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Widely Tunable Grating Cavity Lasers
권오기,김강호,김종호,오광룡,심은덕,윤호경,O Kyun Kwon 한국전자통신연구원 2006 ETRI Journal Vol.28 No.5
A widely tunable multi-channel grating cavity laser is proposed and experimentally demonstrated. The device is implemented in Littman configuration with an echelle grating based on Rowland circle construction and realized by monolithically integrating all elements in an InP substrate. Lasing wavelength is selected by turning on an amplifier and the appropriate channel element in the array, and it is tuned by controlling light deflection electrically. The 6-channel device exhibits a tuning range of about 50 nm with a side mode suppression ratio of more than 30 dB. This is accomplished by adjusting the applied current of the dispersive element and phase control section.
권오기,백용순,정윤철,박형무 한국전자통신연구원 2013 ETRI Journal Vol.35 No.3
A novel integrated laser, that is, a distributed reflector laser diode integrated with an electroabsorption modulator, is proposed to improve the output efficiency, single-mode stability, and chirp. The proposed laser can be realized using the selective metalorganic vapor phase epitaxy technique (that is, control of the width of the insulating mask), and its fabrication process is almost the same as the conventional electroabsorption modulated laser (EML) process except for the asymmetric coupling coefficient structure along the cavity. For our analysis, an accurate time-domain transfer-matrix-based laser model is developed. Based on this model, we perform steady-state and large-signal analyses. The performances of the proposed laser, such as the output power, extinction ratio, and chirp, are compared with those of the EML. Under 10-Gbps NRZ modulation, we can obtain a 30% higher output power and about 50% lower chirp than the conventional EML. In particular, the simulation results show that the chirp provided by the proposed laser can appear to have a longer wavelength side at the leading edge of the pulse and a shorter wavelength side at the falling edge.
권오기,심재설,이홍식 중앙대학교 건설환경연구소 2001 環境科學硏究 Vol.12 No.1
The numerical model is presented for the prediction of wave fields in a harbor with partially reflecting boundaries. The water depth is assumed to be constant, and the solution was obtained by the boundary element approach. The present numerical study is based on the linear diffraction theory with regular waves. The results of the present model have been compared with the results of previous physical modeling. Good agreement was obtained in all cases. Based on these comparisons, the present numerical model is and accurate and efficient tool to predict the wave fields in a harbor with partially reflection boundaries in constant water depth.
권오기,오창완,정영섭,한대희 대한신경외과학회 1996 Journal of Korean neurosurgical society Vol.25 No.9
The purpose of this study was to understand the general features of pulmonary embolism in neurosurgical patients. The authors retrospectively reviewed 24 cases of pulmonary embolism from 1981 to 1994. The overall incidence of pulmonary embolism was 0.2%, but in the most prevalent year(1994) it was 1.3%. Lower extremity weakness and immobilization was the most common predisposing condition. Of 24 patients with pulmonary embolism, 23 patients showed lower extremity weakness, and the mean duration of immobilization was 47 days. Most patients (80%) had symptoms of pulmonary embolism within 4 weeks after operation. Medical prophylactic method had not been used in patients other than physical prophylactic method-graduated compression stocking. position change or physical therapy. Heparinization was given to 18 patients(75%), and minor hemorrhagic complication developed in 2 patients, but no major bleeding occurred. Inferior vena cava filter was applied in 2 patients. Only one patient suffered from recurrence and it was not fatal. Of the 24 patients. 7 died, however only one patient died of pulmonary embolism. In our study, the prognosis of pulmonary embolism was not as serious as it has been reported in the literature. However, more precise studies will be needed to understand the fate of pumonary embolism in Korean neurosurgical patients.