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Measurement of the Birefringence in Bulk Optical Media by Using Interferometric Methods
차명식,최희주,임환홍,김병주 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6
Accurate knowledge of the index of refraction of an optical medium is of fundamental impor- tance in various optical applications. We applied a Michelson interferometer and Fabry-Perot-type interference methods to a wafer sample to estimate the difference between two orthogonal indices, Δn, of a LiNbO3 crystal wafer and we compared the results of the two methods. By measuring the transmittance with sample rotation, we obtained a beat pattern between the fringes of the ordinary and the extraordinary light waves. Fitting the node locations, we could determine the Δn value with an uncertainty of 10-3 with both methods. Since the Fabry-Perot method is insensitive to atmospheric turbulence and vibration and is very simple to implement, it alow a quick estimate of the birefringence in optical crystals.
Group Velocity Matched Second Harmonic Generation in Periodically Poled Potassium Niobate
차명식,유난이,Sunao Kurimura,Kenji Kitamura,Satoshi Ashihara,Takayuki Ohta,Tsutomu Shimura,Kazuo Kuroda,Oc-Teob Jeon 부산대학교 유전체물성연구소 2004 유전체 논문집 Vol.3 No.
We investigated the group velocity matched second harmonic generarion in periodically poled potassium niobate. The QPM wavelength bandwidth was 38 nm around 1520 nm at 35℃ in 14.4㎛ QPM period with 10.5 mm interaction length. We also observed ultra-fast pulse used type-ⅠSHG conversion efficiency. The SHG conversion efficiency of the PPKN crystal was about 3 times that of type-Ⅰ SHG in PPMgLN.
Michelson 간섭계를 이용한 유리 및 결정 매질의 굴절률 측정
최희주,차명식,김병주,임환홍 한국물리학회 2006 새물리 Vol.53 No.6
We measured the refractive indices of fused silica and LiNbO$_3$ single crystal plates by using Michelson interferometer. Although the conventional fringe-counting method can provide index values with relative ease, it generates large errors. We employed an improved fringe analysis method and, as a result, obtained a refractive index value of 1.457 for the fused silica substrate and an the ordinary index value of 2.286 for the LiNbO$_3$ crystal, with an uncertainty in of 10$^{-3}$ or below. This method can be utilized in establishing accurate Sellmeier's equations for solid optical media. 마이켈슨 (Michelson) 간섭계를 이용하여 용융석영유리와 LiNbO$_3$ 단결정 평판형 시료의 굴절률을 측정하였다. 이 방법을 사용하면 고체 매질의 굴절률을 비교적 손쉽게 측정할 수 있으나, 일반적으로 간섭무늬의 개수를 세는 방법은 매우 큰 오차를 보이므로 우리는 Michelson 간섭계를 이용하되 굴절률 측정의 정확도를 높일 수 있는 방법을 모색해보았다. 개량된 방법으로 용융석영유리의 굴절률은 1.457, LiNbO$_3$ 결정의 정상광 굴절률은 2.286로 측정하여 굴절률 측정값의 불확실성을 10$^{-3}$ 이하로 줄일 수 있었다. 이 방법은 고체 광학 매질의 굴절률 분산식 수립에 쉽게 적용될 수 있을 것으로 기대된다.
π-중심을 가진 유기 색소 분자의 비선형 흡수 과정 연구
최혜영,차명식,양현관,이광섭,이광희 한국물리학회 2004 새물리 Vol.48 No.1
We investigated nonlinear absorption processes in organic chromophores with thiophene and uorene À-centers. Laser pulses with durations of 7 ns and 35 ps were used to measure and compare the nonlinear absorption processes. Based on a ve level model for the molecules, we observed a much larger nonlinear absorption for the 7 ns pulse, which could be interpreted as being due to a two-photon absorption followed by an excited state absorption, We verifed that the strength of the nonlinear absorption increased not only with the two-photon absorption coecient but also with the lifetime of the excited state.
여러 회절광의 세기를 비슷하게 분배하는 회절격자의 제작
홍동리,차명식 한국물리학회 2007 새물리 Vol.54 No.3
A balanced or equal beam splitter is necessary in several optical experiments, such as complicated multi-beam pump-probe spectroscopy. We fabricated photoresist surface-relief gratings with different duty cycles in order to achieve relatively balanced intensities among the diffraction orders. A grating with a duty cycle of 1:3 gave relatively balanced beam splitting among the $\pm$0, $\pm$1, and $\pm$2 orders without significantly sacrificing the total diffraction efficiency. 한 개의 빔을 여러 개의 균일한 빔으로 나누는 beam 분배기는 복잡한 multi-beam pump-probe 분광학 실험 등의 광학 실험에 필요하다. 우리는 회절 차수들의 세기가 상대적으로 균일하게 나오게 하기 위해서 각각 다른 duty비로 photoresist 표면 위상 회절격자를 만들었다. Duty비 1:3의 회절격자는 전체 회절효율에 있어서 큰 손실 없이 $\pm$0, $\pm$1, $\pm$2차 회절광들의 세기를 비교적 균일하게 분배했다.