Dr. Karam Han Profile

Dr. Karam Han

at Korea Photonics Technology Institute

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Publications (2)

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Proceedings Article | 30 September 2022 Poster + Paper

Study of Ge-As-Se system with high refractive index for infrared glass molded lens

Seon Hoon Kim, Taeyeon Lee, Soyoung Kim, Karam Han, Jung-Hwan In, Doo Gun Kim, Ju Hyeon Choi

Proceedings Volume 12234, 122340F (2022) https://doi.org/10.1117/12.2632956

KEYWORDS: Glasses, Germanium, Refractive index, Infrared lenses, Selenium, Glass molding, Infrared radiation, Thermography, Temperature metrology, Infrared imaging

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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.

Proceedings Article | 30 September 2022 Paper

Development of sealing glass and fiber type sealant for laser sealing

So Young Kim, Ka Ram Han, Seon Hoon Kim, Ju Hyeon Choi

Proceedings Volume 12231, 122310I (2022) https://doi.org/10.1117/12.2632566

KEYWORDS: Glasses, Sodium, Fiber lasers, Absorption, Packaging, Transmittance, Laser applications

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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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