• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.30-31
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• 2002

하나의 구동기를 작동하여 거울을 변형시킬 때, 변형된 거울면의 형태를 영향 함수(influence function)라고 정의하며, 이러한 영향 함수를 이용하여 적응 광학계의 주요한 광학 요소인 변형 거울을 효과적으로 모형화하고 설계할 수 있다. 본 논문에서는 유한요소해석을 이용하여 계산된 변형 거울의 실제 영향 함수를 가우시안 함수(Gaussian function) 형태로 단순화하고, 추가로 구동기들 사이의 영향을 고려한 커플링 계수(coupling coefficient)를 도입하여, 주어진 구동기 배열에 대한 영향 함수를 결정하였다. (중략)

• Korean Journal of Optics and Photonics
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• v.13 no.5
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• pp.400-407
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• 2002

Two dimensional solitary waves are stably propagated in a saturable medium which has a saturable nonlinear index as input intensity. However, in the case of low intensity. a negative fifth-order nonlinear medium has properties of a saturable medium. So a Gaussian beam travels stably. The propagation process into the fifth order nonlinear medium of the Gaussian beam with a weak intensity is investigated by using the computer simulation of the two-dimensional nonlinear Schrodinger equation. As a result, it is confirmed that the two-dimensional spatial solitary waves are stably propagated in this medium when the incident powers are self-trapping powers. In the condition of the phase difference and collisional angle between two input beams of 180 degree and 0.05 degree, respectively, we can confirm that all optical switching is as simple as controlling the incident power of one input beam.

• Korean Journal of Optics and Photonics
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• v.7 no.3
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• pp.196-199
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• 1996

The amplitude LSF(Line spread function, $C_1e^{{o^2}{x^2}}$ or amplitude impulse) of the Gaussian apodized annular pupil is found to be same to that of the full aperture LSF($C_0e^{{o^2}{x^2}}$). $C_0$ and $C_1$ depending on $\sigma$, ${\omega}_0=\frac{2{\pi}}{\lambda}\;\frac{a_0}{l}$ and ${\omega}_0'=\frac{2{\pi}}{\lambda}\;\frac{a_0'}{l}$ which are the geometric parameter and pupil coordinates of the annular pupil. The important inequality relation among ${\omega}_0,\;{\omega}_0'$, a (fraction of diffraction amplitude) and $\sigma$ is obtained. It is $\frac{{\omega}_0}{\sqrt{2}}<{\sigma}{\le}(\frac{1-a}{2a})^{1/2}\;{\omega}_0$, and in the case of $a=e^{-1},\;a_0'{\le}0.34a_0$. The case of λ=0.013${\mu}{\textrm}{m}$, l=20 cm, $a_0=5cm$ and $a_0=0.34a_0=1.7cm$ give a Gaussian apodized superresolution ${\Delta}=\frac{\sqrt{log2}}{\sigma}=0.008{\mu}m$ annular pupil with the intensity signal equal to $e_{-2}$ times the signal obtainable by using the full aperture system(a=1)

• Korean Journal of Optics and Photonics
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• v.7 no.4
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• pp.434-439
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• 1996

To investigate influence of the incident beams which have the truncated Gaussian amplitude and of the shapes of bump on read-out signal is an optical disc, and the point spread function on bump, the scalar diffraction theory is used in this paper. We consider the truncated Gaussian amplitudes which are $\sigma$=0, 0.5, 1.5, and 2.5, the height of bump which is given by $n{\Delta}_0={\lambda}/4$, and the phase height of bump which is then given by ${\Phi}_0={\pi}$. We also consider the shapes of the bump which are a rectangular shape, a frustoconical shape, and a conical shape. It is shown that as the truncation of incident beam reduces the radius of central spot on bump decreases, the maximum value of read-out signal increases, and that the size of bump decreases. From these results, we get better read-out signal and the reduced cross-talk in optical disc when the truncation of incident beam reduces. Therefore a laser beam having less truncated Gaussian amplitude may useful for an actual optical disc.

• Journal of Korean Ophthalmic Optics Society
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• v.9 no.2
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• pp.291-299
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• 2004

DLC films were deposited using the ECR-PECVD method with the fixed deposition condition, such as ECR power, methane and hydrogen gas-flow rates and deposition time, for various substrate bias voltage. We have investigated the ion bombardment effect induced by the substrate bias voltage on films during the deposition of film. The characteristic of the films were analyzed using the FTIR, Raman, and UV/Vis spectroscopy analysis shows that the amount of dehydrogenation in films was increased with the increase of substrate bias voltage and films thickness was decreased. Raman scattering analysis shows that integrated intensity ratio(ID/IG) of the D and G peak was increased as the substrate bias voltage increased and films hardness was increased. Optical transmittances of DLC film were decreased with increasing deposition time and substrate bias voltage. From these results, it can be concluded that films deposited at this experimental have the enhanced characteristics of DLC because of the ion bombardment effect on films during the deposition of film.

• Korean Journal of Optics and Photonics
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• v.15 no.3
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• pp.214-221
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• 2004

We theoretically and experimentally investigate the effect of apodization on the transmission characteristics of linearly chirped fiber Bragg gratings(CFBGs). Based on the UV beam scanning method along a phase mask, we fabricated several apodized CFBGs with different apodization profiles such as Gaussian, Raised-cosine, Blackman, and Hyperbolic tangent. During the UV beam scanning, the phase mask is dithered by a PZT(Piezoelectric transducer) which is precisely controlled by a computer program so that the apodization profiles can be flexibly applied to the grating. We measured the reflection spectra and group delay characteristics of CFBGs with the different apodization profiles, and compared them according to their properties such as reflectivity, sidelobes, and group delay ripple (GDR). The peak-to-peak of GDR could be suppressed to less than 20 ps.

• Korean Journal of Optics and Photonics
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• v.14 no.1
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• pp.51-57
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• 2003

The hologram of an object contains the information of the object's depth distribution as well as the depth location of the object. However these pieces of information are blended together as a form of fringe pattern. This makes it hard to extract the depth location of the object directly from the hologram. In this paper, I propose a numerical method which separates the depth location information from the single-sideband hologram by gaussian low-pass filtering. The depth location of the object is extracted by numerical analysis of the filtered hologram. The hologram at the object's depth location is recovered by the extracted depth location.

• Korean Journal of Optics and Photonics
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• v.9 no.5
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• pp.342-347
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• 1998

We present a theoretical analysis of Gaussian beam propagation in nonlinear Kerr media by using aberration-free approximation and Huygens-Fresnel diffraction integral and obtain a simple analytic formular for Z-scan characteristics. Z-scan experiments are carried out on amorphous $As_2S_3$ thin film and compared with the theory developed, showing good agreement. The sign and the value of ${\gamma}$ have been measured at 633 nm to be $+8.65{\times}10^{-6}\textrm{cm}^2/W$. We also measured the far-field intensity profiles, which confirm again self-focusing effect.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.243-251
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• 1993

We have derived Gaussian bracket expressions of aplanatic and achromatic conditions and obtained the numerical solutions for each of two modules of the telephoto type telescope objective free from the Seidel first order spherical aberration, coma, and longitudinal chromatic aberration. The system which is for use in sighting a target is optimized within the resolution of eyes. The objective lens satisfying the aplanatic and achromatic condition has f/8.5 with the half field angle 0.$3^{\circ}$, and the telephoto ratio is 0.839 with the focal length of 30 cm.

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.305-312
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• 2012

We numerically demonstrate the performance of a plasmonic lens composed of an array of nanoslits perforated on thin metallic film with slanted cuts on the output surface. Embedding Kerr nonlinear material in nanoslits is employed to modulate the output beam. A two dimensional nonlinear-dispersive finite-difference time-domain (2D N-D-FDTD) method is utilized. The performance parameters of the proposed lens such as focal length, full-width half-maximum, depth of focus and the efficiency of focusing are investigated. The structure is illuminated by a TM-polarized plane wave and a Gaussian beam. The effect of the beam waist of the Gaussian beam and the incident light intensity on the focusing effect is explored. An exact formula is proposed to derive electric field E from electric flux density D in a Kerr-Dispersive medium. Surface plasmon (SPs) modes and Fabry-Perot (F-P) resonances are used to explain the physical origin of the light focusing phenomenon. Focused ion beam milling can be implemented to fabricate the proposed lens. It can find valuable potential applications in integrated optics and for tuning purposes.