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Analysis of Thermal Aberrations in the Power Amplifiers of a 10-Hz 100-TW Ti:sapphire Laser
성재희,정태문,이성구,유태준,최일우,이종민 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2
We analyze thermally-induced aberrations in the two power amplifiers of a 10-Hz, 100-TW Ti:sapphire laser. The thermal lensing effect, resulting in a focus shift, is investigated by calculating the thermal focal length with the generalized ray-transfer matrix. To characterize the effect of higher-order thermal aberrations, such as coma, trefoil, spherical aberration, and so on, we calculate the beam quality factor, M2, with the wavefront of the laser beam. We show that the induced higher-order thermal aberrations degrade the laser beam quality.
High-quality, 1-kHz, 20-fs, 0.15-TW Ti:sapphire Laser with a Single-stage Amplifier
성재희,유태준,정태문 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.61 No.8
We have demonstrated the generation of 20-fs, 0.15-TW laser pulses with high temporal and spatial qualities from a kHz femtosecond Ti:sapphire laser system with a single-stage amplifier. A maximum output energy of 4.1 mJ could be achieved from the amplifier by suppressing thermal lensing effect. The spectral bandwidth of 57 nm was obtained by maximizing reflection bandwidth that the amplifier could support and by compensating for gain narrowing. The temporal profile close to the Fourier-transform-limited pulse profile was obtained by minimizing the spectral phase error, and the pulse duration was 20 fs at FWHM. The measured beam quality factors were 1.2 and 1.4 in the horizontal and the vertical directions, respectively.
Development of Reversing the Usual Order of Somatic Cell Nuclear Transfer in Mice
강호인,성재희,노상호 사단법인 한국동물생명공학회 2011 한국동물생명공학회지 Vol.26 No.1
Somatic cell nuclear transfer (SCNT) is a useful tool for reproducing genetically identical animals or producing transgenic animals. Many reports have demonstrated that the efficiency of animal cloning by SCNT requires reprogramming of the somatic nucleus to a totipotent like-state. The SCNT-related reprogramming might mimic the natural reprogramming process that occurs during normal mammalian development. However, recent evidence indicates that the reprogramming event by SCNT is incomplete. In this study, the traditional SCNT procedure (TNT) was modified by injecting donor nuclei into recipient cytoplasm prior to the enucleation process to expose the donor nucleus before removing the karyoplast containing the chromosomes of the oocytes which might possess additional reprogramming factors, and this modified technique was named as reversing the usual order of SCNT (RONT). Other procedures including activation and in vitro culture were the same as TNT. Contrary to expectations, the rate of blastocyst development was not different significantly between RONT and TNT (8.6% and 7.9%, respectively). However, duration of micromanipulation performed by the same technician and equipments was remarkably reduced because the ruptured oocytes after nuclear injection were excluded from the enucleation process. This study suggests that RONT, a simplified SCNT protocol, shortens the duration of SCNT procedure and this less time-costing protocol may enable the researchers to perform murine SCNT easier.
CO2 Laser Assisted Fabrication of Micro-lensed Single-mode Optical Fiber
최훈국,손익부,유동윤,노영철,성재희,이성구,정태문,Md. Shamim Ahsan,김진태 한국광학회 2015 Current Optics and Photonics Vol.19 No.4
This paper reports the fabrication of various micro-lensed single-mode optical fibers through the useof an enhanced peak power CO2 laser beam. The end faces of the optical fibers are exposed to the CO2laser beam to form convex, concave, and conical shape optical fiber tips. Peak power of the CO2 laserbeam was varied from 0.8 W to 1.5 W depending on the shape of the optical fiber tip. We also discoverthe dependence of the angle of the optical fiber tip on the rotation angle and the number of CO2 laserirradiations. The angle shows an increasing trend with both these parameters. We achieve a wide rangeof lenticular fibers with end face angle varying from 4.47° to 8.13°. Furthermore, we investigate theemission pattern of light from the developed micro-lensed fibers. The proposed CO2 laser based opticalfiber reshaping technique shows great consistency, and thus is suitable for commercial applications
윤진우,이성구,유태준,성재희,정태문,이종민 한국물리학회 2012 Current Applied Physics Vol.12 No.3
We design a two-stage non-collinear optical parametric chirped pulse amplifier using BBO crystals for a high-power Ti:sapphire laser system, and numerically analyze the output characteristics of the OPCPA system. We find optimal phase-matching conditions and calculate the parametric gains as a function of pump intensity and interaction length. By constructing a two-stage OPCPA system using two BBO crystals, we obtain 12 mJ output energy corresponding to a high gain of 107, a pulse duration of 37 fs, and a contrast ratio of 5×10-8.
Contrast Ratio Improvement by Using Gain Control of the Amplifiers in a 100-TW Ti:sapphire Laser
Seong Ku Lee,유태준,성재희,윤진우,정태문,이종민 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.6
We investigate the temporal profile of a prepulse via amplified spontaneous emission (ASE) in the saturation regime of the amplifier of an ultrashort high power Ti:sapphire laser, which plays an important role in applications of a high peak power laser. We experimentally show that the temporal profile of the ASE prepulse is strongly related to the gain of the amplifier due to the saturation effect. We demonstrate that the contrast ratio can be improved by using gain control of the amplifiers in a 100-TW Ti:sapphire laser.
펨토초 펄스와 광결정 광섬유를 이용한 초 연속스펙트럼의 발생
최형규,김소은,기철식,성재희,유태준,고도경,이종민,Choi, Hyoung-Gye,Kim, So-An,Kee, Chul-Sik,Sung, Jae-Hee,Yu, Tae-Jun,Ko, Do-Kyeong,Lee, Jong-Min 한국광학회 2007 한국광학회지 Vol.18 No.5
광결정 광섬유에서 생성되는 초 연속스펙트럼의 특성을 일반화된 비선형 슈뢰딩거 방정식과 split step 퓨리에 방법을 이용하여 전산모사 하였다. 그 결과를 바탕으로 200 fs 펄스폭을 갖는 Ti:sapphire 레이저와 광결정 광섬유를 이용하여 650nm부터 900nm에 이르는 파장영역에서 ${\pm}4dB$ 이하의 평탄도를 가지는 초 연속스펙트럼을 실험적으로 생성하였다. The characteristics of the supercontinuum generated in photonic crystal fibers were investigated by using the generalized nonlinear $Schr\"{o}dinger$ equation and the split-step Fourier method. Based on the simulated results, we generated the supercontinuum spectrum with the flatness of ${\pm}4dB$ in the wavelength range of 650 to 900 nm by employing a 200-fs pulse of Ti:sapphire laser and a commercial photonic crystal fiber.