• The Journal of Korean Institute of Communications and Information Sciences
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• v.15 no.4
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• pp.278-285
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• 1990

It is well know that optical oupler that is composed of the polished single-mode optical fiber can separate two arbitrary wave lengths. Wavelength division ranges of the WDM optical coupler that is made of the bending fiber with radius R vary with the center wavelength of the signal and spacing between two cores. In this paper, when optical fiber is fixed with the radius R, We proposed the spacing between two cores that can provide minimum division range. Also, We proposed the minimum radius R necessary to separate two arbitary wavelengths of the signal.

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.192-193
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• 2002

지금까지 측면이 코어 가까이 연마된 잔일모드 광섬유와 평면 도파로 사이의 광결합을 이용한 소자들이 많이 연구되고 있다. 이를 이용한 소자들로는 광필터, 광변조기, 광스위치, 굴절계, 편광기 등이 있으며 최근에는 파장분할다중화(WDM)에서 인접채널간의 채널분리를 위한 소자로서 빗살필터의 연구 또한 활발히 이루어지고 있다. 이에 본 논문에서는 측면이 코어 가까이 연마된 단일모드 광섬유와 평면도파로 사이의 광결합을 이용한 빗살필터를 제작하였으며 열광학 효과를 이용하여 파장 가변 빗살 필터를 구현해 보았다. (중략)

• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.1
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• pp.81-90
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• 2007

The purpose of this study was to assess the effect of light-tip distance on the shear bond strength of a visible light-cured glass ionomer cement(Fuji Ortho LC ; GC, Japan) cured with three different light curing units : a halogen light(Elipar Trilight ; 3M ESPE, Seefeld, Germany), a Light Emitting Diode (LED, Elipar Freelight2 ; 3M ESPE, Seefeld, Germany) and a plasma arc light (Flipo ; LOKKI, France). 1. When used at a distance of 0mm from the bracket, the three light curing units showed no statistically different shear bond strengths. At distance of 3 and 6mm, no significant differences were found between the halogen and plasma arc lights, but both had significantly higher shear bond strengths than the LED light. 2. The halogen light and plasma arc light showed that no significant differences in bond strength were found among the three distances. Using the LED light, a greater light-tip distance produced significantly lower shear bond strengths.

• The korean journal of orthodontics
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• v.34 no.5 s.106
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• pp.429-438
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• 2004

The purpose of this study was to compare the effects of different light direction exposure times and setting times when using plasma arc light on shear bond strength of metal brackets. 240 extracted human premolars were randomly assigned to one of 16 groups Standardized brackets were bonded to enamel using different light curing units (Plasma arc light and Halogen light), exposure times (Plasma arc light 2. 4, 6 seconds and Halogen light 20 seconds). and light directions [Vertical direction [V] and Oblique direction [O]). 8 groups were tested after 5 minutes and the remaining 8 groups after 24 hours. The metal brackets were bonded with Transbond XT. Shear bond strength was measured by a universal testing machine. The results were as fellows: There were as differences between the shear bond strengths of the Vertical groups (V) and Oblique groups (O). regardless of exposure times and types of light curing units (p>0.05). The shear bond strength of the group with 2 seconds of plasma light were significantly lower than other exposure time groups (P<0.05). The shear bond strength tested after 5 minutes was lower than after 24 hours (p<0.05) The Adhesive Remment Index (ARI) score showed no statistically significant difference among the different groups. The results of this study suggested that the light direction of plasma arc light had no influence on the shear bond strength of metal brackets to enamel. and exposure times more than 4 seconds produced shear bond strengths similar to those Produced with a conventional halogen curing light.

• Korean Journal of Optics and Photonics
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• v.15 no.1
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• pp.28-33
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• 2004

An in-line fiber coupler, based on side-polished single-mode fibers covered with an intermediate coupling layer and a planar waveguide, is analyzed by modeling the interaction region as an equivalent multi-layered planar waveguide. The reflectance for the multi-layered structure with and without buffer layer is illustrated as a function of the refractive index and thickness of the overlay waveguides. When the refractive index of the overlay waveguides is greater than that of the fiber core, the conditions for the intermediate coupling layer to increase the power coupling from the fiber to the overlays is also explained. Through the experimental results using a LiNbO$_3$planar waveguide, we show that the theoretical analysis is reasonable and in good agreement with the measured values.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.37 no.5
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• pp.39-48
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• 2000

We newly proposed a polymer based vertical asymmetric optical coupler, which was characterized by simple fabricating procedure and short coupling length. And we fabricated a thermo-optic modulator using the polymeric optical coupler. We optimized the proposed device by coupling characteristic analysis. In a TE polarized 1.33${\mu}{\textrm}{m}$ wavelength, we obtained very short coupling length(L=277.6${\mu}{\textrm}{m}$) with 0.4${\mu}{\textrm}{m}$ thickness of middle layer, high coupling efficiency(94%), and asymmetric vertical waveguides with n$_{u}$ = 1.522, n$_{l}$ = 1.51. We implemented vortical asymmetric thermo-optic modulator with lower inverted rib waveguide and upper slab waveguide. In the 600Hz bandwidth and 4.5㎽ input power, the extinction ratio of the mode was 17㏈ with an insertion loss of 4.5㏈.

• Korean Journal of Optics and Photonics
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• v.10 no.2
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• pp.120-127
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• 1999

We discussed two main types-conformal and non-conformal (powered) - of holographic combiner. A theoretical model based on the Kogelnik's coupled wave theory was used to illustrate bandwidth and efficiency properties. Also we showed numerical values for the aberrations that are induced by a wavelength shift from construction to reconstruction and found optimum coordinates to reduce the chrolatic aberation of construction beams using aberration balancing techniques. The holographic combiner manufactured in conformal type with 60$^{\circ}$ incidence angle at 514.5 nm had narrow angular bandwidth (FWHM) of 4.1" and spectral bandwidth of 11.4 nm, while non-conformal one with 50$^{\circ}$, 30$^{\circ}$ incidence angle at 514.5 nm showed spectral and angular bandwidth of 10.7 nm and 5.5$^{\circ}$, respectively.vely.

• Journal of IKEEE
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• v.3 no.1 s.4
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• pp.86-92
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• 1999

A rigorous modal transmission-line theory (MTLT) based on effective dielectric method (EDM) is introduced and developed for the design of optical directional couplers with rib-type. This approach provides a rigorous numerical algorithm that takes all the possible guided components into consideration, and thus may serve as an appropriate reference to access the accuracy of such simplified methods as effective index method (EIM) and perturbation theory. Consequently, to search the optical parameters for maximum power coupling of the optical couplers, we evaluate the operating wavelength, the interval S between rib guides and the thickness t of a cladding layer.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.174-175
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• 2003

광섬유-평면도파로 결합기는 평면도파로의 재료와 구조에 따라 다양한 응응이 가능하다. 특히 평면도파로의 전기광학 효과를 이용하면 고속 광변조 현상을 얻을 수 있다. 평면도파롱에 전기장을 인가하기 위해서는 두개의 도체 전극이 필요하다. 전극으로 주로 금속을 많이 이용하기 때문에 금속층이 포함된 광섬유-평면도파로 결합기의 특성을 연구하는 것이 요구된다. 본 논문에서 그림 1과 같이 금속 중간층이 포함된 광섬유-평면도파로 결합기의 구조의 동작특성을 측정하고 결과를 보고한다. (중략)

• Korean Journal of Optics and Photonics
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• v.33 no.4
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• pp.137-145
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• 2022

A directional coupler device, one of the fundamental components of photonic integrated circuits, distributes optical power by evanescent field coupling between two adjacent optical waveguides. In this paper, the design process for manufacturing a directional coupler device is reviewed, and the accuracy of the design results, as seen from the characteristics of the actual fabricated device, is confirmed. When designing a directional coupler device through a two-dimensional (2D) beam-propagation-method (BPM) simulation, an optical structure is converted to a two-dimensional planar structure through the effective index method. After fabricating the directional coupler device array, the characteristics are measured. To supplement the 2D-BPM results that are different from the experimental results, a 3D-BPM simulation is performed. Although 3D-BPM simulation requires more computational resources, the simulation result is closer to the experimental results. Furthermore, the waveguide core refractive index used in 3D-BPM is adjusted to produce a simulation result consistent with the experimental results. The proposed design procedure enables accurate design of directional coupler devices, predicting the experimental results based on 3D-BPM.