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양정택,김영현,마지 퍼니,이재봉,방동수,김태경,최우영 한국광학회 2019 Current Optics and Photonics Vol.3 No.5
The influence of high-power laser diode (HPLD) emitter width on the device performance is investigated for 975-nm (In,Ga)(As,P)/(Al,Ga)As broad-area HPLDs, using self-consistent electro-thermal-optical simulation. To guarantee the simulation’s accuracy, simulated results are matched with the measured results for a sample HPLD with fitting parameters. The influences of HPLD emitter width on temperature distribution, output power, and the beam product parameter (BPP) are analyzed for three different emitter widths of 50, 70, and 90 µm. It is found that a device with smaller emitter width exhibits both thermal rollover and thermal blooming at lower output power, but smaller BPP.
Lateral Far-field Characteristics of Narrow-width 850 nm High Power GaAs/AlGaAs Laser Diodes
양정택,곽정근,최안식,김태경,최우영 한국광학회 2022 Current Optics and Photonics Vol.6 No.2
We investigate the lateral far-field pattern characteristics, including divergence angle change and farfield pattern analysis as output power increases, of narrow-emitter-width 850 nm GaAs/AlGaAs laserdiodes (LDs). Each LD has a cavity of 1200 and 1500 μm and narrow emitter width of 2.4 μm for the top and 4.6 μm for the bottom. The threshold currents are 35 and 40 mA, and L-I kinks appear at powerlevels of 326 and 403 mW, respectively. The divergence angle tends to increase due to the occurrence of first-order lateral mode and the thermal lensing effect. But with the L-I kink, the divergence angle decreases and the far-field pattern becomes asymmetric. This is due to coherent superposition between the fundamental and the first-order lateral mode. We provide detailed explanations for these observations based on high-power laser diode simulation results.
Deep Learning-based Extraction of Auger and FCA Coefficients in 850 nm GaAs/AlGaAs Laser Diodes
양정택,한혜원,최우영 한국광학회 2024 Current Optics and Photonics Vol.8 No.1
Numerical values of the Auger coefficient and the free carrier absorption (FCA) coefficient are extracted by applying deep neural networks (DNNs) to the L-I characteristics of 850 nm GaAs/AlGaAs laser diodes. Two elemental DNNs are used to extract each coefficient sequentially. The fidelity of the extracted values is established through meticulous correlation of L-I characteristics bridging the realms of simulations and measurements. The methodology presented in this paper offers a way to accurately extract the Auger and FCA coefficients, which were traditionally treated as fitting parameters. It is anticipated that this approach will be applicable to other types of opto-electronic devices as well.
850 nm GaAs/AlGaAs MQW LD의 Lateral-mode 특성 연구
양정택,곽정근,최안식,김태경,최우영,Yang, Jung-Tack,Kwak, Jung-Geun,Choi, An-Sik,Kim, Tae-Kyung,Choi, Woo-Young 한국광학회 2021 한국광학회지 Vol.32 No.2
850 nm 대역의 발진 파장을 갖는 GaAs/AlGaAs 다중양자우물 레이저 다이오드의 lateral-mode 특성과 이 특성이 출력 광파워 kink에 미치는 영향을 조사하였다. 이를 위해 전기적-열적-광학적 시뮬레이션을 self-consistent하게 수행하고, 제작된 레이저 다이오드 소자들을 측정하였다. 연구 결과를 바탕으로 높은 출력 파워에서도 single lateral-mode를 유지해서 좋은 beam quality를 유지할 수 있는 최적의 P-cladding 두께를 결정하였다. The lateral-mode characteristics of 850-nm GaAs/(Al,Ga)As multiple-quantum-well laser diodes and their influence on the kinks in output optical power are investigated. For the investigation, self-consistent electro-thermal-optical simulation and measurement of fabricated devices are used. From this investigation, the optimal P-cladding thickness that provides single-lateral-mode operation is determined, so that high beam quality can be achieved even at high output powers.
양세정,김태년,백세현,김태선,이관우,남문석,박용수,우정택,김영설,김성훈 대한내과학회 2013 The Korean Journal of Internal Medicine Vol.28 No.3
Background/Aims: The aim was to compare the insulin sensitivity and secretion index of pregnant Korean women with normal glucose tolerance (NGT), gestational impaired glucose tolerance (GIGT; only one abnormal value according to the Carpenter and Coustan criteria), and gestational diabetes mellitus (GDM). Methods: A cross-sectional study was performed with 1,163 pregnant women with positive (1-hour plasma glucose ≥ 7.2 mmol/L) in a 50-g oral glucose challenge test (OGCT). The 100-g oral glucose tolerance test (OGTT) was used to stratify the participants into three groups: NGT (n = 588), GIGT (n = 294), and GDM (n = 281). Results: The GDM group had higher homeostasis model assessment of insulin resistance and lower insulin sensitivity index (ISOGTT), quantitative insulin sensitivity check index, homeostasis model assessment for estimation of index β-cell secretion (HOMA-B), first and second phase insulin secretion, and insulin secretion-sensitivity index (ISSI) than the NGT group (p ≤ 0.001 for all). Moreover, the GIGT group had lower ISOGTT, HOMA-B, first and second phase insulin secretion,and ISSI than the NGT group (p < 0.001 for all). Among the GIGT subjects, the 1-hour plasma glucose abnormal levels group showed significantly greater weight gain during pregnancy and higher values in the 50-g OGCT than the other two groups. Moreover, the 1-hour and 2-hour abnormal levels groups had poorer insulin secretion status than the 3-hour abnormal levels group. Conclusions: Korean women with GDM show impairments of both insulin secretion and insulin sensitivity. In addition, GIGT is associated with both β-cell dysfunction and insulin resistance.
자가면역성 갑상선 질환에서 B형간염 바이러스 감염의 병인론적 역할
김진우,양형인,최영길,김영설,김광원,양인명,김성운,우정택 대한내분비학회 1991 Endocrinology and metabolism Vol.6 No.4
Although pathogenesis of autoimmune thyroid disease is not clearly defined, the possible role of viruses as the cause of autoimmune thyroid disease was suggested. In 1988, Klavinskis et al reported that lymphocytic choriomeningitis virus can persist in the thyroid gland, concomittent with the infection of these cells was a significant reduction in the level of thyroglobulin mRNA and circulating thyroid hormone. So, to evaluate the possible involvement of viruses in the pathogenesis of autoimmune thyroid disease, we compared the prevalence of the hepatitis B virus markers (HBsAg, anti-HBs, anti-HBc) among thyroid disease; 50 patients of Graves' disease, 40 patients of primary hypothroidism, 12 patients of euthyroid goiter and 40 cases of normal controls. The prevalence of the thyroglobulin antibody (TGAB) and microsomal antibody (MCAB) in chronic B viral hepatitis were also evaluated. The results were follows; 1) there was no significant difference in the prevalence of hepatitis B viral markers between each thyroid disease and control (Graves' disease 8.0%, primary hypothyroidism 2.4%, euthyroid goiter 3.3% control 6.7%) 2) No difference in thyroglobulin antibody and microsomal antibody in chronic B viral hepatitis (TGAB 2.3%, MCAB 4.7%) and general population in Korea. We concluded that hepatitis B virus was probably not role in pathogenesis of autoimmune thyroid disease (J Kor Soc Endocrinol 6:348~352, 1991).
성장장애 환아에서 성장호르몬 치료후 IGF-1 , IGF Binding Protein 3(IGFBP-3) 및 골대사 지표들의 변화에 대한 연구
김진우,양형인,최영길,김영설,양인명,우정택,김성운,김덕윤,한기옥 대한내분비학회 1994 Endocrinology and metabolism Vol.9 No.4
The effects of growth hormone(GH) deficiency and recombinant human GH replacement(0.5IU/kg per week) on bone mineral metabolism in 21GH-deficiency children were studied. All children had significantly reduction of bone density(Z score;-1.4+-0.71). After 1 month of therapy, the levels of serum insulin-like growth factor 1(IGF-1), osteocalcin(OC) and carboxyterminal propeptede of type 1 procollagen(PICP) were significantly elevated. But IGFBP-3 were not shown to change significantly. The changes in serum levels of PICP during the first month of recombinant human GH treatment were positively related to growth velocity, whereas the changes in IGF-1 and OC during the first month of therapy were not. We conclude that the recombinant human GH treatment caused significant modifications of mineral metablism and that the measurement of the changes of biochemical markers of bone metablism espacially PICP may be a useful tool in prediction improved growth velocity during long term GH replacement therpy(J Kor Soc Endocrinol 9: 344-349, 1994).