Glass Refractive Index Research Articles

New Er3+-doped gadolinium borogermanate glasses for optical telecommunication

New Er3+-doped gadolinium borogermanate glasses were synthesized to investigate their physical, structural, optical, and luminescence properties in this work. The influence of Er2O3 concentration on those properties were studied to determine the optimum glass composition for photonics material. Glass density, molar volume, refractive index, polarizability, and field strength increase, while Er3+ inter-ionic distance decreases via adding Er2O3 concentration. From XRD and FTIR results, the tetrahedral BO4 and trigonal BO3 borates are the main structural units those connect in amorphous nature to form as a glass network. Glasses absorb the photons in ultraviolet, visible light and near-infrared region under Er3+ transitions. Glasses generate the strong infrared emission around 1.5 μm under the 4I13/2 → 4I15/2 transition of Er3+ ion. The 3.0 mol%-Er2O3 doped glass performs the highest emission intensity due to the concentration quenching effect. The luminescence decay time is shortened from ∼0.8 to ∼0.4 ms by adding Er2O3 content. Judd-Ofelt and MacCumber analysis indicate high potential of glass for using as an optical amplifier in telecommunication applications, due to its large luminescence bandwidth.

Novel Tb3+ doped borophosphate glass scintillator for X-ray imaging

In this study, we introduce an efficient green-emitting material made from Tb3+ doped borophosphate scintillating glass for X-ray imaging. An influence of Tb2O3 concentration on the physical, optical, luminescent, and scintillation properties of glasses were investigated. The glass density and refractive index increase, while the molar volume and Tb3+ inter-ionic distance decreases with Tb2O3 addition. These glasses absorb the photons in range of UV, Vis, and NIR. The excitations by UV and X-ray on glasses causes the strong green emission centered around 545 nm by the 5D4 → 7F5 transition of Tb3+. The energy transfer from Gd3+ to Tb3+ was occurred in this emission. The glass doped with 4 mol% of Tb2O3 demonstrates the highest emission intensity at 545 nm due to the concentration quenching. The decay time of glasses are in few milliseconds. The integral X-ray scintillation efficiency of 4 mol% doped glass is 52% compared to that of BGO crystal. Additionally, this glass was proceeded in the X-ray imaging and yielded the image with satisfied resolution, characteristics and MTF values, compared to that obtained from YAG:Ce crystal. The developed glass has a potential for X-ray imaging applications, especially in the medical imaging, flaw detection, and security inspection.

Glass bonding of YAG/Nd:YAG and Sapphire/Nd:YAG windows

Transparent ceramic assemblies are of great interest and challenge for many optical applications. Lead silicate-based glass was successfully utilized to bond YAG/Nd:YAG and sapphire/Nd:YAG substrates at 850 °C in air. The glass's thermal characteristics and refractive index were measured and found to be comparable to those of YAG and sapphire. Microstructure and composition analysis of the glass bonding interface reveals no evidence of flaws or reaction products. The in-line transmission results of the YAG/Nd:YAG and sapphire/Nd:YAG assemblies are equivalent to those of the initial Nd:YAG ceramics throughout a wide wavelength range (450–1200 nm). The reported findings establish an efficient approach for future design and implementation of complex optical systems with enhanced optical and thermal properties.

TB3+ CONCENTRATION EFFECT ON THE PHOTO - AND RADIOLUMINESCENCE RESULT OF LANTHANUM BORATE GLASS FOR YELLOWISH GREEN LASER APPLICATION

The melt-quenching technique was used to prepare lanthanum borate glass doping with Tb3+ (LBTb) to investigate physical and luminescent characteristics. The result more a concentration of doped terbium increases the glass density, molar volume, and refractive index. The higher Tb2O3 concentrations in glasses led to an increase of absorbance in the VIS and NIR range. The emission spectra of glasses were recorded at excitation wavelengths of 228 and 377 nm, and it was found that these glasses emit yellowish-green light. Tb3+ doped glass exhibited the highest intensity at 544 nm. The optimal concentration of terbium with the most significant emission in LBTb glass is 7 mol%, whereas decay time decreases as Tb2O3 content increases. The PL measurement showed a similar pattern with the spectrum of RL emissions. Moreover, this glass performs an integral scintillation efficiency of 36.32% compared with BGO crystal. According to the CIE 1931 chromaticity, the LBTb emitted a yellowish-green color. Terbium-doped glasses have attractive potential to be used in yellowish-green lasers.

Structural and spectroscopic correlation in barium-boro-tellurite glass hosts: effects of Dy2O3 doping

In this study, a series of barium-boro-tellurite glass hosts with varying concentration of Dy2O3 doping (0 to 1.25 mol%) were made by melt-quenching method. A study was conducted to investigate how Dy2O3 dopants affect the physical and spectroscopic traits of glasses. Raw materials including barium oxide (BaO), tellurium dioxide (TeO2), boron oxide (B2O3), and dysprosium oxide (Dy2O3) were used to produce these glasses. XRD patterns of the samples showed a broad hump and absence of long-range periodic lattice arrangements, indicating their amorphous nature. The Raman spectral analyses displayed the various vibration modes where the most intense band caused by BaO vibrations at 300 cm-1 and 450 cm-1 corresponding to the symmetric stretching vibration mode of Te–O–Te intra-chain bridges. The peak at 750 cm-1 was due to TeO4 and Te-O-Te vibration modes. The value of optical band gap energy was decreased from 3.155 to 2.1894 eV and then increase at higher Dy2O3 level (0.75 to 1.25 mol%). At Dy3+ contents between 0.25 to 1.25 mol% seven absorption bands were observed at 390, 424, 452, 750, 797, 895 and 1092 nm due to the electronic transitions in Dy3+. The glass refractive indices were raised from 2.3563 to 2.6584 and then decreased at higher Dy2O3 contents which was mainly because of the generation of more bridging oxygen (BO) in the glass matrix. The value of glass electronic polarizability and oxide ions polarizability calculated using LorentzLorenz equation showed a decrease with the rise of Dy2O3 contents, which was ascribed to the presence of fewer non-bridging oxygen (NBO). The optical basicity of the proposed glass hosts was calculated using Duffy and Ingram equation which was decreased with the increase of doping contents. In addition, the optical transmission was increased and reflection loss was reduced with increasing Dy+3 levels. The value of metallization parameter below 1 proved the true amorphous nature of the prepared samples. All the glasses revealed blue and yellow photoluminescence emission peaks due to 4F9/2→ 6H15/2, and 4F9/2 →6H13/2 transitions in Dy3+, respectively. The proposed glass compositions may be beneficial for the advancement of solid-state lasers.

Creating an Array of Parallel Vortical Optical Needles

We propose a method for creating parallel Bessel-like vortical optical needles with an arbitrary axial intensity distribution via the superposition of different cone-angle Bessel vortices. We analyzed the interplay between the separation of individual optical vortical needles and their respective lengths and introduce a super-Gaussian function as their axial profile. We also analyzed the physical limitations to observe well-separated optical needles, as they are influenced by the mutual interference of the individual beams. To verify our theoretical and numerical results, we generated controllable spatial arrays of individual Bessel beams with various numbers and spatial separations by altering the spectrum of the incoming laser beam via the spatial light modulator. We demonstrate experimentally how to implement such beams using a diffractive mask. The presented method facilitates the creation of diverse spatial intensity distributions in three dimensions, potentially finding applications in specific microfabrication tasks or other contexts. These beams may have benefits in laser material processing applications such as nanochannel machining, glass via production, modification of glass refractive indices, and glass dicing.

Micro-patterned glass for energy-efficient windows

Development of novel energy-efficient components is a topic of prime importance in building design. In this contribution, we propose a micro-patterned glass window which can be designed to efficiently reduce the energy demands of buildings located within an area of hot and cold seasons. The proposed patterned structure can be applied to any panes of glass in single or multi-pane windows. We first define the total positive power as a characteristic parameter for evaluating the effectiveness of using the designed window in reducing the average thermal power demands of a given building. Then, a full-wave numerical method is employed to analyze the performance of the proposed structure with respect to the defined characteristics. Our model accurately accounts for sunlight incident angle variations corresponding to different times of the days in every season. In addition, the variations of glass refractive index throughout the solar spectrum, non-polarized nature of the sun light, and typical dimension scales used in building windows are taken into account. Our numerical results show more than 80 W and 160 W total positive power for an optimized single-pane micro-patterned window with unit area and a double-pane one, respectively. We also present the design procedure of the proposed structure for a given geographical location of the building.

Femtosecond laser-induced glass refractive index change in tellurite glass

Tellurite glass has excellent infrared optical properties and is widely used in lasers, optical communications, and sensing. Femtosecond laser direct writing is a preferred method for manufacturing tellurite photonic devices, which requires precise control of the variable of refractive index. However, accurate testing of the refractive index changes induced by femtosecond laser in tellurite glass is challenging due to the small magnitude of change and localized region. In this study, we present a novel approach to measure the refractive index change of tellurite glass through the utilization of volume phase grating (VPG) diffraction. We first investigated the laser-induced damage threshold (LIDT) of tellurite glass and then proceeded to prepare VPGs inside the glass by using femtosecond laser direct writing technology, ensuring that the laser energy remained below the LIDT. By measuring the thickness and diffraction efficiency of VPGs prepared under different laser energies, we determined the associated change in refractive index. In our experiment, when subjected to laser incidence with wavelengths of 632.8 and 808 nm, the maximum values of refractive index change in the laser-modified region are measured to be 1.97 × 10−3 and 1.61 × 10−3, respectively. This method offers a precise means of measuring refractive index change within the microregion of tellurite glass induced by femtosecond laser. This capability holds great significance for the fabrication of high-quality tellurite glass photonic devices using lithography-based techniques.

Preparation of gradient refractive index films on glass surface and its anti-reflection properties

This study presents the creation of a gradient refractive index film on the surface of aluminosilicate glass using a two-step process involving chemical etching and subsequent multilayer sol-gel coating with hollow silica nanospheres. The primary objective was to achieve effective anti-reflection properties. Various analytical techniques such as FESEM, TEM, UV-Vis-NIR spectrophotometry, ellipsometer, and FT-IR spectrometry were employed to investigate the impact of glass surface morphology and refractive index on optical characteristics. The results revealed the successful formation of a porous structure on the glass surface through chemical etching. Subsequently, this porous structure was uniformly filled and layered with hollow silica spheres of different sizes, resulting in a stepwise gradient refractive index coating. Notably, the pore size of the hollow spherical silica colloidal particles progressively increased from 0 nm to 23 nm, corresponding to distinct film thicknesses and refractive indices. This stepwise modulation contributed to the establishment of a gradient refractive index within the coating. By transitioning the refractive index of the film layer from that of glass to air, the film acted as a matching layer, thereby achieving broadband anti-reflection. The efficiency of this anti-reflection was demonstrated by an increase in transmittance from an initial value of 91.8–95.32% following the two-step etching process. With the subsequent SiO2 coating, the transmittance continued to improve, ultimately reaching a high value of 97.47%. This improvement in transmittance was attributed to the gradual enhancement of the film layer.

Impact of non-bridging oxygens on the thermal, electrical and optical properties of germanate glasses and exploration of the germanate anomaly

In this study, we successfully prepared quaternary germanate glasses (Bax/3Srx/3Cax/3)Ge(1-x)O3 (x = 0.1–0.5) using a containerless solidification method. The structure of the germanate amorphous materials was characterized using techniques such as XRD, SEM, TEM and Raman. We evaluated the thermodynamic properties of the amorphous materials using differential scanning calorimetry and investigated their crystallization activation energies. In terms of application performance, we measured electrical conductivity and impedance spectra for the electrical properties, while the optical properties were assessed through the refractive index and transmittance. The results revealed that the (Ba0.2/3Sr0.2/3Ca0.2/3)Ge0.8O3 system represented the germanium anomaly point. Due to the highest number of ternary rings and the most compact structure within this system, the values of density, glass transition temperature, refractive index, and bandgap all reached their maximum. As the content of alkaline earth oxides increased, the glass network structure gradually fractured, leading to an increase in non-bridging oxygens and corresponding changes in properties.

Influence of CeF3 on Ga2O3-Lu2O3-Al2O3-Y2O3-B2O3 glass for photonics material

CeF3 doped gallium lutetium aluminium yttrium borate glasses were investigated for photonics applications in this work. Their physical, structural, optical and luminescence properties were studied by the effect of CeF3 concentration. Glass density and refractive index raised with increasing CeF3 amount. The FTIR spectra and XRD pattern demonstrated that the glass network consisted of trigonal BO3 and tetragonal BO4 borate groups cooperating with metal oxides in amorphous nature, while CeF3 dopant acted as a glass modifier. Glass strongly absorbed the photons in ultraviolet region by transition of host component, superposed with the 4 f→5d transition of Ce3+ dopant. Under UV excitation, glass doped with 0.05 mol%-CeF3 performed the highest emission intensity at 391 nm by 5d→4 f transition. Due to the strong blue emission, half photons conversion ability and short decay time around 21 ns, this developed glass owns a potential for the blue light sources / medium and the ultraviolet to visible light converter.

Fully Bio-Based and Solvent-Free Polyester Polyol for Two-Component Polyurethane Coatings

In recent years, many efforts are being devoted to the development of new materials that originate from renewable resources. Polyesters are one of the most important classes of such materials and several bio-based monomers are available for their synthesis. In this work, the development of fully bio-based and solvent-free polyester polyol used for two-component polyurethane coatings on industrial scale is presented. Fossil-based raw materials were substituted with bio-based alternatives that are commercially available on a large scale. Properties of polyols and coatings were determined and measured. Polyols were characterized by the determination of acid number, hydroxyl number, glass transition temperature and refractive index, and measurement of viscosity, color and molecular weight. Coatings were characterized by the determination of mechanical properties, such as hardness, elasticity and impact resistance, and the measurement of optical properties such as gloss, haze, distinctness of image (DOI) and reflected image quality (RIQ) and weathering resistance. Three variations of bio-based polyol were synthesized, then the most suitable version was validated in a clear coat. The results showed that the properties of the bio-based polyol and coating met the requirements and were comparable to the properties of the synthetic counterpart. Results indicate that this newly developed 100% bio-based and solvent-free polyol can be used as a drop-in replacement for synthetic polyol. Furthermore, this work implies that the supply chain is established which allows the green transition in the paint industry.

Thermal performance of a novel double-glazed window combining PCM and solar control glass in summer

The integration of PCM into glazed envelope to enhance its thermal inertia has shown great energy-saving potential. However, this could bring indoor overheating in summer due to the insufficient heat insulation for solar radiation in pure PCM glazed units. This work proposed a composite double-glazed window incorporating PCM and solar control glass, and numerically investigated its thermal behaviors under sunny and cloudy conditions in summer of northern China. The effects of glass optical properties, involving absorption coefficient and refractive index, on the phase change cycling, indoor thermal comfort and building energy efficiency were analyzed. The results show that the increase of glass absorption coefficient facilitates the melting of PCM, but degrades the thermal comfort, even resulting in overheating risk on the sunny day. Moreover, as the absorption coefficient and refractive index of glass increase, the energy efficiency of PCM window equipped with solar control glass instead of general glass can be improved remarkably, and the influence of refractive index is more drastic than that of absorption coefficient. On the sunny day, the energy saving rate is 14.25% for the glass absorption coefficient of 160 m−1, which is 41.53% for the glass refractive index of 3.

Alternating Copolymerization of Epoxides and Isothiocyanates to Diverse Functional Polythioimidocarbonates and Related Block Polymers†

Comprehensive SummarySynthesis of diverse polythioimidocarbonates via ring‐opening copolymerization of epoxides and isothiocyanates catalyzed by organoboron catalyst was reported herein. Both aromatic and aliphatic isothiocyanates underwent successful copolymerization with terminal and internal epoxides, allowing for the precise tuning of the performance of the resultant copolymers over a broad range. The wide scope of available isothiocyanates and epoxides enables the direct construction of sulfur‐containing functional polymers featuring both high glass transition temperature and refractive index. Additionally, it was observed that aromatic isothiocyanates polymerize much faster than aliphatic ones, and the reactivity difference facilitated the one‐step synthesis of block polymers from mixed aromatic isothiocyanates, aliphatic isothiocyanates and epoxides due to the preferential incorporation of aromatic isothiocyanates over the aliphatic analogues during their alternating copolymerization with epoxides. The produced polythioimidocarbonates can be used as positive resists for electron beam lithography (sensitivity of 130 μC/cm2 and contrast of 1.53 for poly(CHO‐alt‐EITC)). Coupling with their high refractive index (1.58—1.68), polythioimidocarbonates might find functional applications in optics. These results render ring‐opening copolymerization of epoxides and isothiocyanates a facile route to enrich functional polymer library.

Analysis of the Transmission Spectrum of Flat Glass from Near-infrared to the Ultraviolet

Contemporarily, glass windows have a great impact on human beings’ daily life. It is crucial to design a glass with a reasonable thickness with a high transmission of visible light as well as a high reflection of near infrared light. In general, reflection from the glass surface and absorption of light waves by the glass material are important features for transmission. Therefore, for UV-visible near-infrared light waves, the greater the thickness of the glass, the greater the light absorption loss and the lower the transmission rate. However, it is believed that there are multiple reflections of light waves in flat glass and that the losses caused by reflections should also be related to the refractive index of the glass and the wavelength of the incident light. On this basis, this study has developed theoretical models of transmittance versus incident light wavelength and glass thickness, refractive index and absorption coefficient. According to the theoretical analysis, the thickness of the glass has a significant effect on the transmission spectrum of sunlight. To experimentally verify this theoretically predicted anomaly, this paper designed the experimental and measurement route and built the experimental test rig. A variety of glass samples in the thickness range of 1mm-10mm were designed and prepared for this project, and the UV-Vis-NIR transmission of the glass was scanned and measured, while the final measurement results observed anomalies in the variation of transmission with thickness. The experimental results, therefore, provide valid support for the theoretical model of this paper.

Accelerated design of chalcogenide glasses through interpretable machine learning for composition–property relationships

Chalcogenide glasses (ChGs) possess various outstanding properties enabling essential applications, such as optical discs, infrared cameras, and thermal imaging systems. Despite their ubiquitous usage, these materials’ composition–property relationships remain poorly understood, impeding the pace of their discovery. Here, we use a large experimental dataset comprising ∼24 000 glass compositions made of 51 distinct elements from the periodic table to develop machine learning (ML) models for predicting 12 properties, namely, annealing point, bulk modulus, density, Vickers hardness, Littleton point, Young’s modulus, shear modulus, softening point, thermal expansion coefficient, glass transition temperature, liquidus temperature, and refractive index. These models are the largest regarding the compositional space and the number of properties covered for ChGs. Further, we use Shapley additive explanations, a game theory-based algorithm, to explain the properties’ compositional control by quantifying each element’s role toward model predictions. This work provides a powerful tool for interpreting the model’s prediction and designing new ChG compositions with targeted properties. Finally, using the trained ML models, we develop several glass-selection charts that can potentially aid in the rational design of novel ChGs for various applications.

Accurate compensation and prediction of the temperature cross-sensitivity of tilted FBG cladding mode resonances.

The temperature dependence of core mode resonance has been thoroughly studied in fiber Bragg gratings (FBGs), but it is not the case for cladding mode resonances in multi-resonance gratings such as tilted FBGs (TFBGs). In this work, the temperature sensitivity of ultraviolet written TFBGs in SMF-28 fibers is assessed, demonstrating in the first, to the best of our knowledge, place that a single gauge factor K T=6.25⋅10-6±0.02⋅10-6 ∘ C -1 can be employed to characterize the response to temperature of the resonances over the full spectrum in the 10°-50°C range. Then, a simulation model is obtained, enabling to predict TFBG spectra in the 10°-50°C range with high accuracy. This requires a calibration of the core index and dispersion of the TFBG measured in air at 25°C, and determination of the glass refractive index thermo-optic coefficient (d n/d T=8.46⋅10-6±0.1⋅10-6 ∘ C -1, common to both core and cladding glasses), leading to a mean error on the wavelength position of resonances between 1 and 3pm. This mean error can be further reduced (less than 1pm) by considering a linear dependence with temperature of d n/d T. Therefore, this model will enable to completely remove the temperature-induced shifts of all resonances in TFBG sensing applications and measure with great accuracy the variables of interest by using the scaled averages of groups of resonances instead of (less accurate) individual shifts.

Luminescence Properties of Samarium Ion‐Doped Silicoborate Glasses for Application in Optoelectronic Material

Gadolinium sodium silicoborate glasses doped with samarium ion (Sm:GNSB) are prepared by the melt quenching technique. The glasses are studied for their physical, optical, and luminescence properties. The density, molar volume, and refractive index of glass are investigated as a function of Sm2O3 concentrations. Addition of Sm3+ ions in the glass matrix shows several absorption peaks in the visible and near‐infrared region, verified by the absorption spectra. The energy transfer from Gd3+ to Sm3+ is observed by photoluminescence (PL) emission spectra, which illustrates the strongest emission occurring at 600 nm (4G5/2 → 6H7/2). The PL decay time of 600 nm emission under 403 nm excitation decreases with increasing Sm2O3 concentrations. The color coordinates of the International Commission on Illumination chromaticity show different shades of orange color under different excitations. The result of radioluminescence shows a similar trend to PL emission spectra. Glasses doped with Sm3+ ions find potential use as an orange color‐emitting optoelectronic device application.

Colorless SnO- and Sb2O3-containing borate and borosilicate glasses with small photoelastic and high refractive properties

We examined the relationship between optical properties and structures of 5s2-type cations such as Sn2+- and Sb3+-containing borate and borosilicate glass. Linear evolutions were observed for the compositional dependences of density, glass transition temperature, refractive index, and photoelastic constant in visible transparent oxide glasses. The structural information was provided using vibrational spectroscopy to elucidate polyhedral units of the borate and borosilicate systems. A weak ligand field around a Sn2+ close to tetrahedral borate unit, which is supported by applying density functional theory calculation, might lead to a blueshift of optical bandgap keeping small photoelastic constant and high refractive index.

Development and characteristics of infrared gradient refractive index chalcogenide glasses by hot pressing.

Compared with ordinary uniform lenses, the length and refractive index distribution of gradient refractive index (GRIN) lenses can effectively correct aberration and chromatic aberration. This advantage makes the miniaturization, integration, and lens lightweight possible. Although the visible GRIN lenses based on silicate glass are widely used, the infrared GRIN lenses based on chalcogenide glass are still elusive. This paper introduces a new method for preparing this kind of lens by hot pressing sintering diffusion of chalcogenide glasses. A series of chalcogenide glasses Ge10As22Se68-xSx (x = 4, 7, 10, 14, 24, 28, 34 mol%) with refractive index range from 2.37 to 2.57 (n@8 µm) and similar glass transition temperature (ΔTg < 10℃) were prepared by melt quenching. The relationship between Raman peaks and the refractive index of glasses was studied. Furthermore, the refractive index profile formed by elemental diffusion was characterized by Raman signals. The results show that the diffusion length reaches more than 290 µm, and larger diffusion distances can be achieved by stacking multiple layers. The obtained GRIN glass maintains good transmittance in the whole atmospheric window of 2 ∼ 12 µm.