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Coherent supercontinuum generation using Er-doped fiber laser of hybrid mode-locking.
Kim, Seungman,Park, Jiyong,Han, Seongheum,Kim, Young-Jin,Kim, Seung-Woo Optical Society of America 2014 Optics letters Vol.39 No.10
<P>Supercontinuum generation is performed using femtosecond laser pulses produced by combining two distinct mode-locking mechanisms of nonlinear polarization evolution with saturable absorption on an Er-doped fiber oscillator. The generated supercontinuum yields a high level of spectral visibility of 93%, without the presence of spontaneous emission of post-amplification, being well suited for precision spectroscopy, broadband interferometry, and coherent telecommunications.</P>
Hybrid mode-locked Er-doped fiber femtosecond oscillator with 156 mW output power.
Kim, Seungman,Kim, Yunseok,Park, Jiyong,Han, Seunghwoi,Park, Sanguk,Kim, Young-Jin,Kim, Seung-Woo Optical Society of America 2012 Optics express Vol.20 No.14
<P>We report on an Er-doped fiber oscillator that produces 146 fs pulses with 156 mW average power at a repetition rate of 49.9 MHz. The pulse energy reaches 3.13 nJ, surpassing the conventional power limit in the dispersion-managed soliton regime. Such high pulse power is obtained by devising a hybrid mode-locking scheme that combines saturable absorption with nonlinear polarization evolution. The oscillator also offers excellent temporal purity in the generated pulses with high power, providing a robust fiber-based frequency comb well suited for industrial uses.</P>
Er-doped fiber frequency comb with mHz relative linewidth
Kim, Yunseok,Kim, Seungman,Kim, Young-Jin,Hussein, Hatem,Kim, Seung-Woo The Optical Society 2009 Optics express Vol.17 No.14
<P>A low-noise fiber frequency comb is demonstrated to improve the frequency accuracy and linewidth by suppressing the phase noise caused by the nonlinear self-phase modulation as well as the amplified spontaneous emission within the Er-doped fiber amplifier. The linewidth of the carrier-envelop- offset signal measures less than 1.9 mHz and the frequency stability well follows the reference Rb clock. This achievement will facilitate the use of the fiber frequency comb for industrial applications to precision near-infrared spectroscopy, frequency calibration, optical clocks and length metrology.</P>
Er-doped fiber comb with enhanced f_ceo S/N ratio using Tm:Ho-doped fiber
Kim, Yunseok,Kim, Young-Jin,Kim, Seungman,Kim, Seung-Woo The Optical Society 2009 Optics express Vol.17 No.21
<P>We report that the Tm:Ho-doped fiber can be utilized to improve the frequency stabilization of the Er-doped fiber comb. This rare-earth doped fiber provides photon absorption at 1.2 microm and 1.7 microm wavelengths together with emission at wavelengths between 1.8 microm to 2.1 microm. This unique combination of the absorption and emission regions constructively redistributes the spectral power of the supercontinuum generated by a highly nonlinear fiber to detect the carrier-envelope-offset frequency (f(ceo)) via a self-referencing f-2f interferometer. As a result, the signal to noise (S/N) ratio of the detected f(ceo) signal increases by 10 dB, thereby increasing the potential of enhancing the long-term frequency stability of the fiber frequency comb.</P>
김영진(Young-Jin Kim),김윤석(Yunseok Kim),김승만(Seungman Kim),김승우(Seung-Woo Kim) Korean Society for Precision Engineering 2010 한국정밀공학회지 Vol.27 No.6
Physical fundamentals of ultrashort femtosecond lasers are addressed along with emerging applications for precision manufacturing and metrology. Femtosecond lasers emit short pulses whose temporal width is in the range of less than a picosecond to a few femtoseconds, thereby enabling extremely high peak-power machining with less thermal damages. Besides, the broad spectral bandwidth of femtosecond lasers constructed in the form of frequency comb permits absolute distance measurements leading to ultraprecision positioning control and dimensional metrology.
서호종,김기훈,박성호,최진욱,김광석,고성만,서광섭,김홍자,김호정,허병원,김해경 중앙대학교 의과대학 의과학연구소 2001 中央醫大誌 Vol.26 No.3
Ulcerative colitis(UC)is a disease that affects the mucosal lining of the colon. Epidemiologlcal studies revealed that UC is global in distribution and the incidence has risen in recent decades. The pathogenesis of UC, remains uncertain. However, recent studies have suggested that colonic environment, most notably bacteria flora, genetic susceptibility, mucosal defects, immunologic abnormalities, altered levels of specific cytokine and inflammatory mediators,and dietary factors are implicated. The major symptoms of ulcerative colitis include diarrher, abdominal pain, and hematochezia(rectal bleeding). Ulcerative colitis also may be complicated by many local and systemic disorders as extracolonic symptoms. Erythema nodosum is one of the most frequent dermatologic complications associated with ulcerative colitis. It is an acute, painful, rective skin inflammation of unknown cause. Physicians can disgnose clinically, since there is no accepted histological diagnostic criteria. Conventational therapy is preferred to control causative disease. We authors experienced a case of suppurative erythema nodosum on both shins of ulcerative colitis patient, which was treated with high dose corticosteroids and discharged with clinical improvement of dematologic manifiestation, coincidently controlled acute exacerbation of the bowel disease. So we report this case with a brief literature review.