• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.8
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• pp.2029-2036
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• 2014

The performance analysis of optoelectronic oscillator(OEO) based on a directly modulated semiconductor laser was theoretically achieved. First, the analysis was performed on the open response of the key components that constitute the OEO loop. Using the results, we simulated the open-loop characteristics of the OEO loop. By combining oscillation conditions of loop oscillator in addition to the open-loop magnitude and phase responses, theoretical performance analysis such as OEO's oscillation frequency, spurious tones and phase noise was successfully completed.

• Proceedings of the Optical Society of Korea Conference
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• 2009.10a
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• pp.185-186
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• 2009

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.99-103
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• 2005

In this paper, a new technique to reduce the phase noise in microwave oscillators is proposed using the resonant characteristics of the Photonic Bandgap(PBG). We applied PBG structure to ground of the microstrip line resonator with the low Q(Quality factor). Therefore, we improved about 10 dBc in contrast to phase noise characteristic of the conventional microstrip line oscillator at 2.4 GHz ＠ 100 MHz offset. Output power is 7.09 dBm.

• Korean Journal of Optics and Photonics
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• v.32 no.5
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• pp.209-214
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• 2021

High-power continuous-wave operation of a Yb-doped double-clad fiber laser at 1018 nm, pumped by high-power diode lasers at 976 nm, is reported. Based on numerical calculation of the gain and laser signal power along the length of the Yb fiber, it is found that robust operation at 1018 nm can be achieved for a high Yb³⁺-ion excitation density greater than 11.5%, accompanied by high suppression of the feedback from the fiber's end facet. The Yb fiber laser constructed in house yields 626 W of continuous-wave output at 1018 nm for 729 W of incident pump power, corresponding to a slope efficiency of 86.6%. The prospect for power scaling is considered.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.5
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• pp.1304-1316
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• 1996

In this paper, A VCO(Voltage Controlled Oscillator) in use of clock recovery/data regeneration circuit for 10 Gbps fiber optic receivers was developed. The improved hair-pin resonator with a parallel coupled lines, which has been applied to microstrip filters, was used as a resonance part. As a frequcncy tuning device by substituting 3-terminalMESFET vaaractor for varactor diode, an MMIC manufacturing process will be simplified. Since a hair-pin resonator is planar type compared to the dielectric resonator and has a relatively flat reactance verus frequency, it will be favorable to apply a hair-pin resonator to an MMIC, in addition wideband frequency tuning range is able to be obtained.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.418-422
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• 1994

본 연구에서는 MOVPE를 이용한 MQW활성층을 DFB-LD 구조에 도입함으로서 2.5Gbps 광전송용 광원으로 사용된 $ 1.55.\mu$m 파장의 MQW-PBH-DFB-LD를 제작하였다. 활성층으로는 MOVPE를 이용하여 8쌍의 InGaAs/InGaAsP MQW층을 성장하였으며 2차 및 3차 결정성장은 LPE를 사용하였고 발진파장을 결정하는 회절격자 주기는 238nm로 하였다. MQW-PBH-DFB-LD의 평균 임계전류는 13.81mA, Slope efficiency는 0.137mW/mA이었고 발진파장은 1548.6nm의 특성을 얻었다. 그리고 2.5Gbps 대신호 변조시의 chirping특성을 조사하여 본 결과 0.55nm임을 확인할 수가 있었다.

• Korean Journal of Optics and Photonics
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• v.32 no.4
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• pp.147-152
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• 2021

We report high-power continuous-wave operation of a Yb-doped fiber laser at 1070 nm, pumped by high-power laser diodes at 976 nm. Based on theoretical calculation of the stimulated Raman scattering and temperature distribution in the fiber, we construct a bidirectionally pumped Yb-fiberlaser system incorporating a pair of fiber Bragg gratings and a cladding light stripper. The fiber laser yields 3.0 kW of continuous-wave output at 1070 nm in a diffraction-limited beam with M² ≈ 1.26 for 4.1 kW of incident pump power, corresponding to a slope efficiency of 81.5%. The prospects for further power scaling are discussed.

• New Physics: Sae Mulli
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• v.68 no.12
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• pp.1374-1377
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• 2018

We achieved 95% visibility in the Hong-Ou-Mandel interference experiment while we achieved only 56% visibility in a previous report. We used a 120 mW 405 nm single-mode continuous wave laser, a 5-mm-thick type-1 ${\beta}$-barium borate single crystal, standard Hong-Ou-Mandel interferometer optics, two avalanche photodiode single-photon counters, and a homemade coincidence counting unit. The photon collection unit was the key difference between the present study and the previous study. In the present experiment, we used single-mode optical fibers for photon collection, which suppressed accidental coincidence between-different mode photons by acting as a spatial filter because of its core size being much smaller than a multi-mode fiber.