Optical properties and local structure of Dy^(3+)-doped chalcogenide and chalcohalide glasses

Dy^3＋-doped Ge-Ga-Se chalcogenide glasses and GeSe2-Ga2Se3-CsI chalcohalide glasses were prepared. The absorption, emission properties, and local structure of the glasses were investigated. When excited at 808 nm diode laser, intense 1.32 and 1.55 μm near-infrared luminescence were observed with full width at half maximum （FWHM） of about 90 and 50 nm, respectively. The lifetime of the 1.32 μm emission varied due to changes in the local structure surrounding Dy^3＋ ions. The longest lifetime was over 2.5 ms, and the value was significantly higher than that in other Dy^3＋-doped glasses. Some other spectroscopic parameters were calculated by using Judd-Ofelt theory. Meanwhile, Ge-Ga-Se and GeSe2-Ga2Se3-CsI glasses showed good infrared transmittance. As a result, Dy^3＋-doped Ge-Ga-Se and GeSe2-Ga2Se3-CsI glasses were believed to be useful hosts for 1.3 μm optical fiber amplifier.

Structure of Bi_2O_3-ZnO-B_2O_3 system low-melting sealing glass

Bi2O3-ZnO-B2O3 system glass is a kind of lead-free low melting sealing glasses. The structure of Bi2O3-ZnO-B2O3 system low-melting sealing glass was investigated by DSC, FT-IR, XRD and SEM. The results show that with the increase of B2O3 content, the transition temperature Tg and softening temperature Tf of Bi2O3-ZnO-B2O3 system low-melting sealing glasses increase, which leads to the liquid phase precipitation temperature increasing and promotes the structure stability in the glass. With increasing the heat treatment temperature, a large number of liquid phases appear in samples and the sinter efficiency of the samples increases. The FT-IR spectra of the glasses show the presence of some bands that are assigned to vibrations of Bi--O bond from [BO3] pyramidal and [BiO6] octahedral units and B--O from [BO3] and [BO4] units. With the decrease of B203 content, the crystallization tendency of the glass increases. In glass samples Bl and B〉 crystallization starts at 460 ℃ and 540 ℃, respectively. Both of them precipitate Bi24B2O39 phases.

Visible to deep ultraviolet range optical absorption of electron irradiated borosilicate glass

To study the room-temperature stable defects induced by electron irradiation, commercial borosilicate glasses were irradiated by 1.2 MeV electrons and then ultraviolet（UV） optical absorption（OA） spectra were measured. Two characteristic bands were revealed before irradiation, and they were attributed to silicon dangling bond（E＇-center） and Fe^3＋species,respectively. The existence of Fe3＋was confirmed by electron paramagnetic resonance（EPR） measurements. After irradiation, the absorption spectra revealed irradiation-induced changes, while the content of E＇-center did not change in the deep ultraviolet（DUV） region. The slightly reduced OA spectra at 4.9 eV was supposed to transform Fe3＋species to Fe^2＋species and this transformation leads to the appearance of 4.3 eV OA band. By calculating intensity variation, the transformation of Fe was estimated to be about 5% and the optical absorption cross section of Fe2＋species is calculated to be 2.2 times larger than that of Fe^3＋species. Peroxy linkage（POL, ≡Si–O–O–Si≡）, which results in a 3.7 eV OA band, is speculated not to be from Si–O bond break but from Si–O–B bond, Si–O–Al bond, or Si–O–Na bond break. The co-presence defect with POL is probably responsible for 2.9-eV OA band.

Surface roughness prediction model in ultrasonic vibration assisted grinding of BK7 optical glass

Pre-knowledge of machined surface roughness is the key to improve whole machining efficiency and meanwhile reduce the expenditure in machining optical glass components.In order to predict the surface roughness in ultrasonic vibration assisted grinding of brittle materials,the surface morphologies of grinding wheel were obtained firstly in the present work,the grinding wheel model was developed and the abrasive trajectories in ultrasonic vibration assisted grinding were also investigated,the theoretical model for surface roughness was developed based on the above analysis.The prediction model was developed by using Gaussian processing regression(GPR)due to the influence of brittle fracture on machined surface roughness.In order to validate both the proposed theoretical and GPR models,32sets of experiments of ultrasonic vibration assisted grinding of BK7optical glass were carried out.Experimental results show that the average relative errors of the theoretical model and GPR prediction model are13.11%and8.12%,respectively.The GPR prediction results can match well with the experimental results.

Optical temperature sensor based on up-conversion fluorescence emission in Yb^(3+):Er^(3+) co-doped ceramics glass

yb^3＋：Er^3＋ co-doped oxy-fluoride ceramics glass has been prepared. The mechanism of up-conversion emissions about Er^3＋ was discussed, and the temperature properties of green up-conversion fluorescence between 303 and 823 K were investigated. The results show that the sensitivity of this sample reaches its maximum value, about 0.0047 K^-1, when the temperature is 383 K, indicating that this kind of sample can be used as high temperature and high sensitivity optical temperature sensor.

Fabrication,microstructure,and optical properties of nanocrystalline transparent LAST glass ceramics containing CeO_2

In the present research, the effect of CeO2 dopant on the fabrication of transparent lithium aluminosilicate titanate （LAST） glass ceramics was investigated. Nanocrystallineβ-quartz solid solution （s.s.） was observed to be the main phase crystallized in this system. Com-parable refractive indices of the glassy matrix andβ-quartz s.s., as well as the incorporation of very fine grains size were determined as the main reasons for retaining the transparency of the glass ceramics. CeO2 was introduced as a suitable optical agent, playing a role as a network modifier in the glass ceramics, because it does not accelerate the growth process and retards the extended growth of crystals. Optical investi-gations indicate that the Fermi energy level, direct and indirect band gaps, and Urbach energy decrease with increasing nanocrystal content in the glassy matrix of specimens, which can be related to the expansion of conduction band, the enhancement of ionic bonds in the crystal lat-tice, and the enhancement of structural arrangement degree, respectively.

Effect of SrO Content on Structure,Thermal Properties and Chemical Stability of Bi2O3-B2O3-ZnO-SrO Low-melting Glass for Si-Al Alloy Package

The 40Bi2O3-30B2O3-(30-x)ZnO-xSrO (x=0-15mol%,BBZSr) glass system was prepared by the conventional melt quenching method.The effect of SrO addition on structure,thermal properties,chemical stability and sealing performance of BBZSr glass were investigated thoroughly.The experimental results show that the total proportions of [BO3] group and [BO4] group decrease and the vibrations of [BiO3] group and [BiO6] group become weaker with the increase of SrO addition content,suggesting the glass network structure is strengthened owing to the SrO addition.Hence,both the thermal and chemical stability were significantly improved as the SrO content was increased.When the SrO content increased from 0 to 15mol%,the glass transition temperature and softening temperature slightly increased from 380 to 388 ℃ and from 392.7 to 402.2 ℃,respectively,meanwhile the coefficient of thermal expansion also increased from 10.49×10^-6 to 11.16×10^-6/℃ (30-300 ℃).The BBZSr glass with 15mol% SrO exhibited excellent comprehensive properties with low glass transition temperature(384.9 ℃),low softening temperature(400.3 ℃),high coefficient of thermal expansion (11.14×10^-6 ℃,30-300 ℃),good thermal and chemical stability.Besides,the glass had the good wetting behavior and sealing performance for Al-50%Si alloy.

An optical glass plane angle measuring system with photoelectric autocollimator

Optical glass is the most widely used optical material.It is necessary to measure its geometric characteristic quickly and reliably to meet the quality of optical glass.A vision measuring system combining photoelectric autocollimation system with high-precision rotary stage is designed to measure the parallelismand angle of optical glass plane.A novel method is proposed to overcome the difficulty ofmeasuring parallelismof optical glass.The model of parallelism and angle measurement is established and the feasibility is analyzed.The image processing algorithm combining Steger algorithm with the least square method is selected.The uncertainty of angle measurement system for angle measurement is 3.0″.The system can solve the problem of measuring the angle of optical glass with high precision and has important significance for optical system.

Effects of Nb2O5 on thermal stability and optical properties of Er^3＋-doped tellurite glasses

Er^3＋-doped tellurite glasses with molar compositions of xNb2O5 - （14.7 - x）Na2O-10ZnO-5K2O-10GeO260TeO2-0.3Er2O3 （x = 0, 3, 5, 7 and 9） have been investigated for developing 1.5 μm fibre and planar amplifiers. The effects of Nb2O5 on the thermal stability and optical properties of Er^3＋-doped tellurite glasses have been discussed. It is noted that the incorporation of Nb205 （x=5） increases the thermal stability of tellurite glasses significantly. Er^3＋-doped niobium tellurite glasses exhibit a large stimulated emission cross-section （7.2×10^-21 - 10.7×10^-21 cm^2） and the gain bandwidth, FWHM×σ^peak （274 ×10^-28 - 480×10^-28 cm^3）, which are significantly higher than that of silicate and phosphate glasses. In addition, the intensity of upconversion luminescence of the Er3＋-doped niobium tellurite glasses decreases rapidly with increasing Nb2O5 content. As a result, Er^3＋-doped niobium tellurite glasses might be a potential candidate for developing laser or optical amplifier devices.

Deformation Analysis of Micro/Nano Indentation and Diamond Grinding on Optical Glasses

The previous research of precision grinding optical glasses with electrolytic in process dressing （ELID） technology mainly concentrated on the action of ELID and machining parameters when grinding, which aim at generating very ＂smoothed＂ surfaces and reducing the subsurface damage. However, when grinding spectrosil 2000 and BK7 glass assisted with ELID technology, a deeply comparative study on material removal mechanism and the wheel wear behaviors have not been given yet. In this paper, the micro/nano indentation technique is initially applied for investigating the mechanical properties of optical glasses, whose results are then refereed to evaluate the machinability. In single grit diamond scratching on glasses, the scratching traces display four kinds of scratch characteristics according to different material removal modes. In normal grinding experiments, the result shows BK7 glass has a better machinability than that of spectrosil 2000, corresponding to what the micro/nano indentation vent revealed. Under the same grinding depth parameters, the smaller amplitude of acoustic emission （AE） raw signals, grinding force and grinding force ratio correspond to a better surface quality. While for these two kinds of glasses, with the increasing of grinding depth, the variation trends of the surface roughness, the force ratio, and the AE raw signals are contrary, which should be attributed to different material removal modes. Moreover, the SEM micrographs of used wheels surface indicate that diamond grains on the wheel surface after grinding BK7 glass are worn more severely than that of spectrosil 2000. The proposed research analyzes what happened in the grinding process with different material removal patterns, which can provide a basis for producing high-quality optical glasses and comprehensively evaluate the surface and subsurface integrity of optical glasses.

Glass Formation and Optical Band Gap Studies on Bi_2O_3-B_2O_3-BaO Ternary System

The glass forming region of Bi2O3-B2O3-BaO ternary system was investigated. A serial of glass samples with high Bi2O3 content in Bi2O3-B2O3-BaO system were prepared by using conventional melting and quenching meld, and the refractive indexes and absorption spectra of samples were measured. It is found that the refractive index of samples as well as the UV absorption increase with the increase of BaO content. According to the Tauc law, optical band gap Eopg which is assumed to be the effective energy band gap Eg is calculated and decreases with the increasing BaO content, and the ratio of Eg/Eopg is 1.3.

Optical Spectroscopy of Er^(3+) and Er^(3+)/Yb^(3+)Co-doped Bi_2O_3-GeO_2-B_2O_3-ZnO Glasses

The （60 - x）Bi2O3 - xGeO2-30B2O3-10ZnO （x = 5, 10, 20, 30 molar percent） glasses doped with Er^3＋ and Er^3＋/Yb^3＋ were fabricated using the melting method. The thermal stability of the glasses was studied with their DTA curves. The results show that the difference between the glass transition temperature and the crystallization onset temperature increases with the increase of GeO2 content, indicating that the thermal stability of the glass has become better. The absorption spectra were recorded and the stimulated emission cross sections were calculated using the McCumber theory. The Ω2, O4, and Ω6 parameters,the transition probability, the radiative lifetime, and the fluorescence branch ratio of Er^3＋ for optical transition were calculated from their absorption spectra in terms of reduced matrix U^（t）（λ = 2, 4, 6） character for optical transitions. The infrared emission of Er^3＋ was measured upon excitation with 970 nm light and the full width at half-maximum （FWHM） was estimated from the emission spectra. The pumping efficiency and the intensity of the emission at the 1.54 μm band of Er^3＋ were enhanced considerably by co-doping Yb^3＋ .

Preparation and Characterization of Low-melting Glasses Used as Binder for Protective Coating of Steel Slab

The low-melting phosphate glass was prepared for production of glass binders for protective coating of steel slab. Effects of different O/P ratios on glass structures and properties were analyzed. Differential thermal analysis （DTA） and infrared spectroscopy （IR） techniques were applied for low-melting glass binder. It was found that the glass transition temperature（T） was about 300 ℃ and softening temperature（T1） was about 480 ℃. The choice of O/P ratio was very important to the glass transition and softening temperatures. When more P=O bonds existed in the glass networks, P-O-P bond angle was deformed with decreasing of the ratio of O/E The coatings could adhere to the substrates instantaneously at 800 ℃ when the content of binder exceeded 3wt%. The optimal content of glass binder was 5wt%.

Optical Basicity and Polarizability of Nd³⁺-Doped Bismuth Borate Glasses

This paper reports on different physical and optical properties of Nd3+-doped bismuth borate glasses. The glasses containing Nd3+ in (25 - x)Bi2O3:20Li2O:20ZnO:35B2O3:xNd2O3 (where x = 1, 1.5, 2 mol%) have been prepared by melt-quenching method. The amorphous nature of the glasses was confirmed by X-ray diffraction studies. The physical parameters like dielectric constant, refractive index, ionic concentration, oxygen-packing density, inter ionic distance, polaronradius, reflection loss, energy gap, molar refractivity, molar polarizability, electronic polarizability, optical basicity and field strength are computed. On the basis of the measured values of the density and refractive index, the Nd3+ ion concentration in glasses, the polarizability of oxide ions and optical basicity were theoretically determined. The theoretical value of average electronic polarizability and oxide ion polarizability were calculated by using Lorentz-Lorenz formula. Theoretical optical basicity of the glasses is evaluated based on equation proposed by Duffy and Ingram. The metallization criterion has also been calculated on the basis of refractive index and energy gap. The large value of metallization criterion indicates that the glass materials are insulators. The results obtained predict the nature of bonding in the present glasses and provide basis for developing new nonlinear optical material.

Simulation and Experiment of Double Grits Interacting Scratch for Optical Glass BK7

The elastic-plastic transition regime and brittle-ductile transition regime in scratch process for optical glass BK7 were analyzed based on the Hertzian equation and the stress ratio theory which was proposed by Wei. The interacting scratch process for optical glass BK7 with the grit interval distance as the variable was simulated by the ABAQUS software of finite element simulation based on the energy fracture theory. Double grits interacting scratch test for optical glass BK7 was carried out on the DMG ULTRASONIC 70-5 linear, by which the reliability of finite element simulation was verified. The surface morphology of the workpiece was analyzed by scanning electron microscopy（SEM）, which showed that the width of groove increased obviously with the increase of scratch depth and the grit interval distance. Results of the width of groove were consistent with the simulation results. The subsurface damage layer was analyzed by the method of HF acid etching, which showed that there was an area of cracks intersecting. The scratching force was measured by the threedimensional dynamometer of KISTLER, which showed that the second scratching force increased with the increase of scratching depth and the grit interval distance. The force in the second scratch was smaller than that in the first time, which was consistent with the Griffith fracture theory.

Direct microwelding of dissimilar glass and Kovar alloy without optical contact using femtosecond laser pulses

In the current microwelding process using femtosecond(fs) laser between dissimilar materials,surface polishing and pressure assistance,so-called optical contact,are believed necessary.In this paper,direct welding of soda lime glass and Kovar alloy using a fs laser is investigated to overcome the limit of optical contact.The processing of fs laser welding is comprehensively studied by varying the laser power,welding velocity and the number of welding.The shear joining strength is as high as 2 MPa.The cross-section of glass-Kovar alloy joints,the elemental diffusion and the fracture behavior of welded joints were studied.The results show that the fs laser irradiates the surface of Kovar alloy,micron/nanometer-sized metal particles are generated.These particles perform the role as an adhesive part in the welding process.It is believed that the Si atoms diffuses to Kovar alloy from the glass and partially replaces the Fe^(2+) ions on the surface of Kovar alloy,indicating that the mixing and interdiffusion of materials have occurred during the welding process.Finally,the welded sample was tested and has excellent water resistance and sealing property.Furthermore,to justify that this method can be applied to other stack ups,the glass-copper,the glass-Al6063 and sapphire-ceramic are also welded together.This work greatly simplifies the fs laser microwelding process and promotes its industrial applications,such as optoelectronic devices,medical devices and MEMS.

Optical Band Gap, Oxidation Polarizability, Optical Basicity and Electronegativity Measurements of Silicate Glasses Using Ellipsometer and Abbe Refractometer

The values of refractive index (n) for silicate glasses (silica, soda lime and borosilicate 7059) are decreased from 1.5119 to 1.5111, 1.5086 to 1.5065 and 1.5296 to 1.5281, respectively;and the optical band gap (Eg) is increased from 9.8 to 9.81 eV, 9.845 to 9.88 eV and 9.56 to 9.58 eV, respectively over the temperature range 295 - 473 K using ellipsometer at wavelength 632.8 nm. While n is decreased from 1.5276 to 1.5274, 1.5074 to 1.5070 and from 1.5283 to 1.5281, respectively;and Eg is increased from 9.59 to 9.592 eV, 9.862 to 9.870 eV, and 9.574 to 9.58 eV, respectively over the temperature range 297 - 322 K using Abbe refractometer at wavelength 589.3 nm. The values of oxide ion polarizability [αo2- (n) and αo2-(Eg)] regarding silica, soda lime and borosilicate 7059 glasses are decreased from 1.3427 to 1.3408, 1.6014 to 1.5941, 1.4329 to 1.4193, respectively over the temperature range 295 - 473 K using ellipsometer;and are decreased from 1.3786 to 1.3764, 1.5991 to 1.5969, 1.4297 to 1.4191, respectively over the temperature range 297 - 322 K using Abbe refractometer. Similarly, the values of optical basicity [A (n) and A (Eg)] of silica, soda lime, and borosilicate 7059 glasses are decreased from 0.4272 to 0.4245, 0.6271 to 0.6224, 0.5045 to 0.4933, respectively over the temperature range 295 - 473 K using ellipsometer;and are decreased from 0.4586 to 0.4567, 0.6256 to 0.6242, 0.5018 to 0.4930, respectively over the temperature range 297 - 322 K using Abbe refractometer. Further, we have found that for silica, soda lime and borosilicate 7059, the values of electronegativity (ξ1av) QUOTE ζ1av) using Zahidnumerical model [based on αO2- (n) and A (n)] are increased from 5.1035 to 5.5504, 4.0393 to 4.830, 4.8143 to 5.0111, respectively over the temperature range 295 - 473 K using ellipsometer;while these values are increased from 5.0657 to 5.2149, 5.0657 to 5.2149, 4.8357 to 5.0111, respectively over the temperature range 297 - 322 K using Abbe refractometer. It is very clear from this research report that both refractive index and optical band gap-based-oxide ion polarizability and optical basicity have the same decreasing trend as the temperature is increased, and this trend indicates that the reported glasses have a very small amount of electronic polarizability. Moreover, this decreasing trend occurs due to the decreasing amount of non-bridging oxygen (NBO) which in turn caused a decrease in refractive index within the silicate glass system at higher temperature. Since the calculated values of electronegativity are found to be in the range 4.0393 - 5.5504 for the reported silicate glasses, so all these glasses have an ionic character. Moreover, low values of optical basicity and of oxide ion polarizability suggest that the silicate glasses are not novel glasses (optical functional glasses) for non-linear optical (NLO) devices or for three dimensional displays.

Scratching and Turning Experiments on Machinability of Optical Glass SF6 in Diamond Cutting Process

To improve the machinability of optical glass and achieve optical parts with satisfied surface quality and dimensional accuracy, scratching experiments with increasing cutting depth were conducted on glass SF6 to evaluate the influence of cutting fluid properties on the machinability of glass. The sodium carbonate solution of 10.5% concentration was chosen as cutting fluid. Then the critical depths in scratching experiments with and without cutting fluid were examined. Based on this, turning experiments were carried out, and the surface quality of SF6 was assessed. Compared with the process of dry cutting, the main indexes of surface roughness decrease by over 70% totally. Experimental results indicated that the machinability of glass SF6 can be improved by using the sodium carbonate solution as cutting fluid.

Evaluation of Correction Algorithm for the Reflectance Measured with Optical Glass

The proposed algorithm for reflectance measured with optical glass has been verified with materials of various forms. The reflectances measured with optical glass ( raw), without glass (true) and corrected by the algorithm are compared. The results show that the corrected reflectance agrees very well with true one and their color differences fall below the acceptable limit, which indicates the validity of the correction algorithm. The algorithm could be used not only for fiber-forming materials, but also for powder-forming, granulate-forming, etc.

A New Faraday Rotation Measurement Method for the Study on Magneto Optical Property of PbO-Bi₂O₃-B₂O₃Glasses for Current Sensor Applications

MAGNETO-OPTICAL current transformers (MOCT) based on the Faraday Effect provide numerous advantages over the conventional transformers. However the commonly used materials in MOCT are crystals that are very expensive and temperature dependence thus will cause many problems for the output signal. Cost efficient diamagnetic PbO-Bi2O3-B2O3 (PBB) glass system is fabricated in this study, for the aim of obtaining a good candidate glass with high verdet constant and good temperature resistance to replace crystals. A home-made optical bench was setup, calibrated and used for measuring the verdet constant of the fabricated glasses. Glass with composition of 50%PbO-40%Bi2O3-10%B2O3 in mol showed high Verdet constant (0.1533 min/Gauss.cm) and good value of the figure of merit (0.02635 min/Gauss), which can be considered as the ideal candidate for MOCT applications.