Infrared optics technology has continued to advance in both military and civilian applications. In parallel, infrared transmitting lenses have been developed to improve the performance of infrared cameras. However, commercial Chalcogenide glass includes As or Sb which are not unsuitable for smart devices. To address this issue, novel Ge-Ga-Se ternary compositions were developed and evaluated for the lens applications. XRD was used to determine the glassforming ability. glass transition temperature was measured to determine the thermal properties. Some mechanical properties such as Knoop hardness and its coefficient of thermal expansion were performed to determine the durability of the glass. The average transmittance in the range of 8~12μm shown 60.819% and the refractive index @8, 10, 12μm were 2.51425, 2.50706 and 2.49798, respectively. The dispersion of current system shows 92.63, which is good enough to design LWIR lens.
Multispectral infrared sensor is a novel technology for detecting infrared, providing simultaneous spectral and spatial information of the target object. However, conventional multispectral infrared sensors face limitations in quantum efficiency due to a low pixel filling ratio. The integration of bandpass filters and sensors poses challenges, including processing difficulty, filter layer thickness, and material constraints.
In this work, we present a highly efficient, miniaturized optical filter with a plasmonic filter-based microlens array for a high-efficiency multispectral infrared sensor. Microlens arrays enhance light-gathering efficiency in infrared elements, resulting in high quantum efficiency, while the plasmonic filter, utilizing a 3D post array nanostructure, offers wavelength selectivity. This approach streamlines the integration of micro/nanostructures into infrared imaging sensors, significantly enhancing sensing performance beyond existing methods.
Lithium tantalate (LiTaO3) crystal is widely used in infrared detection, acoustic surface wave devices and optical applications due to its outstanding piezoelectric, pyroelectric, and nonlinear optical properties. Over the past few decades, LiTaO3 single crystals have been studied intensively for their excellent acoustic and electro-optical properties. Today, most of LiTaO3 single crystals are made by czochralski methods, which is well-defined growing methods for high quality single crystal. To grow LiTaO3 single crystal in optimized condition, hot-zone structure should be designed properly. Temperature gradient, melt flow and heat dissipation should be optimized by managing the hot-zone structure. Especially, minimizing the heat dissipation and temperature gradient play a key role deciding the quality of grown single crystal.
In this study, we designed hot-zone structure in czochralski furnace for LiTaO3 single crystal growth. We added ring parts above the iridium crucible in which LiTaO3 crystal grow. It reduced heat dissipation and temperature gradient inside the hot-zone through bothering heat flow toward upper side of the system. Vertical and horizontal temperature gradient in whole range position was analyzed. Optimized size and position of ring parts were designed. For the simulation of this system, CGSim SW was used. We expect that our research results would contribute to the development of LiTaO3 single crystal growing technology.
LiTaO3 (lithium tantalate) crystal is widely used in infrared detection, acoustic surface wave devices and optical applications due to its outstanding piezoelectric, pyroelectric, and nonlinear optical properties. Over the past few decades, LiTaO3 single crystals have been studied intensively for their excellent acoustic and electro-optical properties. For the single crystal growth of LiTaO3, raw materials of Li2CO3 and Ta2O5 need to be pretreated to form LiTaO3 polycrystal. However, high temperature, more than 1200 °C and long heating time are required for adequate crystallization.
In this study, we prepared LiTaO3 polycrystalline powder by solid state reaction synthesis from the raw powder of Li2CO3, Ta2O5, and cyanuric acid, which is an additive for a short reaction time and relatively low temperatures. The cyanuric acid, added into the mixture of Li2CO3 and Ta2O5, plays a role of fuel and inducer to produce intermediate compounds. Several temperatures and cyanuric acid composition ratio were employed to optimize the synthesis condition of pretreated LiTaO3. Structural and composition analysis were conducted to characterize the synthesized LiTaO3 powders. The optimized synthesis shows excellent ability to reduce lithium-ion volatilization and suggests an efficient way to manufacture high-quality LiTaO3 polycrystalline powders.
LiDAR (Light Detection and Ranging) is thought to be one of the necessary sensors for automatic driving systems and advanced driver assistance systems. Recently, the LiDAR of the automotive vehicle is installed in the grille or near the headlights. These installed positions are very weak for a variety of pollutions. One of the measures to keep the LiDAR window surface clean is the use of anti-fingerprint coating. In this study, the hybrid optical coating for automotive LiDAR window (BK7 glass) which have the multifunction of UV-VIS absorption, NIR transmission, mechanical hardness and easy cleanability was developed. The surface hardness of the whole front coating and performance of anti-fingerprint coating were measured. The several reliability tests were performed. The coated window passed all tests.
For chalcogenide-based infrared glass materials, the need was emphasized along with the spread of thermal imaging cameras in COVID 19 environment. Commercial Ge-As-Se glass system exhibits a dispersion value of 100~180 and a refractive index of 2.5 or more, and is suitable for the glass molding process, so it is used as an aspherical infrared lens for various thermal imaging cameras. However, some compositions are not suitable for glass molding process. In this study, the composition of the long wavelength infrared glass melting was designed based on the Ge-As-Se system with a Ge composition range of 0~35 at%, As composition range of 20~40 at%, and Se composition range of 25~60 at%. As a result of XRD analysis for each Ge-As-Se-based composition, it was confirmed that all amorphous grains were obtained in the developed composition area. For the Ge-As-Se glass-forming composition region, the glass transition temperature ranged from 180 to 425°C. The refractive index was measured using the prism method in the 3 to 12 μm wavelength band. The refractive index (λ=10 μm) of Ge5As40Se55 and Ge5As35Se60 was 2.6913 and 2.6538, respectively. Moldability test was performed using a glass molding press. As a result of observing whether the lens has internal defects and microcracks after molding, it was confirmed that there was no abnormality and that it was suitable for glass molding process.
The sealing method using a laser has been widely used since laser beams supplied locally the necessary energy to allow the formation of a hermetic bonding. The most common sealing techniques using a glass frit and a screen printer have some problems such as pores, non-uniform height, imperfect hermetic sealing. To reach high quality of laser sealing, the difference of coefficient thermal expansion (CTE) between the laser sealing glass and glass substrate should be lower than 1.0×10-6/K. In order to prove the feasibility of novel laser sealing glass as a fiber type sealant, PbO-SiO2-Al2O3-B2O3 based glass system was drawn with fiber types ranging from 180 μm to 1000 μm in diameter. CuO and Na2CO3 were added into PbO-SiO2-Al2O3-B2O3 glass system in order to tuning the CTE. The thermo mechanical and thermal properties were investigated for correlations the CuO and Na2CO3 concentrations with PbO-SiO2-Al2O3-B2O3 glass system. The 1wt% CuO and 1wt% Na2CO3 co-doped PbO-SiO2-Al2O3-B2O3 glass system shows the CTE of 9.53×10-6/K. In this study, the FTO-coated glass substrate with a CTE of 10.23×10-6/K was sealed with fiber type sealant made of the CuO and Na2CO3 co-doped PbO-SiO2-Al2O3-B2O3 glass system. These results indicate that the fiber type sealant is feasible as laser sealing material in the packaging industry.
A diamond-like carbon thin film was deposited on the outer face of the germanium (Ge) window to protect the infrared lenses from a harsh environment in automotive application. Infrared transmittance and residual stress of a tetrahedral amorphous carbon (ta-C) thin film by a filtered cathodic vacuum arc (FCVA) source were investigated to increase the lifetime of a Ge window. They were found to have a trade-off relation about the change of the substrate pulse voltage. By introducing methane gas in FCVA deposition process, a hydrogenated ta-C (ta-C:H) thin film of which both IR transmittance and residual stress was improved could be obtained. A Ge window coated with ta-C:H thin film with 1.43 μm thickness showed anti-reflective effect in long-wave infrared. The hardness of ta-C:H thin film on Ge window was higher than 30 GPa. Adhesion, severe abrasion, temperature, humidity and salt solubility tests were carried out in accordance with MIL-C-48497A.
In the present study, zinc molybdenum tellurite glasses with the molar composition of (1−x)TeO2−yMoO3−xZnO and (1−x)TeO2−yMoO3−xZnO, where x = 10, 20, and 30 mol%, and y = 10 and 20 mol%, were prepared by a high temperature melt quenching technique and studied their thermal, thermo-mechanical and mechanical properties. From the thermal analysis, it was found that the glass transition (Tg), crystallization (Tx) and stability parameters slightly increased with increase in ZnO content in both series of glasses. Thermal expansion coefficient decreases from 16.56 to 14.67×10-6/K as the ZnO content increases from 10 to 30 mol%. Knoop hardness slightly decreases from 307 to 290 kgf/mm2 with increase in ZnO content from 10 to 30 mol% for 10 mol% of MoO3 content, whereas it increases for 20 mol% of MoO3. Based on the results, it concludes that the number of bridging oxygens and network compactness of tellurite matrix increased with increase in ZnO content varied from 10 to 30 mol%.
A series of Er3+/Yb3+ co-doped fluorophosphate glasses with varying YbF3 concentration were prepared by a high temperature melt quenching technique. The effect of sensitization on various spectroscopic properties of Er3+-doped fluorophosphate glasses was investigated. Using the Judd-Ofelt theory, the intensity parameters (Ωλ, λ = 2, 4 and 6) were evaluated from the absorption spectra of glasses. Absorption and emission cross-sections were determined by using the McCumber theory. The dependence of Er3+ ions near infrared emission (1.54 μm) on the Yb3+ concentration was investigated. The upconversion studies were also carried out at room temperature and low temperatures. The wider bandwidth (78 nm), larger emission cross-section (9.86 x 10-21 cm2) and longer fluorescence lifetime (12.37 ms) were noticed for the 4I13/2 → 4I15/2 transition of ABS3Er4Yb glass. The temperature sensing behavior of the ABS3Er5Yb glass was studied by using the fluorescence intensity ratio technique in the temperature range from 100 K to 280 K. The sensitivity and temperature of the maximum sensitivity were found to be of the order of 15 x 10−4 K−1 and 271 K, respectively. The results suggested that the present glass composition has possibilities for optical applications.
An interest of chalcogenide glass has been increased because of their use in preparing optical lenses in range of 3-12 μm.
With recent advance in less costly uncooled detector technology, moldable lens using chalcogenide glass has drawn a
great deal of attention. In this study, amorphous Ge-Sb-Se chalcogenide was prepared by a standard melt-quenching
technique. Melted chalcogenide glass for moldable lens should have unique thermal and mechanic properties in order to
be applied to molding process. Specifically, the Ge:Sb ratio were controlled in order to find out the most stable glass
forming area. Thus, the optical, thermal and thermomechanical properties to find out the specific composition were
characterized by FT-IR spectroscopy, Differential Scanning Calorimeter and Thermo Mechanical Analysis, respectively.
The moldability of chalcogenide glass was characterized through the surface condition of glass samples. Finally, the
preferential Ge:Sb ratio in Ge-Sb-Se based chalcogenide glass system was selected to fabricate moldable lenses.
Chalcogenide glasses have been attracted because of their use in moldable lenses for the application in range of 3-12 μm.
In this study, amorphous Ge-Sb-Se chalcogenide was prepared by a standard melt-quenching technique for moldable lens.
Moldable lens should have unique thermal mechanic properties in order to be applied to molding process. Thus, the
optical and thermal properties to find out right composition were characterized by IR transmission spectroscopy and
DSC, respectively. Specifically, the Ge:Sb ratio were controlled in order to find out the most stable glass forming area.
The relations between thermal properties and the moldability were studied by using an optical microscopy in term of
thermal properties such as Tg and Tx. Transcription properties of the surface of lens or molds were explained in terms of
thermal properties in their composition The preferential Ge:Sb ratio in Ge-Sb-Se based chalcogenide glasses was
selected for producing moldable lens.
In this works, the piezoelectric devices of ZnO nano-rods were fabricated for piezoelectric sensor. The ZnO nano-rods were grown by hydrothermal synthesis through two-dimensional nano-patterns using a laser interference lithography. ZnO nano-rods were preferred orientation with c-axis and wurtzite structure. It was found that the electricity of nano-rod piezoelectric device was 8x10-7 Wh under the load of 0.8kgf. The piezoelectric behaviors are attributed to the direct compression of ZnO nano-rods by an external force. Therefore, the piezoelectric devices of ZnO nano-rods fabricated by hydrothermal methods were applicable to the pressure sensors.
In this works, rare earth ion doped core and core-shell Y2O3 phosphors have been extensively studied for many
applications due to the high stability and emission range and intensity. The core-shell Y2O3: (RE= Eu, Dy, Tb)
nanoparticles are synthesized using a two-step process in which 100-150 nm Y2O3 core particles are synthesized using a
molten salt synthesis and the shell is deposited using a sol-gel process The core-shell architecture was designed for
enhanced luminescence efficiency with long emission lifetimes. Specifically, a multi-shell architecture was necessary to
spatially separate Dy3+, Eu3+ and Tb3+ within the phosphor to circumvent the energy transfer to the surface quenching
sites. First, the crystallinity of Y2O3nanophosphors was characterized using X-ray analysis. RE-doped Y2O3 core
nanoparticles have a good compositional homogeneity. We have also recorded emission spectra and measured
fluorescence lifetime. After coating passive shell layer, emission spectra and measured emission lifetimes were
compared with those form Y2O3 nanophosphor core system and the effectiveness of these core-shell phosphors were
successfully assessed.
Selective patterning of chemical functional groups on polymer surfaces is utilized for controlled placement of monodisperse noble metal nanoparticles. Self-assembled diblock copolymer films deposited on hydrophobic silicon substrates are used as a template for metal nanoparticle organization. By varying the processing conditions of polymer templates, micelle and cylindrical polystyrene-b-poly(methyl methacrylate) diblock copolymer templates were fabricated. Functional groups on the surface of poly(methyl methacrylate) domains in the diblock copolymer films were chemically modified from an ester group to a carboxylate using a base catalyzed hydrolysis step. Gold and silver nanoparticles were fabricated in solution in order to achieve size and shape control. After gold nanoparticle synthesis, a ligand exchange reaction was performed to produce nanoparticles with amine functional groups for chemical attachment on chemically modified poly(methyl methacrylate) surfaces. Atomic force microscopy and scanning electron microscopy images demonstrate that this fabrication route results in preferential attachment of metal nanoparticles on poly(methyl methacrylate) thin films and on poly(methyl methacrylate) domains in polystyrene-b-poly(methyl methacrylate) diblock copolymer thin films.
Judd-Ofelt parameters for Nd3+ ions in a new series of (Mg, Ba)F2-based fluorophosphate glass (the MBBA system) are determined from the intensities of the integrated absorption bands of the Nd3+ ion in the MBBA system. The intensity parameters, Ω2, Ω6, and Ω4 for f-f transitions of Nd3+ ions are found to be -1.02, 10.82, and 4.27 (×1020 cm2), and 1.19, 3.95 and 3.11 in the MBBA/NdI and MBBA/NdII systems, respectively. The measured lifetime τf is 168 μs for the MBBA/NdI system, while the Judd-Ofelt analysis expects a radiative transition lifetime Arad for 4F3/2 to be 316 μs, resulting in a fluorescence quantum efficiency of 47%. The results are compared with those reported in the literature for other fluorophosphate glasses and show that 4F3/2 to 4I11/2 transition has the most potential for laser application with a peak fluorescence at 1056nm.
A new series of fluorophosphate glass is developed which can be doped with an extremely high concentration of Nd3+. The dependence of the optical absorption and emission properties on dopant concentration is reported here for the concentration range 2.5×1020 to 1.25×1021 ions/cm3. Absorption and emission measurements are performed in order to evaluate the spontaneous emission probability, absorption cross-section, emission cross-section, and laser performance parameters. We have synthesized two glass systems: MBBA/NdI with an Nd3+ concentration of 2.50×1020 cm3 and MBBA/NdII with an Nd3+ concentration 6.26×1020 cm3. The stimulated emission cross sections are 1.14 and 1.64×104 cm2 for the 4F3/2→4I13/2 transition and 3.68 and 6.68×104 cm2 for the 4F3/2→4I13/2 transition in MBBA/NdI and MBBA/NdII, respectively. Similarly, the extraction efficiencies are measured to be 1.91, 2.31 (4FI3/2→4I13/2) and 6.18, 9.41 (4F3/2→4I11/2) in MBBA/NdI and the MBBA/NdII, respectively. This new (Mg, Ba)F2-based fluorophosphate glass (MBBA system) is promising for broadband compact optical fiber and waveguide amplifier applications.
Linear and nonlinear refractive index, Abbe number, electronic energy gap and oscillator strength are reported for a new series of (Mg, Ba)F2-based fluorophosphates glasses (MBBA system) doped with rare earth dopants (Er3+, Nd3+) in the concentration range of 6.67×1020 - 2.86×1021 (ions/cm3) and 2.5×1020 - 1.25×1021 (ions/cm3), respectively. The linear refractive index is found to increase with increasing dopant concentration, while the Abbe number is found to be remarkably concentration invariant, i.e., around 66-68 for both dopants. The average electronic band gap is also found to be almost dopant concentration independent, i.e., about 4.1, while the electronic oscillator strength is found to slightly increase with increasing dopant concentration, i.e., from 6.2 to 6.4. The nonlinear refractive index is found to show a linear increase from 1.2866 to 1.4018 for the investigated dopant concentration range. Those results strongly suggest the present new series of glasses can be excellent laser hosts.
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