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Optical glass BK7 is widely used in optical lenses. It is a kind of hard and brittle material and thus difficult to machine. To solve the problems it has encountered in terms of polishing efficiency and quality, the axial ultrasonic vibration assisted polishing (UVAP) method is adopted in this study. A mathematical-prediction-model, firstly considering the effects of periodically changing pressure caused by ultrasonic vibration, is developed to predict the generated surface-profile. And for the first time, the concept of “Preston-coefficient distribution-function” is proposed to describe the effect of the abrasive-particle distribution on material-removal distribution-function. A series UVAP experiments on optical glass BK7 at different polishing parameters are conducted to validate the polishing efficiency and feasibility of the developed prediction model and proposed concept. The results confirm that UVAP method can realize a higher material removal rate (MRR) and a better surface quality. Compared to conventional method, the predictions are in good agreement with the experiments. The comparison of the obtained surface profiles proves the benefits of ultrasonic vibration as well. Moreover, the research results can be used to guide the adjustment of polishing parameters for deterministic material removal in straight feeding process of UVAP, and provide a valuable basis for trajectory planning of the global polishing of workpiece surfaces.

Optical glass must satisfy multiple specifications for a given optical instrument. Machine learning has recently been applied to the development of materials. The optimization of compositions with multiple target properties has been investigated. Here, we focus on the trade-off between target properties, namely the refractive index nd and the Abbe number νd, for optical glass and apply a multi-objective Bayesian optimization algorithm called ParEGO to find glass compositions with low target property values using INTERGRAD data. In addition, we examine the effects of normalizing the target properties and descriptors on the search performance of ParEGO. The results reveal that ParEGO can effectively find compositions with low target property values and that normalization is necessary for sufficient ParEGO search performance. The normalization of target properties and descriptors may be effective for other multi-objective Bayesian optimization algorithms and materials. We also discuss how to apply the method to the actual development of optical glass.

Crack initiation, propagation and interaction during single and double scratch testing are investigated at a constant load under different tool apex angles to understand the influence of tool apex angle on the material removal process of optical glass BK7. During the single scratch test, a large number of fragmentized and rambled shallow lateral cracks and radial cracks occur when the tool apex angle is small. As the tool apex angle increases, the number of shallow lateral cracks and radial cracks decreases, and the lateral cracks become more continuous. Radial cracks have curved paths under the surface and can lead to chippings independently. In addition, radial cracks can facilitate the deeper spreading of shallow lateral cracks. During the double scratch test, the interaction between radial cracks and the 2nd lateral cracks in the middle zone and three kinds of unique cracks, namely, extended lateral cracks, shallower 2nd lateral cracks and deeper radial cracks, are found when the tool apex angle and separation distance are both small. Finally, the material removal volume in the double scratch test is measured in terms of different tool apex angles and separation distances.

This work focuses on studying the impact of process parameters on the machining performance of rotary ultrasonic drilling of BK-7 glass and improving the machining efficacy by simultaneous optimization of conflicting output responses using utility approach. Taguchi based L9 array has been employed for framing the experimental work and to optimize output characteristics individually. Feed rate, tool rotational speed and ultrasonic power have been elected to understand their impact on material removal rate (MRR) and surface roughness (SR). Analysis of means (ANOM) has been implemented on raw data to identify the % contribution of statistically significant factors. Utility approach has been executed for simultaneous optimization of performance attributes. Middle level of feed along with highest levels of tool rotation speed and ultrasonic power, were predicted as optimal solution for superior performance. Feed was found to have maximum impact on MRR and SR followed by tool rotation speed and ultrasonic power. All the predicted results agreed well with experimental results at 95% confidence level. SEM micrographs of machined surfaces showed the presence of plastically deformed regions at lower levels of feed; whereas higher feed led to dominance of brittle fracture. Further, SEM micrographs revealed the occurrence of grain pullout, grain fracture and bond fracture of lateral as well as end face of the tool. Keywords: Abrasive, Ultrasonic drilling, Utility, ANOM, Taguchi

Sand particles were characterized using the x-ray micro-CT technique yielding 3-D reconstructions to be used in peridynamic modeling of experiments presented in an earlier paper [1]. Impact experiments were conducted using sand microparticles and four distinct glass targets: alumino-boro-silicate, Pyrex, BK7, and fused silica. Incoming and rebound velocities, as well as particle volume, were calculated using high-speed video footage. Optical microscopy and scanning electron microscopy were used to characterize damage sites. Video footage was used to correlate specific damage sites to the sand particle that caused the damage. A sampling of these impact events were then modeled using bond-based peridynamics, generating voxel data for sand grid files from the x-ray micro-CT scans. In simulations, single impact events were modeled using multiple sand particle orientations to demonstrate the effect of particle shape on resulting damage. Peridynamic results were shown to have good correlation to experiments.

Optical glass which usually has specific optical constants is the basic material of optical system of optical instruments and optical machinery. In order to accurately calculate the optical constants of optical glass, two models (PTT method and PTR method) were established for the quartz glass taking quartz glass as the research object. The application range and precision of the two methods were compared, and the influence of transmittance deviation on the accuracy of the two methods was analyzed. Both of the two methods have wide application scope and high accuracy. Under the influence of transmittance deviation, the PTR method has higher precision in calculating refractive index and the PTT method has higher precision in calculating absorption index. Therefore, the two methods are complementary to each other in resisting transmittance deviation.

Optical glass scratching can induce various types of cracks, among which median cracks are extremely detrimental and penetrate deeply under the surface. Due to deep-scratching process complexity, it is challenging to devise a method to predict median crack depth. Indentation testing has been examined comprehensively in prior research works. It has been found that using the correlation between scratch and indentation testing can simplify predictive method development. In this research, a numerical method based on indentation testing is proposed to determine median crack depth during deep scratching. In the first step, an FE model is configured to simulate the indentation testing process and the Cohesive Zone Method is applied to describe median crack behavior. The cohesive parameters calibrated through experimental indentation testing are implemented in the FE scratch model, and the results are compared with the experimental scratch test results. According to the results, the FE scratch model was enhanced by mode II fracture energy and the modeled friction coefficient. The indentation and scratch experiments were conducted with BK7, F2, Fused silica, K5, Pyrex, Quartz, SF6, and SF19. The experimental results prove that the nonlinearity of the median crack depth curve correlates with KIc. A comparison of the experimental and numerical results demonstrates the model is virtually functional for materials with KIc below 1000 kPa m1/2. Comparisons between the current findings and other studies infer the model and experimental results are accurate and reliable.

The machining induced edge chipping of hole manufacturing restricts the productivity and design capability of products made from brittle materials. Rotary ultrasonic machining (RUM) has been sufficiently proved as a suitable approach for hole drilling in brittle materials with reduced cutting force and improved hole edge quality. However, apparent edge chipping is still an important restriction of RUM application. In this study, a compound step-taper tool for RUM was designed to further reduce the edge chipping defects via tool design. RUM tests on quartz glass were conducted to evaluate the effectiveness of the compound step-taper tool. The experimental results demonstrated that the compound tool could reduce the edge chipping size at the hole exit and entrance by 60%–80% and 35%–50%, respectively. The mechanism of edge chipping reduction at the hole exit is that cutting force decreased as the undrilled thickness decreased. This is due to the wedge-type contact structure between the tool’s taper face and the workpiece material. Furthermore, the edge chipping reduction at the hole entrance occurs because of the shielding effect of residual cracks. Residual cracks produced by the second outermost abrasives of the tool’s taper face suppressed the initiation and propagation of lateral cracks that were produced by the outermost abrasives of the tool’s taper face. Theoretical analysis indicated that the compound tool step is beneficial for guaranteeing the effectiveness of tool’s taper face.

Grinding process of optical glass has been reported to be related with the creation of subsurface cracks. However, for the time being, most measurement methods have been depended on human operations. In this paper, an intelligent assessment method based on image processing technique is proposed. Grinding trials proved that, the proposed method can accurately (with the biggest relative error of 3.53%) and quickly (nearly 1.6 seconds per micrographs) recognize and measure the subsurface crack depths. More importantly, the proposed method has good robustness to different-sized images. Besides, the method does not require any input parameters or any adjustment of thresholds, therefore the method does not require any prior knowledge of either mechanical grinding process or brittle material behaviors relating with subsurface cracks. Based on above, the proposed method is expected to be meaningful to both metrology equipment companies and optical glass manufacturers.

In this paper, the variable coefficients coupled Hirota equation is investigated by virtue of the unified method. Playing an important role in optics, the coupled Hirota equation describes the transmission process when high intensity ultra-short pulses pass through an optical glass fiber. Two types of complex wave solutions, polynomial function and rational function solutions, are gained. The polynomial function solutions incorporate complex solitary, complex soliton and complex elliptic wave solutions, while the rational function solutions involve complex periodic and complex soliton wave solutions. Furthermore, by choosing different values of the parameters, we illustrate the dynamical behaviors and the physical signification of these solutions.

Axial ultrasonic vibration end grinding (AUVEG) has been recognized as an efficient machining method for hard and brittle materials. In this paper, a theoretical model was proposed for predicting cutting force in AUVEG of BK7 optical glass with consideration of the nonuniform protrusion height of abrasive grits. Since the protrusion height of diamond grits was closely related to the cutting force, the modelling of the wheel end-face morphologies was performed to obtain the protrusion height information of diamond grits. Based on indention theory combined with energy perspective, a material removal rate model was proposed for establishing the cutting force model. Experiments were conducted to verify the validity of the proposed model, and the mean error between predicted and experimental force is 4.94%. The proposed model could be used in selecting process parameters for realizing high efficiency and precision AUVEG machining of BK7 optical glass.

Brittle material removal fraction (BRF) is defined as the area fraction of brittle material removed on machined surface. In the present study, a novel theoretical model of BRF was proposed based on indentation profile caused by intersecting of lateral cracks. The proposed model is related to surface roughness and the subsurface damage (SSD) depth of optical glass during precision grinding. To investigate the indentation profile, indentation tests of K9 optical glass were conducted using single random-shape diamond grains. The experimental results indicate that the indentation profile is an exponent function. To verify the proposed BRF model, BRF, surface roughness and SSD depth of K9 optical glasses were investigated by a series of grinding experiments with different cutting depths. The experimental results show that BRF is dependent on surface roughness and SSD depth. The relationship between BRF, surface roughness and SSD depth is in good accordance with the proposed theoretical model. The proposed BRF model is a reasonable approach for estimating surface roughness and SSD depth during precision grinding of optical glass.

In this paper, we propose a bi-ocular Head Up Display system using four lenses made up of two optical glass materials, which is compact and light weight. The initial component layout of the system is done using Petzval lens configuration and thin lens aberration formulae. To get rid of third and higher order aberrations rotational aspheric surfaces has been used.

Thin films of 1-pentyl-2 / ,3 / -difluoro-3 /// -methyl-4 //// -octyl- p -quinquephenyl and 9,10-Bis (4-pentylphenylethynyl)antracene organic molecules were grown on optical glass, silicon and porous silicon substrates. First optical and luminescent properties of such hybrid composites are thoroughly studied using spectroscopic techniques. The strong decrease of aggregation in thin films of 1-pentyl-2 / ,3 / -difluoro-3 /// -methyl-4 //// -octyl- p -quinquephenyl on porous silicon was observed. The possibility of simultaneous red, green and blue tunable photon emission from organic film/porous silicon hybrid structure is demonstrated.

Surface treatment of optical glass fibers is an effective method to clean the impurities and remove the damage layer, such as scratches caused by the cold processing. Optical losses at the fiber core/cladding interface can thereby be decreased. Using X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), we studied the surface composition and morphology of fluorophosphate (FP) glass after polishing and chemical etching. In addition, we investigated the etching mechanism and the optimal concentration of etching solution. Results show that the surface composition is very close to that of the bulk glass for some elements, and the root-mean-square (RMS) roughness is approximately 0.821 nm. A method including acid–alkali pretreatment and a second polishing step is a novel way to improve the smoothness of surface and to eliminate defects such as contaminants and scratches.

In this work different fibre optic sensors for the structural health monitoring of civil engineering structures are reported. A fibre optic crack sensor and two different fibre optic moisture sensors have been designed to detect the moisture ingress in concrete based building structures. Moreover, the degeneration of the mechanical properties of optical glass fibre sensors and hence their long-term stability and reliability due to the mechanical and chemical impact of the concrete environment is discussed as well as the advantage of applying a fibre optic sensor system for the structural health monitoring of sewerage tunnels is demonstrated.

Since thermal safety is a significant topic in Li-ion batteries (LIBs), monitoring the internal temperature can offer valuable information to clarify the mechanism of heat accumulation. However, it is a challenge to measure the internal temperature of LIBs due to the harsh electrochemical environment and unexpected impacts on the battery performance. For addressing such issue, a novel internal temperature measurement technique with a minimized influence on the electrochemical performance is developed for in situ measuring the internal temperature of the LIB. In the specific design, one end of the LIB is sealed with a BaF2 optical glass, through which the infrared camera is allowed for real-time monitoring the internal temperature during charging and discharging processes. In addition to a stable electrochemical performance in such the visualized LIB, the observation results indicate that the temperatures are different during the charging and discharging processes. A maximum temperature difference 2.0°C between internal and surface of the visualized LIB is observed at the end of discharge process under 2C rate condition. It indicates that internal temperature is more important to analyze the effects of temperature on the thermal safety of the high capacity LIBs. The proposed internal temperature measurement technique could be widely used for analyzing the effects of temperature on the thermal safety of LIBs in further work.

Reference materials (RM) for relative spectral correction of emission spectra and day-to-day sensitivity monitoring of spectrofluorimeters were developed. The 2 kinds of inorganic glass were used as RM material – custom developed Cu+ –ion doped phosphate glass and colored optical glass SZS-17 (blue-green). RM can be either cuvette-shaped or in the form of flat plate and installed in sample compartment of the instrument. Flat plate geometry allows to minimize the dependency of RM fluorescence intensity from the characteristics of instrument's optical circuit due to inner filter effect.

A simple and stable method based on a single-element interferometer for accurately measuring refractive index of transparent liquids was demonstrated. The refractive index is measured by rotating a rectangular optical glass cell which contains sample liquid and air simultaneously, and by calculating interference fringe shift number which is detected from an interferogram. This method was successfully used to measure the refractive indices of various transparent liquids including distilled water, ethanol and NaCl–water and ethanol–water solutions at various concentrations. The temperature- dependent refractive index of distilled water was also measured. Furthermore, our method is simple to implement, vibration insensitive, and of high accuracy up to 10−4.

This paper presents a series of micro-structured coarse-grained diamond wheels for optical glass surface grinding aiming to improve the grinding performance, especially subsurface damage. The 150 μm grit size, single layer electroplated diamond grinding wheels with different interval micro-groove arrays were manufactured by nanosecond pulsed laser, successfully. The influence of micro-structures on surface roughness and subsurface damage was investigated. Compared with conventional coarse-grained diamond wheel, the subsurface damage depth was reduced effectually from 5 to 1.5 μm, although the better surface roughness was not obtained by the micro-structured coarse-grained diamond wheel. In addition, the surface roughness and subsurface damage depth were both reduced with the decreasing interval of micro-groove arrays.

This study aims to determine the correlation between the contact surface, the polishing pressure and the friction coefficient during the optical glass polishing. For this purpose, BK7 optical glass samples were polished and the mentioned parameters were measured to find a correlation between them. Several methods of characterization have been used; the mechanical profilometer, the AFM, and in addition setups for measuring forces and the contact surface have been developed and adapted to the polishing machine. The found results have shown the existence of a close relationship between the three parameters and the influence of each other. This have allowed to deduce that during the polishing process it is very important to control the contact pressure and the polisher form according to the pressure distribution in order to guarantee a very high quality of the polished surface.

In this work, a polarization ray tracing method for dynamical-optical systems is analyzed, in order to get information about the influence of mechanical stresses in optical lenses on the ray propagation. Therefore, elastic multibody system calculations are combined with a polarization ray tracing method. If an optical lens is mechanically loaded, the resulting deformation causes mechanical stresses. Thus, the optical glass behaves anisotropic and inhomogeneous, which affects the ray refraction within the optical lens and the state of polarization of the light rays. These changes in the light rays behavior are considered in the presented polarization ray tracing method. In addition to stress-induced birefringence at the lens front and gradient-index ray tracing within the lens, the state of polarization can be traced through the optical lens using Jones vectors. A numerical example demonstrates the advantage of this ray tracing method over geometrical ray tracing for dynamical-optical systems.

We report on a simple processing procedure to retrieve the phase from spectral interferograms including a stationary-phase point. First, the numerical simulations are performed to demonstrate high precision of the phase retrieval from the spectral interferogram. Second, the feasibility of the procedure is confirmed in processing the experimental data from a dispersive Michelson interferometer comprising a cube beam splitter and a plate made of BK7 optical glass. From the retrieved spectral phase, the effective thickness of the BK7 optical glass is determined precisely. Web of Science 285 24 4738 4733

Subsurface damages induced by grinding strongly influence the mechanical strength and optical quality of optical glasses. It is meaningful to rapid evaluate the depth of subsurface cracking through the measurement of surface roughness under different grinding parameters. Based on the features of surface and subsurface cracks as well as the kinetic analysis of surface grinding, the relationship between surface roughness and subsurface crack depth was established. Surface grinding experiments for optical glass BK7 were conducted. Utilizing optical microscope, optical profiling system and polishing-etching technique, the dependence of surface roughness and subsurface crack depth on grinding parameters was systematically analyzed. The predicted model of the relationship between surface roughness and subsurface crack depth was compared with experimental results. It was found that the relationship between surface roughness and subsurface crack depth is influenced by the half apex angle of abrasive grain as well as the magnitude of extra grain extrusion.

We studied influence of platinum, antimony and iron ions on the coloration of alkali-borosilicate glass. The optical transmittances of glass specimens with and without antimony were compared, and the cause of absorption in antimony-free glass was studied. It was found in antimony-free glass that a small amount of dissolved Pt 2+ on the ppm order causes strong absorption at approximately 360 nm resulting in a yellowish color. This absorption was not observed in the specimens melted at temperatures below 1150 °C, or in the colorless specimens containing antimony or iron. It was indicated, in the colorless specimens that platinum exist as Pt 4+ , the absorption of which occurs in the UV region. The oxidation state of platinum ions was strongly affected by melting temperature or coexisting multivalent ions such as antimony or iron ions, which act as an oxidant of platinum ions. Keeping the melting temperature low and employing appropriate oxidant ions are effective means of designing colorless antimony-free optical glass.

This study presents a novel and economical method for precisely developing an extremely thin diamond grinding wheel-tool and using the finished tool to fabricate crisscross microgrooves on optical glass in situ. The wheel-blank is made of diamond grain of 0–2 μm via a developed micro co-deposition process. Micro w-EDM is employed for truing and dressing to thin the wheel-tool, which is mounted on a high-speed spindle. The finished grinding wheel is not unloaded; it is directly utilized to grind the micro crisscross grooves on optical glass. The experimental results show that desirable geometric and dimensional accuracy, as well as microgroove surface roughness can be achieved. In addition, the paper considers life expectancy for the designed wheel-tool and grinding-edge designs for cutting different shaped grooves.

A five-axis electrorheological fluid-assisted polishing equipment is presented for the finishing of curved surfaces in this paper. An integrated electrode tool is specially designed to make the abrasive particles in the electrorheological fluid concentrate around the tool end when the electric field is applied and it is suitable to polish not only the conductive material such as tungsten carbide but also the non-conductive material such as optical glass. The polishing experiments for curved surfaces of tungsten carbide and optical glass are conducted to confirm the validity and suitability of the developed five-axis equipment with the designed integrated electrode tool and to reveal the influence of the process parameters on the workpiece surface roughness in electrorheological fluid-assisted polishing.

In this work the wear behavior of cerium oxide abrasive grains during the glass polishing was studied. Polishing tests have been done by different types of cerium oxide abrasive grains. The grains have been recovered and examined during the operation. The morphology, the granulometric distribution, the chemical composition and the agglomeration phenomenon of recovered grains have been studied. The results showed that the fracture is the main cause of the abrasive grain wear of the cerium oxide abrasive grains, which permitted to the abrasive grains to preserve their initial morphology for a long time during the process. The cerium oxide abrasive grains undergo a partial wear during their use in polishing and it is closely related to the process parameters. The granular agglomeration phenomenon of the abrasive powder is very much present in the polishing process and generates bigger grains being able to influence the product quality.

Experiments were conducted to reveal the polishing properties of the Fe3O4 electrorheological fluid, which was used to form a dynamical, instantaneous tiny grinding wheel to polish optical glass. The profile of the polished area of the glass surface indicates that the material removal process is dominated by the synergy of the applied pressure and the relative velocity between the abrasives and the workpiece to be polished. It is also found that the rate of material removal is proportional to the intensity of external electric field and decreases with the extension of the machining gap between the workpiece and the needle-like tool.

The effects of linear birefringence (LB) upon bulk glass optical current transformers (BGOCTs) with different optical path designs, such as the orthoconjugate reflection (OCR)-typed, the direct reflection (DR)-typed and the roof-prism reflection (RPR)-typed BGOCT designs, are theoretically analyzed and compared with that of the BGOCT with a single-loop optical path in this paper. The results show that the return-back dual-loop current sensing designs with conventional signal processing scheme of “−/+” cannot eliminate the harmful effects of the LB thoroughly, if suitable signal processing schemes, which can separate the LB from Faraday effect, are not used.

ELID grinding is drawing more and more attention by the researchers for its smart method of in-process dressing of the grinding wheel. A number of studies have been done by many people to investigate the mechanism and application of the process, though no significant effort has been made so far to develop an intelligent machinetool especially dedicated for ELID grinding. This paper aims to present the development and performance evaluation of an ultra precision intelligent ELID grinding machine. The machine is a five-axis machine, which includes three conventional linear axes (X, Y and Z) and a spindle axis. On top, another rotational axis has been included to assist the aspheric/spherical lens grinding. In order to introduce intelligence to the machine two on machine measuring system have been developed and incorporated. Experiments have been carried out on BK7 optical glass for evaluating the performance of the machine. A nano-level surface finish has been achieved, using #4000 series wheel.

We present a detail investigation on the development of a series of gradient index (GRIN) optical glass microlens and polymer microlens and microlens arrays in our laboratory in recent years. The special glass material GRIN lenses have been fabricated mainly by using ion-exchange technology, which are applied to construct micro-optic devices and other applications. On one hand, we demonstrated the light propagation and imaging properties of GRIN lenses and the results analyzed. On the other hand, we have explored a drop-on-demand ink-jet printing method to produce microlens array using nano-scale polymer droplets involved with a uniform ultraviolet light and heat solidifying process. The experimental setup for manufacturing polymer microlens array and the performance of refractive microlens elements are also given in this paper.

This paper investigated the characteristics and the wear modes of the diamond grits in the cut-off grinding BK7 glass using thin diamond wheel. The grinding forces, the grinding ratio, the width of cut, the straightness of cut and chipping produced during the cut-off grinding were also studied. Experimental results showed that the major wear process of the diamond particles observed for a lower transverse velocity during the cutting-off BK7 glass was from protrusive, partial breakage, pulled-out, to new conditions, which obtain a freer cutting ability, a better grinding ratio and a better straightness of cut. However, when a too high transverse velocity was used, the diamond wear pattern displayed some macro-breakage and flatten conditions occurred on the worn wheel surface, thereby causing the unstable grinding forces, a low grinding ratio and a poor straightness of cut. Besides, the chipping condition of the bottom on the edge of the kerf during the cut-off grinding of BK7 glass was larger than that of the top, which is due to the down-mode grinding.

For the purpose of quantitatively evaluating laser-induced damage in optical glass, image processing was employed. The image processing involves an improved watershed segmentation algorithm, with the aid of which different morphologies of laser damage in glass were classified. The shapes and distribution of cracks can be readily discerned in the gradient image while the severity of damage is apparent in the gray-scale image after being filtered; in addition, the marker image can be utilized to recognize the region where the damage appears; the final segmentation embodies all characteristics of damaged area and is an effective means of analyzing the laser damage in optical glass.

Results of direct UV-laser writing and of self-writing in glasses are surveyed comprehensively in terms of structure and evolution dynamics of the induced waveguides, absorption and geometry of the samples, and laser parameters applied in the experiments. In addition, the underlying mechanisms of photosensitivity that give rise to the observed refractive index changes are discussed.

Theoretical and experimental evidence of light driven structuring of the matter are presented. We show that, strong light gathers electrons in glass into macroscopic bunches which manifest themselves in bubble glass surface remained after ablation.

We report frequency modulation spectroscopy measurements performed on erbium doped fluoride glasses: PZG (39% PbF 2 , 19% ZnF 2 , 42% GaF 3 ) and ZBAC (57% ZrF 4 , 34% BaF 2 , 5% CeF 3 , 4% AlF 3 ). For the ZBAC glass, no changes of lifetime in channel waveguides versus bulk were observed as well as no pump power dependence from 1 to 100 mW. On the contrary, for the PZG glass, the lifetime of the 4 I 13/2 level was reduced from 7 ms in bulk to 2 ms into the waveguides. In this glass, upconversion effects appear very efficient at high incident pump power.

Here, we bring out an infrared transmitting new optical glass based on TeO2 added with AlF3 and LiF, containing dual rare earth ions (Eu3+,Nd3+) as the dopants with a purpose to examine their luminescence and also the decay times pertaining to a prominent transition of Eu3+ (5D0 → 7F2 at 615 nm) as a function of temperature both in the presence and absence of Nd3+ ions. The energy transfer rates (Wtr), critical distances (R0) and transfer efficiencies (ηtr) have been evaluated based on the measured lifetime data of this glass.

An experimental study was carried out to investigate the mixing process of a two-layer stratified fluid in a laterally heated enclosure. Due to the lateral heating of the enclosure, a circulating flow is induced in each layer such that the interface separating the layers is simultaneously exposed to destabilizing shear and double diffusive convection. The main goal of this work is to investigate the role of the interfacial instabilities in the mixing process of the two-layer system. The experiments were carried out in a box with inner dimensions of 10×10×10 cm. Two sidewalls of the box were made of stainless steel and served as heat exchangers, and the two other sidewalls were made of optical glass to facilitate flow visualization. The criterion for the onset of interfacial instabilities and the mixing time of the system were studied experimentally. The results show that when the flow adjacent to the interface is unstable, it is characterized by intense vortices and the mixing time is relatively short. On the other hand, when the interfacial flow is stable, no vortices exist at the interface and the mixing time is much longer.

This short paper reports both the photoluminescence and the lifetime measurements of a prominent emission transition ( 5 D 0 → 7 F 2 ) of Eu3+ both in the presence and absence of the codopant rare earth ion (Dy3+) in an optical glass of the composition (79−x)TeO2+6AlF3+15LiF+xLn2O3 as a function of temperature down to 10 K.

With the goal of creating various optical glass devices for the telecommunications industry, the effects of 810 nm, femtosecond laser radiation on various glasses were investigated. By focusing the laser beam via a microscope objective, transparent but visible, round-elliptical damage lines were successfully written inside high silica, borate, soda-lime-silicate, fluoride and chalcogenide glasses. Microscopic ellipsometric measurements of the damaged region in pure and Ge-doped silica glasses showed refractive index increases of 0.01 to 0.035. The formation of several types of defects, including Si E′ or Ge E′ centers, non-bridging oxygen hole centers, and peroxy radicals, was also detected in addition to the identification. These results suggest that multi-photon interactions occurs in the glasses and that it is possible to write three-dimensional optical circuits in bulk glasses via such a focused laser beam technique.

A technique for obtaining liquid–liquid–vapour equilibria data in a single apparatus is described. The cell, equipped with two facing optical glass windows and a turbidimeter, is stirred at two regimes. At high agitation speed, the hollow shaft induces the vapour-phase recirculation in the liquid and allows very quick liquid vapour equilibria measurements, with a saw tooth temperature profile at each composition. At moderate agitation speeds, the liquid cloud point is detected by turbidimetry. The technique leads, in a matter of few days, to a complete set of data in a large P and T domain. As an example, an application to the MIBK-water binary system is presented.

In view of the increasing filler content, processing temperatures and throughput in plastics, wear in processing will remain a problem. This is particularly true of processes where no surface damage is permitted because of the subsequent change of dimensions or the intoxicating effects of the loosened particles, as is the case, for instance, in the manufacture of polymeric optical glass fibres. In particular, raw materials that exhibit abrasiveness as well as corrosiveness create a severe complex tribological load. The surface of processing equipment must be hard enough to withstand the mechanical attack of the hard glass fibres and should also be corrosion resistant. The potential of PVD coatings for wear protection in plastic processing has been studied when exposed to solid as well as molten plastic raw material. Wear tests have been carried out for commercially available glass fibre-reinforced polyamide (PA) and glass fibre-reinforced polyphenylene sulphide (PPS). The methods used were the platelet apparatus for the molten materials and the DKI universal wear and friction tester for the solid raw material. It was found that PPS (compared with PA) created higher abrasion in the solid zone and lower abrasion in the plasticized stage, although it may have higher corrosiveness. Among the PVD coatings tested the best results were achieved with CrN. In comparison with standard metals used for plastics machining the results show that, in general, PVD coatings offer a good opportunity for wear protection: not so much in the solids conveying zone but more so in the melt zone. As yet little is known about the scope of multi-layered PVD coatings, in which by combining the individual layers a combined wear resistance against complex loads may be achieved.

A new type of oxygen sensor is proposed with an ion-sensitive film of V 2 O 5 on an optical waveguide surface and is characterized using prism-film coupling. Upon exposure to excess oxygen in ambient air, the light ( λ =632.8 nm) transmission through the guide alters due to the change in the refractive index of the film, changing the effective index of the guide. The excess O 2 concentration varies from 50 ppm to few per cent (5%). The influence of the cladding thickness (150–490 nm) and the length (2–6 mm) on the sensor performance are studied. The increase in cladding length enhances the static sensitivity, while the increase in the thickness causes a reduction in the static sensitivity, unaffecting the incremental sensitivity. The performance is identical with static and incremental methods. The response and recovery times are found to be 4–6 and 8 s, respectively. An air ambient sintering of the films gives practically a linear response compared to nonsintered films. The sensors are tested for other gases, namely H 2 and H 2 O, does not show any response except O 2 .

The variation of the concentration-dependent diffusion process with ion exchange temperature from 280 degrees C to 400 degrees C has been investigated in two-boro-aluminosilicate glasses suitable for micro-optic applications. Silver dopant concentration profiles are measured using energy dispersive X-ray spectroscopy and converted to concentration dependence using an analytical formulation of the Boltzmann Matano analysis. Extensive error analysis of the Boltzmann-Matano method is presented. While the overall interdiffusion rates vary strongly with temperature, the temperature variation of the concentration dependence does not exceed experimental error. Temperature dependencies of Ag and Na self-diffusion coefficients are also presented. The activation energies for Ag and Na are both approximately 0.72 eV in these glasses.

The importance of ductile regime cutting has been emphasized in the production of large-diameter optics and semiconductor substrates over the last ten years. However the available technology has not yet been implemented in industry. The reason is that cutting technology based on the motion-copying principle is too sensitive for error motions of a machine tool to maintain the actual depth of cut stably below the critical depth. A new cutting technology using a flying tool under negative pressure has been developed. In this technology, a flying tool glides over a workpiece surface while maintaining a small height like a negative-pressure slider of a magnetic disc drive. Using the tool system, ductile regime cutting of optical glass and monocrystalline silicon was examined, and a mirror-surface finish with no cracks was achieved on a face lathe having a 0.1μm order of error motion.

The accuracy, sensitivity and main sources of systematic errors of reflectometric techniques applied to optical glass refractometry are analyzed. The results show how real performances of the light source, collimators and polarizers limit the accuracy of reflectometry as refractometric technique. The observation geometrics that have been considered are: normal incidence, Brewster angle and 45° incidence.

The study is aimed at the evaluation of the relationship between the measured (or imposed) constant curvature of the coating of an optical glass fiber and the elastic curve of the fiber itself. It is shown that the buffering effect of the coating is different for different points along the curved area and depends on the length of this area, and the compliance of the coating. In the case of a very short curved area and/or a very compliant coating, the curvature of the glass fiber is smaller than the curvature of the coating and increases with an increase in the length of the curved area and the coating stiffness. In the case of a long curved area and/or a stiff coating, both curvatures are practically the same for almost the entire curved area. Only when approaching the ends of this area, the ratio of the curvature of the glass fiber to the coating curvature somewhat increases (by a factor of 1.043) and then rapidly drops to unity at the ends. There are, however, some “intermediate” unfavorable combinations of the lengths of the curved area and coating compliances that result in curvature ratios exceeding (by up to a factor of 1.086) the coating curvature in the midportion of the curved area. It is shown that such a paradoxical situation is due to the redistribution of the interfacial radial load at certain combinations of the lengths of the curved areas and spring constant of the coating. For a current AT&T dual-coated fiber design with a 30 μm thick silicone primary coating, the curvature ratio is greater than unity when the lengths of the curved area fall within the range between 1.84 and 4.27 mm, and reaches the 1.086 value when the length of curved area is about 2.44 mm.

This paper presents the preparation and photoluminescence characteristics of a new series of Nd 3+ -doped InF 3 based glass systems of the following compositions: 48 InF 3 24 BaF 2 7 AlF 3 20 RF1 NdF 3 where RF=LIF, NaF and KF. Besides our understanding of the optical properties, the relevant physical properties concerning these glasses have also been dealt with. Based on the fluorescence results obtained from both the theory and experiments on these optical glasses, it was found that the Nd 3+ -doped Glass-A with 20 M% LiF was better in optical behaviour than the other two glasses.

A 30 layer copper tetra-4-(2,4-di-t-amylphenoxy)phthalocyanine(tapCuPc) film was deposited onto an optical glass waveguide of K ion-exchanges by the Langmuir-Blodgett (LB) technique. A four-layer dielectric waveguide with a LB film cladding was formed. Optical bistability of the optical waveguide coated with nonlinear tapCuPc LB film was observed at room temperature for the first time.