Deep-sea optical windows must withstand extreme hydrostatic pressure while maintaining optical transmittance, requiring a balance between mechanical rigidity and optical performance. Increasing thickness enhances structural strength but reduces transmittance. This study proposes a design method for deep-sea optical windows using domestically developed sapphire. Three-point bending tests were conducted on sapphire and silicon specimens, and B-criterion strength was derived using Weibull distribution to account for brittle material properties. Optical transmittance measurements established key design characteristics. Using theoretical formulations for rectangular planar optical windows under uniform external pressure, the initial design was based on experimentally derived sapphire properties. Finite element analysis of the optical window assembly confirmed sufficient structural stability margins above critical thresholds. Linear interpolation was applied to evaluate the continuous design space across discrete thickness values. A compromise solution was identified that satisfies both structural rigidity and transmittance objectives. By integrating experimental material characterization with numerical analysis, this study provides an effective framework for determining the optimal thickness of deep-sea optical windows and confirms the applicability of domestically developed sapphire as a reliable optical window material for high-pressure underwater environments.
This study experimentally investigates the laser-assisted diamond turning of high-hardness sapphire to enhance its precision machinability for defense optical components. Sapphire is an attractive material for applications such as transparent armor, sensor windows, and optical apertures due to its excellent mechanical strength, thermal and wear resistance, and outstanding optical transparency. In this research, precision cutting tests were performed on a diamond turning machine, and the resulting surfaces were characterized using a white-light interferometric profilometer. At an optimal laser power of 5 W, the surface roughness and form accuracy improved to 28.8 nm Ra and 191 nm RMS, respectively, demonstrating that laser assistance can significantly enhance surface quality. Microscopic observations after processing revealed a noticeable reduction in tool wear under laser-assisted conditions, which is likely to improve process stability and extend tool life. However, both insufficient and excessive laser power resulted in degraded surface quality compared to conventional turning, underscoring the importance of optimizing laser power. These findings highlight the potential for process optimization in laser-assisted diamond turning to improve the precision and reliability of sapphire machining, contributing to the future development of advanced manufacturing technologies for high-precision defense components.
Structural Analysis Study for Performance Enhancement of 3D-printed CANSAT Structures Youngmo Seong, Eungdo Kim, Hyochang Lee, Jinsung Rho, Changbeom Choi Journal of the Korean Society for Precision Engineering.2026; 43(6): 653. CrossRef
In the optical systems field, key components such as spectroscopic elements often require the use of optical materials with high-refractive indices to achieve miniaturization and lightweight characteristics. However, high-refractive index optical materials have low machinability due to their brittle characteristic. In this study, we investigated the changes in surface characteristics during precision pattern machining of high-refractive index materials; specifically, a low fracture toughness, for use in grating spectroscopic elements. The experiment involved diamond turning for the primary machining, and for the secondary pattern machining, the tool rake angle, tool feed rate, and depth of cut were set as variable conditions. Surface roughness measurements and surface quality analyses were carried out using a white-light interferometer and tool microscopy. The results provide insights into the influence of conditions on the surface properties during the machining of high-refractive index materials for grating spectroscopic components. Under the machining conditions with a tool rake angle of -65o, tool feed rate of 5,000 mm/min, and a depth of cut 10 nm, the surface roughness of Ra 8.0 nm was achieved. Based on these findings, we plan to conduct further research on the mechanical fabrication of the blaze angle for grating spectroscopic components.
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Maskless mechanical structuring of thermally annealed ITO electrodes for transparent thin-film transistors Seung-Hun Lee, Hae-In Hwang, Soeun Choi, Ahyun Park, Jihun Ha, Jae Woong Lee, Yeong-Eun Yoo, Min Hwan Lee, Jeong Hwan Kim Surfaces and Interfaces.2026; 95: 109669. CrossRef
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