To analyze optical damage of germanium (Ge) induced by a continuous wave (CW) laser, numerical and experimental studies were carried out. Temperature and solid-liquid phase transition with laser conditions were estimated by numerical simulation. In our experiments, we examined morphological changes with hillocks, material changes in the GeO2 layer by oxidation, and new crystal domains formed by recrystallization. The material damage process was explained. Transmittance reduction was also observed in the mid-infrared region. We confirmed that hillock formation, oxidation, and recrystallization through resolidification are critical factors in damaging the optical performance of Ge with a CW laser.

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The objective of this study is to investigate the influence of surface roughness on the morphology of aluminum 6061-T6 alloy after irradiation with a Nd:YAG pulsed laser. The test specimen was prepared by a polishing process using a diamond paste (1 µm) and emery polishing papers (#100, #220, #600, #2400) to obtain different initial surface roughness. After irradiation with ten pulsed-laser shots, the surface morphology was examined by using scanning electron microscopy (SEM), optical microscopy (OM), and atomic force microscopy (AFM). The diameter of the melted zone increased with the surface roughness because the multiple reflections and absorption of the laser beam occurred on the surface because of the surface roughness, so that the absorptance of the laser beam changed. This result was verified using the relative absorptance calculated from the diameter of the melted zone with the surface roughness and the diameter increased with the average surface roughness.

서 론근적외선대역의 고출력 레이저를 무기로 활용하 기 위한 연구가 활발히 진행되고 있다. 레이저 무 기의 장점은 광속으로 매우 빠르게 목표에 도달할 수 있고, 목표 지점을 국부적으로 정밀하게 타격 할 수 있다. 또한, 전자기장의 영향도 받지 않고, 레이저의 발사 지점을 은닉하기 쉽다.(1) 특히, 근 적외선대역 파장의 레이저는 공기 중의 산란이나 흡수가 작아 먼 거리를 전파할 수 있기 때문에 레 이저 무기로 활용하기에 적합하다. Abstract: This paper presents the results of an experimental analysis of the high-power laser (HPL)-induced damage to a complementary metal-oxide semiconductor (CMOS) image sensor. Although the laser-induced damages to metallic materials have been sufficiently investigated, the damages to electric-optic imaging systems, which are very sensitive to HPLs, have not been studied in detail. In this study, we experimentally analyzed the HPL-induced damages to a CMOS image sensor. A near-infrared continuous-wave (CW) fiber laser was used as the laser source. The influences of the irradiance and irradiation time on the permanent damages to a CMOS image sensor, such as the color error and breakdown, were investigated. The experimental results showed that the color error occurred first, and then the breakdown occurred with an increase in the irradiance and irradiation time. In particular, these damages were more affected by the irradiance than the irradiation time. § 이 논문은 2014 년도 대한기계학회 신뢰성부문 춘계학술대회

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