Bragg grating inscription for medical devices

We report the extraordinary result of rapid fibre Bragg grating inscription in doped polymer optical fibres based on polymethyl methacrylate in only 7 ms, which is two orders of magnitude faster than the inscription times previously reported. This was achieved using a new dopant material, diphenyl disulphide, which was found to enable a fast, positive refractive index change using a low ultraviolet dose. These changes were investigated and found to arise from photodissociation of the diphenyl disulphide molecule and subsequent molecular reorganization. We demonstrate that gratings inscribed in these fibres can exhibit at least a 15 times higher sensitivity than silica glass fibre, despite their quick inscription times. As a demonstration of the sensitivity, we selected a highly stringent situation, namely, the monitoring of a human heartbeat and respiratory functions. These findings could permit the inscription of fibre Bragg gratings during the fibre drawing process for mass production, allowing cost-effective, single-use, in vivo sensors among other potential uses.

A study of the thermal protective performance of the outer fabric material for fire proximity suits

The thermal performances such as thermal conductivity, radiant heat reflection, X-ray diffraction spectra, thermogravimetric data, and thermal protection performance (TPP) of three types of outer fabric materials for fire protection suits were compared. Three types of fire proximity suits’ outermost fabrics are high silica glass fiber fabrics (A1), high silica glass fiber fabrics (B1), and continuous basalt fiber fabrics (XW). The explanation and analysis of the reasons for the difference in thermal protective performance among the three types of materials were carried out, one by one, from the perspective of the microscopic molecular architecture of the yarn and macroscopic fabric structure. The sizes of the influence for related indicators of all types of thermal performances on the TPP value of the fabric were calculated. According to the analysis and calculation results, it can be concluded that the thermal conductivity of the fabric is the decisive factor influencing the size of the TPP value for the fabric. Therefore, reducing the thermal conductivity of the fabrics and improving the thermal insulation efficiency of the fabric is the best way to improve their thermal protective performance.

Synthesis of silica glass fibers and nanoparticles by continuous-wave laser backside irradiation

We have developed a novel method to synthesize fibers and nanoparticles of silica glass using a continuous-wave laser. The synthesis process operates through continuous-wave laser backside irradiation (CW-LBI) of a glass substrate. In CW-LBI, a spindle-shaped emission is generated in the glass bulk along the optical axis; the emission propagates toward the light source as a confined plasma. The emission and its surroundings contain vaporized and molten glass. When the laser irradiation continues for a sufficient duration, the emission forefront reaches the glass surface, at which point vaporized and molten glass are ejected explosively. The ejected glass forms fibers and nanoparticles. Some of the nanoparticles become attached to the fiber surfaces during the explosion. The fiber diameters range from hundreds of nanometers to more than 10 μm. The particles on the fiber surfaces have diameters of tens of nanometers. A spindle-shaped hole remained in the glass substrate after the ejection, which had a depth of ~3.8 mm. This result indicated that the ejected materials originated from deep inside the glass bulk. High-speed camera observations of the ejection process and scanning electron microscopy of the ejected materials indicated that the fibers formed from the extraction from molten silica glass and particles formed by aggregation of vaporized silica glass.

Preparation of fumed silica compacts for thermal insulation using wet processing method

AbstractThis paper describes the preparation of fumed silica compacts for thermal insulation, using wet processing method. A series of thermal insulation compacts based on fumed silica powder and glass fibers were prepared. The influence of the mass ratio about fumed silica and glass fibers on the fracture strength and thermal conductivity was investigated. The results showed that the fracture strength increased first and then decreased with the mass ratio increasing. The thermal conductivity decreased linearly with the mass ratio increasing. When the compact was pressed under 6 MPa with a mass ratio of 5:1, it exhibited excellent thermal insulation at room temperature with a thermal conductivity of 0.042W/mK. Moreover, the compact was hydrophobic, after being modified by KH‐570.

Multi-step cure kinetic model of ultra-thin glass fiber epoxy prepreg exhibiting both autocatalytic and diffusion-controlled regimes under isothermal and dynamic-heating conditions

As packaging technologies are demanded that reduce the assembly area of substrate, thin composite laminate substrates require the utmost high performance in such material properties as the coefficient of thermal expansion (CTE), and stiffness. Accordingly, thermosetting resin systems, which consist of multiple fillers, monomers and/or catalysts in thermoset-based glass fiber prepregs, are extremely complicated and closely associated with rheological properties, which depend on the temperature cycles for cure. For the process control of these complex systems, it is usually required to obtain a reliable kinetic model that could be used for the complex thermal cycles, which usually includes both the isothermal and dynamic-heating segments. In this study, an ultra-thin prepreg with highly loaded silica beads and glass fibers in the epoxy/amine resin system was investigated as a model system by isothermal/dynamic heating experiments. The maximum degree of cure was obtained as a function of temperature. The curing kinetics of the model prepreg system exhibited a multi-step reaction and a limited conversion as a function of isothermal curing temperatures, which are often observed in epoxy cure system because of the rate-determining diffusion of polymer chain growth. The modified kinetic equation accurately described the isothermal behavior and the beginning of the dynamic-heating behavior by integrating the obtained maximum degree of cure into the kinetic model development.

A Novel Approach for Preparation and In Situ Tensile Testing of Silica Glass Membranes in the Transmission Electron Microscope

The mechanical behavior of glasses in the micro- and/or nanometer regime increasingly gains importance in nowadays modern technology. However, suitable small scale preparation and mechanical testing approaches for a reliable assessment of the mechanical properties of glasses still remain a big challenge. In the present work, a novel approach for site-specific preparation and quantitative in situ tensile testing of thin silica glass membranes in the transmission electron microscope is presented. Thereby, advanced focused ion beam techniques are used for the preparation of nanoscale dog bone shaped silica glass specimens suitable for in situ tensile testing. Small amounts of gallium are detected on the surface of the membranes resulting from redeposition effects during the focused ion beam preparation procedure. Possible structural changes of silica glass upon irradiation with electrons and gallium ions are investigated by controlled irradiation experiments, followed by a structural analysis using Raman spectroscopy. While moderate electron beam irradiation does not alter the structure of silica glass, ion beam irradiation results in minor densification of the silica glass membranes. In situ tensile testing of membranes under electron beam irradiation results in distinctive elongations without fracture confirming the phenomenon of superplasticity. In contrast, in situ tensile testing in the absence of the electron beam reveals an elastic/plastic deformation behavior, and finally leads to fracture of the membranes. The Young’s moduli of the glass membranes pulled at beam off conditions in the TEM are comparable with values known for bulk fused silica, while the tensile strength is in the range of values reported for silica glass fibers with comparable dimensions. The impact of electron beam irradiation on the mechanical properties of silica glass membranes is further discussed. The results of the present work open new avenues for dedicated preparation and nanomechanical characterization of silica glasses, and further contribute to a fundamental understanding of the mechanical behavior of such glasses when being scaled down to the nanometer regime.

Improvement in mechanical and thermal properties of unsaturated polyester- based hybrid composites

Polymer matrix composites are used in automobile, structure and aerospace industries due to their light weight and high strength. The present research has an aim to reinforce locally developed silica nanoparticles and glass fibers in unsaturated polyester to produce polymer-based hybrid composites. Composites were synthesized by hand lay-up method with 1, 2, 3 and 4 wt% of silica sand nanoparticles and glass fiber. Mechanical tests like tensile, impact and micro-hardness were performed on the obtained polymer hybrid composites. The results of mechanical properties of the hybrid polymer matrix composites revealed an increasing trend. The SEM analysis was performed on the developed and fractured tensile testing samples. The SEM analysis showed the presence of silica nanoparticles in the samples and pulling action of fibers were seen under fractured tensile tests. The pulling actions of fibers from polymer matrix delayed the fractured mechanism and enhanced the mechanical properties. Silica nanoparticles filled the cavities generated during tensile test and extensive enhancement was revealed in tensile as well as impact energy. Toughness of the hybrid composite was also enhanced as a result. The thermal properties of the hybrid polymer composites were analyzed using thermogravimetric analysis. Thermal stability of the composite has been marginally increased with increasing wt% of reinforcement.

Proton therapy dosimetry using the scintillation of the silica fibers.

We investigate the feasibility of proton therapy dose measurement by using scintillation of a bare silica glass fiber. The emission spectra of the optical fiber at various depths in tissue-mimicking phantoms, irradiated with proton beams of energies 100-225MeV show two distinct peaks at 460 and 650nm whose nature is connected with the silica point defects. Our experimental results and Monte Carlo simulation showed that the Čerenkov radiation cannot be responsible for such a phenomenon. We showed that the intensity of the peak at 650nm correlates with the proton dose with a minimal effect of ionization quenching, while the intensity peak at 460nm under-reports the radiation dose.

Low-Coherence Interferometric Fiber-Optic Sensors with Potential Applications as Biosensors.

Fiber-optic Fabry-Pérot interferometers (FPI) can be applied as optical sensors, and excellent measurement sensitivity can be obtained by fine-tuning the interferometer design. In this work, we evaluate the ability of selected dielectric thin films to optimize the reflectivity of the Fabry-Pérot cavity. The spectral reflectance and transmittance of dielectric films made of titanium dioxide (TiO2) and aluminum oxide (Al2O3) with thicknesses from 30 to 220 nm have been evaluated numerically and compared. TiO2 films were found to be the most promising candidates for the tuning of FPI reflectivity. In order to verify and illustrate the results of modelling, TiO2 films with the thickness of 80 nm have been deposited on the tip of a single-mode optical fiber by atomic layer deposition (ALD). The thickness, the structure, and the chemical properties of the films have been determined. The ability of the selected TiO2 films to modify the reflectivity of the Fabry-Pérot cavity, to provide protection of the fibers from aggressive environments, and to create multi-cavity interferometric sensors in FPI has then been studied. The presented sensor exhibits an ability to measure refractive index in the range close to that of silica glass fiber, where sensors without reflective films do not work, as was demonstrated by the measurement of the refractive index of benzene. This opens up the prospects of applying the investigated sensor in biosensing, which we confirmed by measuring the refractive index of hemoglobin and glucose.

Evaluation of Mechanical and Insulation Properties of Nomex-T410 and HS Glass Polymer Matrix Composites

Glass fibre-reinforced plastics (GFRP) composite materials are extending the application horizons of designers in all branches of engineering. The present work is focused on development and determination of mechanical and dielectric properties of hybrid polymer composites of Nomex and High Silica Glass fabricated through handlay process. Five laminates each were fabricated for four different stacking orders with an average of 55% matrix contents. The polymeric composite was tested for mechanical and dielectric properties. It is found that the hardness was boosted in the laminate with the presence of more layers of High Silica glass fibers, presence of higher number of Nomex contributed for an increase in the compression strength and High Silica glass fibers and Nomex had an equal effect in increasing flexural strength of the composite. The Nomex and E-glass fibers present in the core of the composite covered by High Silica glass on the outer layer of the composite offered very good dielectric strength and surface resistivity for the composite and the absence of E-glass fibers have enhanced the dissipation factor. Further all laminates showed a greater stability towards chemical attack and temperature stability was observed up to 300° C.

Bismuth-doped germanate glass fiber fabricated by the rod-in-tube technique

Bismuth (Bi)-doped laser glasses and fiber devices have aroused wide attentions due to their unique potential to work in the new spectral range of 1 to 1.8 μm traditional laser ions, such as rare earth, cannot reach. Current Bi-doped silica glass fibers have to be made by modified chemical vapor deposition at a temperature higher than 2000°C. This unavoidably leads to the tremendous loss of Bi by evaporation, since the temperature is several hundred degrees Celsius higher than the Bi boiling temperature, and, therefore, trace Bi (∼50 ppm) resides within the final product of silica fiber. So, the gain of such fiber is usually extremely low. One of the solutions is to make the fibers at a temperature much lower than the boiling temperature of Bi. The challenge for this is to find a lower melting point glass, which can stabilize Bi in the near infrared emission center and, meanwhile, does not lose glass transparency during fiber fabrication. None of previously reported Bi-doped multicomponent glasses can meet the prerequisite. Here, we, after hundreds of trials on optimization over glass components, activator content, melting temperature, etc., find a novel Bi-doped gallogermanate glass, which shows good tolerance to thermal impact and can accommodate a higher content of Bi. Consequently, we successfully manufacture the germanate fiber by a rod-in-tube technique at 850°C. The fiber exhibits similar luminescence to the bulk glass, and it shows saturated absorption at 808 nm rather than 980 nm as the incident power becomes higher than 4 W. Amplified spontaneous emissions are observed upon the pumps of either 980 or 1064 nm from germanate fiber.

An Experimental Study on Self Consolidating Concrete with Silica Fume and Glass Fibre

An Experimental Study on Self Consolidating Concrete with Silica Fume and Glass Fibre

Optical decoherence and spectral diffusion in an erbium-doped silica glass fiber featuring long-lived spin sublevels

Understanding decoherence in cryogenically-cooled rare-earth-ion doped glass fibers is of fundamental interest and a prerequisite for applications of these material in quantum information applications. Here we study the coherence properties in a weakly doped erbium silica glass fiber motivated by our recent observation of efficient and long-lived Zeeman sublevel storage in this material and by its potential for applications at telecommunication wavelengths. We analyze photon echo decays as well as the potential mechanisms of spectral diffusion that can be caused by coupling with dynamic disorder modes that are characteristic for glassy hosts, and by the magnetic dipole-dipole interactions between $Er^{3+}$ ions. We also investigate the effective linewidth as a function of magnetic field, temperature and time, and then present a model that describes these experimental observations. We highlight that the operating conditions (0.6 K and 0.05 T) at which we previously observed efficient spectral hole burning coincide with those for narrow linewidths (1 MHz) { an important property for applications that has not been reported before for a rare-earth-ion doped glass.

Temperature sensitivity of chromatic dispersion in nonlinear silica and heavy metal oxide glass photonic crystal fibers

In this paper we report on the examination of the temperature influence of the effective refractive index and on the dispersion characteristics in air-hole lattice photonic crystal fibers. We use an original method to measure the temperature influence on chromatic dispersion in an optical fiber, where both the thermal expansion of the fiber and its effective group refractive index are taken into account. We present the experimental and modeling results of dispersion characteristics for two types of non-linear fibers, a silica glass fiber and a soft glass fiber in the temperature range from 20°C to 420°C. We measured the zero dispersion wavelength shift of + 0.020 nm/°C for the fused silica fiber and + 0.045 nm/°C for the heavy metal oxide soft glass fiber. Experimental results are in agreement with numerical modeling. Finally, the influence of the temperature-induced change of the dispersion profile on nonlinear performance of the studied fiber structures is investigated numerically. Notable change of parametric gain maxima locations is observed even for small changes of the zero dispersion wavelength in relation to the pump laser wavelength in a four-wave mixing fiber-based wavelength conversion scenario.

Effect of fiber stretch on quasi-phase-matching for second-harmonic generation in thermally poled twin-hole silica-glass fiber

Optimization of the quasi-phase-matching (QPM) for second-harmonic generation in thermally-poled twin-hole fiber was performed by stretch of the fiber. The periodic structure for QPM was fabricated by erasure of the second-order nonlinearity by exposure with ultraviolet light through a mask. Exposures with a KrF excimer laser and a low-pressure mercury lamp were compared. The fundamental-wave source was a Q-switched Nd:YAG laser. The dependence of the second-harmonic output on the strain induced by the stretch of the fiber was measured. For periodic depoling by excimer-laser exposure, the second-harmonic power increased by a factor of up to 4 by the stretch. For periodic depoling by mercury-lamp exposure, the maximum increase by the stretch was also by a factor of up to 4. The fiber stretch was effective for fine tuning of QPM for poled fibers.

Suppression of photo-darkening effect in Yb-doped silica glass fiber by co-doping of group 2 element

We found that co-doping of group 2 element effectively suppresses the photo-darkening (PD) effect in Yb-doped silica glass fiber and Mg co-doped Yb-doped silica glass fiber (YbMgSGF) is the most effective. This phenomenon is well understood on the basis of bond valence concept in the glass. In our model, Mg2+ ion with Al3+ stabilizes Yb3+ valence state with charge compensation in the silica glass and Mg2+ could smoothly match silica glass network because the ionic radius is the closest to the radii of Al3+ and Si4+. YbMgSGF is not only a promising Yb-doped optical fiber for high power fiber laser, but also for ultimate short length fiber lasers. This technique could also be applied to reduce PD effect in the other rare-earth ion doped fibers, such as Tm, Tb, Eu, and Sm.

Yb-doped silica glass and photonic crystal fiber based on laser sintering technology

We demonstrate the fabricating method for Yb3+-doped silica glass and double-cladding large mode area photonic crystal fiber (LMA PCF) based on laser sintering technology combined with a liquid phase doping method. The doped material prepared shows the amorphous property and the hydroxyl content is approximately 40 ppm. The attenuation of the fabricated LMA PCF is 14.2 dB m−1 at 976 nm, and the lowest value is 0.25 dB m−1 at 1200 nm. The laser slope efficiency is up to 70.2%.

Efficient and long-lived Zeeman-sublevel atomic population storage in an erbium-doped glass fiber

Long-lived population storage in optically pumped levels of rare-earth ions doped into solids, referred to as persistent spectral hole burning, is of significant fundamental and technological interest. However, the demonstration of deep and persistent holes in rare-earth ion doped amorphous hosts, e.g. glasses, has remained an open challenge since many decades -- a fact that motivates our work towards a better understanding of the interaction between impurities and vibrational modes in glasses. Here we report the first observation and detailed characterization of such holes in an erbium-doped silica glass fiber cooled to below 1 K. We demonstrate population storage in electronic Zeeman-sublevels of the erbium ground state with lifetimes up to 30 seconds and 80\% spin polarization. In addition to its fundamental aspect, our investigation reveals a potential technological application of rare-earth ion doped amorphous materials, including at telecommunication wavelength.

Nonlinear Elasticity of Silica Glass

In situ Brillouin light scattering measurements with a spatial resolution of ~1 μm have been carried out to study the elastic moduli of silica glass fibers in a single two‐point bend experiment to nominal strains of 7% in both tensile and compressive regions. Such data are necessary in order to convert the failure strains obtained from two‐point bend experiments into failure stress. For the first time, the neutral axis shift in a bent silica glass fiber was observed in our measurements, with more of the fiber deforming in compression than in tension, resulting from the nonlinear elastic behavior of silica glass. Understanding the neutral axis shift will improve the accuracy of strain and stress calculations in bent fibers. This study shows that an expression including a fifth‐order term is required to capture both the minimum in compression and the maximum in tension in the strain‐dependent Young's modulus of silica glass. A stress versus strain relation over a broad range of compressive and tensile strains was established for silica glass in this study, which will significantly improve our understanding of its deformation behavior.