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.
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.
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.
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.
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