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온도구배에 의한 고출력 광섬유 레이저의 유도 브릴루앙 산란 억제 특성
정성묵,김기혁,이성헌,황순휘,양환석,문병혁,전영민,박민규,이정환 한국광학회 2019 한국광학회지 Vol.30 No.4
In this paper, we studied characteristics of stimulated Brillouin scattering (SBS) suppression in high-power fiber lasers by using apparatuses applying a temperature gradient (i.e. a step, a sine shape, and random temperature distribution) along the fiber. From the ytterbium-doped polarization-maintaining fiber master oscillator power amplifier built in house, we measured the back-reflection spectrum and power for each temperature gradient, showing that the step shape temperature distribution was the most effective way to suppress SBS. In addition, we investigated the interaction of pseudo-random binary sequence phase modulation conditions and temperature gradients for SBS suppression.
전광섬유 MOPA 시스템 기반 10 GHz 선폭을 갖는 1.5 kW 단일모드 이터븀 첨가 편광유지 광섬유 레이저
정성묵,김기혁,김태균,이성헌,양환석,이준수,이광현,이정환,조민식 한국광학회 2020 한국광학회지 Vol.31 No.5
In this paper, we have studied the characteristics of stimulated Brillouin scattering (SBS) and mode instability (MI) in a ytterbium-doped polarization-maintaining fiber laser with master oscillator power amplifier configuration. We measured the laser output power and back-reflection spectrum for a variety of ytterbium-doped fibers and seed lights, to investigate the power-scaling limits of fiber lasers. By optimizing the laser structure, we demonstrated an all-fiber high-power polarization-maintaining fiber laser with near-diffraction-limited beam quality. The output power of 1.5 kW was achieved with a linewidth of 10 GHz, generated by pseudo-random binary sequence (PRBS) phase modulation. The beam quality M 2 was about 1.15 at the maximum output power. The polarization extinction ratio (PER) was greater than 17 dB.
표면거칠기를 가진 유리의 입자충격 손상기구에 관한 실험적 연구
서창민,정성묵,이문환,Suh, Chang-Min,Chung, Seong-Muk,Lee, Mun-Hwan 대한기계학회 1996 大韓機械學會論文集A Vol.20 No.7
The damage mechanism by the impact of steel ball on the soda-lime glass having a different surface roughness was investigated. An initiation and a propagation behavior of cracks formed by each impact velocity were quantitatively studied. A 4-point bending test was carried out to evaluate the remaining bending strength of a scratched soda-lime glass which impacted by the steel ball. As the surface roughness was increased, the shape of cracks became more irregular rather than those of the smooth specimens. The phenomenon of turning up in the wing of cone cracks occurred even at the lower velocity than the critical velocity caused the crushing. The threshold velocity of cracks initiation generally became lower than those of smooth specimen. An initiation and a propagation behavior of radial cracks had no relation with the direction of scratch on the surface. The remaning benidng strength of the scratched specimen according to impact velocity had no big difference compared with those of the smooth specimen.
최을수,정성묵,김방현,김채옥,김대용,권오경,이창우 한국임상수의학회 2002 한국임상수의학회지 Vol.19 No.4
A 7 year-old male Maltese dog was referred to Seoul National University Veterinary Medical Teaching Hospital with a recurrent mass in the right scapular region. The patient had no pains associated with the mass. On aspiration cytology, the neoplastic mass is composed of clusters of mature adipocytes with large lipid vacuoles, intermixed with frequent microcapillary vessels which is characteristic of lipoma. At surgery, the mass was infiltrated into the surrounding muscles and therefore the complete resection of the mass was difficult. Histologically, the mass was diagnosed as infiltrative lipoma. The patient has no recurrent signs 8 months after surgery
펌핑 구조에 따른 1 kW급 협대역 편광 유지 광섬유 레이저의 출력 특성 연구
김태형,정성묵,김기혁,이성헌,양환석,Kim, Tae Hyoung,Jeong, Seong Mook,Kim, Ki Hyuck,Lee, Sung Hun,Yang, Hwan Seok 한국광학회 2021 한국광학회지 Vol.32 No.4
본 논문에서는 주 증폭기가 양방향 펌핑 방식인 MOPA (master oscillator power amplifier) 협대역 고출력 광섬유 레이저를 제작하였으며, 제작된 레이저의 출력 특성을 연구하였다. 이터븀이 도핑된 코어 25 ㎛, 클래드 400 ㎛ 편광 유지 광섬유를 사용하여 주 증폭부를 제작하였으며, 신호 광원은 PRBS (pseudo-random binary sequence) 신호에 의해 위상 변조된 3 GHz, 10 GHz의 선폭을 갖는 광원을 사용하였다. 3 GHz의 선폭을 가진 신호 광원을 이용하여 순방향과 역방향 펌프 비율을 조절하며 SBS (stimulated Brillouin scattering) 특성을 분석하였다. 10 GHz의 선폭을 가진 신호 광원을 이용하여 주 증폭기의 펌핑 비율에 따른 TMI 특성을 분석하였다. 순방향 및 역방향 펌프 비율을 1.6:1로 입사시켰을 때 주 증폭기의 출력을 1 kW까지 증폭하였으며, 기울기 효율과 빔 품질(M<sup>2</sup>)은 각각 80%, 1.36으로 측정되었다. This paper presents a study of laser output characteristics. We fabricated a MOPA (master oscillator power amplifier)-type high-power, narrowbandwidth fiber laser with a bidirectional pumping configuration in its main amplifier. As signal beams, light sources with bandwidths of 3 GHz and 10 GHz-phase-modulated through a PRBS (pseudo-random binary sequence)-were used interchangeably. Furthermore, the characteristics of the SBS (stimulated Brillouin scattering) were analyzed using a signal beam with 3 GHz bandwidth, by adjusting the forward to backward pumppower ratio. Moreover, the characteristics of the transverse mode instability were analyzed by adjusting the forward to backward pump-power ratio, using a signal beam with 10-GHz bandwidth. Finally, the output power from 10 GHz bandwidth was amplified to more than 1 kW using a forward to backward pump-power ratio of 1.6. The beam quality M<sup>2</sup> was measured to be approximately 1.36, and the optical-to-optical efficiency was 80% at maximum output power.
이복희,문윤성,정성묵 충남대학교 의과대학 지역사회의학연구소 1982 충남의대잡지 Vol.9 No.2
Sixty seven patients with primary extrahepatic malignancy and documentation of the presence or absence of hepatic metastases were selected for study. Tie results were summerized as follow: 1. Twenty one of 67 patients were documented presence of hepatic metastasis. 2. Hepatomegaly on physical examination were detected in 71.4% of patient with hepatic metastasis. 3. Serum alkaline phosphatase elevation were observed in 38.1% of patient with metastasis and in 13.0% of patient without metastasis. 4. Abnormal value of serum AFP were revealed in 14.3% of patient with metastasis and in 4.3% of patient without metastasis 5. Patient with serum CEA value greater than 9.0ng/ml were calculated in 87.5% of metastasis and in 37.5% of non-metastasis.
Large Cell Calcifying Sertoli Cell Tumor of the Testis: A Case Study and Review of the Literature
송대현,이종실,정성묵,박종탁,윤각원,김병권 대한병리학회 2014 Journal of Pathology and Translational Medicine Vol.48 No.1
A 24-year-old man was admitted due to an incidentally detected mass in his left testis, which showed radiopaque calcification on plain X-ray film. Left orchiectomy was performed, and the resected testis contained a well-demarcated, hard mass measuring 1.1 cm. Histological analysis revealed that the tumor was composed of neoplastic cells, fibrotic stroma, and laminated or irregularly shaped calcific bodies. The individual cells had abundant eosinophilic or clear cytoplasm with round nuclei, each of which contained one or two conspicuous nucleoli. They were arranged in cords, trabeculae, clusters, and diffuse sheets. There were several foci of intra-tubular growth patterns, with thickening of the basal lamina. Immunohistochemically, the neoplastic cells were positive for S-100 protein and vimentin, focally positive for inhibin alpha, and negative for cytokeratin, CD10, and Melan-A. In addition to reporting this rare case, we also review the relevant literature regarding large cell calcifying Sertoli cell tumors.