• Korean Journal of Optics and Photonics
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• v.14 no.4
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• pp.359-364
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• 2003

We propose a novel vertical directional coupler with polarization independent very short coupling lengths using the double-sided deep-ridge waveguide structure which could be implemented using double-sided process to polarization insensitive deep-ridge waveguide structures and investigate the effect of various structure parameters on the coupling length. Variation of coupling length for the variation of the waveguide width is smaller than that for the variation of the core thickness. Coupling length decreases as the inner cladding layer thickness and the core thickness decrease. The waveguide width with the polarization independent coupling length decreases as the inner cladding layer thickness decreases for the same core thickness and the core thickness decreases for the same inner cladding layer thickness.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.293-298
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• 2004

We investigate the effect of the wing width and thickness of a Double-Sided Deep-Ridge(DSDR) vertical directional coupler on the coupling length dependent on the polarization, We have found that the DSDR vertical directional coupler without a wing does not have polarization independent coupling lengths. The variation of the coupling length of TE and TM modes and the difference between the coupling lengths of the two modes are negligible as the wing width increases beyond the specific wing width for the same wing thickness. Thus, we can see that a DSDR vertical directional coupler has a wing width larger than the minimum wing width to obtain the polarization independent coupling length. The minimum wing width increases as the wing thickness increases for the same core thickness and as the core thickness decreases for the same wing width. Also, we have found that the minimum wing thickness is determined by the core thickness and the minimum wing thickness decreases as the core thickness increases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.8
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• pp.1108-1116
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• 1993

Y-branch directional coupler optica1 switches with two different coupling lengths are fabricated on z-cut LiNbO3 and tested at r = 1.3 rm. The normal mode and coupled mode theories are utilized to calculate device coupling length and switching voltage. Simulation of the beam propagation method (BPM) is also performed to confirm the device coupling lengths. For dc operation, experimental results are in good agreement with the modee theories expectation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.13 no.2
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• pp.47-52
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• 2013

A novel architecture to reduce dramatically the coupling length of multimode interference-based couplers (MMICs) is proposed by replacing conventionally designed MMICs by cascaded two-section plasmonic stepped MMICs (PS-MMIC). For the 60% cross power splitting ratio in a stepped-width MMIC, the coupling length of device results in around 42% length reduction. Furthermore, the power splitting ratio and coupling length of plasmonic MMIC just vary around 1~2% along the variation of refractive index. On the contrast, those factors for the variation of MMIC's width strongly vary around 30~40%.

• The Journal of the Acoustical Society of Korea
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• v.34 no.5
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• pp.360-370
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• 2015

In case that an infinite length waveguide structure is connected with a finite length structure, it is required to combine a wave approach for the waveguide structure and a modal approach for the finite length structure to investigate the dynamic response of the connected target structure. In this study, the wavenumber finite element (WFE) analysis is adopted for the infinite length waveguide substructure and a finite element (FE) method is applied for the finite length substructure and then their results are coupled in terms of the impedance or mobility at the connected points between the substructures. As a structural model, an infinite length cylindrical shell with a rectangular plate inside is regarded. These two substructures are connected at the four corner points of the plate, rigidly or resiliently. From this investigation, it was confirmed that the wave approach (WFE method) and modal approach (FE method) can be combined by the impedance coupling.

• Korean Journal of Optics and Photonics
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• v.15 no.1
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• pp.12-16
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• 2004

We show that the extinction ratio is improved using slight asymmetry in two core refractive indices of polarization independent very short vertical directional couplers with the double-sided deep-ridge (DSDR) waveguide structure. The optimum asymmetry with the maximum extinction ratio and the tolerance of the refractive index of core with the extinction ratio larger 1ha]1 30 ㏈ increase as the thickness of inner cladding layer and the two cores decrease due to the increase of the coupling strength between the two cores. Also, the device length and the tolerance of the device length with the extinction ratio larger than 30 ㏈ decrease as the thickness of the inner cladding layer and the two cores decrease due to the increase of the coupling strength between the two cores. We show that polarization independent vertical directional couplers with the DSDR waveguide structure with the device length less than 100 ${\mu}{\textrm}{m}$ and the extinction ratio larger than 30 ㏈ could be implemented.

• Journal of the Korean Magnetics Society
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• v.19 no.2
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• pp.43-46
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• 2009

The magnetic and structural properties of the (8, 0) BN nanotubes with transition metals (TM) of Fe, Co, or Ni substitution for B or N were investigated using a first-principles calculation. It was found that TM substitution makes the cross section being distorted and the bond length TM-B or TM-N being longer than that of the original B-N one. The magnetic moment is larger for the TM substitution for B than one for N, and it is mainly due to the 3d electrons of TM atoms.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.1
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• pp.14-19
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• 2010

In this paper, a novel architecture for device miniaturization of multimode interference-based couplers (MMICs) is proposed by replacing conventionally designed MMICs by cascaded two-section stepped-width or stepped-index MMICs. For the 82% cross coupling efficiency in a stepped-width MMIC, the coupling length of device results in just 6.7% length reduction. However, for a stepped-width and stepped-index MMIC, the coupling efficiency increases to 93% and the length reduction of 9% occurs. Furthermore, with additional incorporation of tapered devices, it shows that a compact MMIC can be designed in which the coupling efficiency is 90% and the length is reduced to 25%.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.12
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• pp.1321-1328
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• 2003

In this paper, we demonstrate that the directivity of the CPW(Coplanar Waveguide) directional coupler with finite-extent backed conductor is enhanced by eliminating center region of backed conductor appropriately. If the backed conductor is removed at center region of couplers, the couplers have two backed conductors. If effective odd mode dielectric constant is decreased at center region, the electrical length for odd mode is changed and phase velocity is same at the directional couplers. Hence, directivity is improved. The eliminated length is solved by an odd and even mode analysis. The designed moderate CPW directional coupler with the proposed compensation structure has excellent directivity and matching characteristic at center frequency in simulation and measurement.

• Proceedings of the Optical Society of Korea Conference
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• 1991.06a
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• pp.22-22
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• 1991

광의 병렬처리 능력을 잘 활용한 1$\times$4 매트릭스 스위치의 구조와 전극구조를 설계하고 스위치 특성을 조사하기 위하여 beam propagation method(BPM)를 이용하여 수치계산을 하였다. 기존의 매트릭스 스위치는 대부분의 경우 방향성 결합기를 스위치 element로 이용하여 왔으나 이 결합기는 소자의 길이가 길기 때문에 단일 LinBO3 웨이퍼상에 집적할 수 있는 매트릭스 스위치의 크기가 제한되는 단점이 있다. 본 연구에서는 두 도파로 사이에 세 번째 도파로를 삽입하여 두 도파로를 결합시키는 세 도파로 결합기를 스위치 element로 사용하여 세 개의 스위치 element를 LiNbO3기판위에 직렬로 집적시킨 1$\times$4 매트릭스 스위치를 구성하였다. 스위치 element와 1$\times$4 매트릭스 스위치를 구성하였다. 스위치 element와 1$\times$4 매트릭스 스위치의 특성을 BPM을 사용하여 수치계산할 때 단일 모드 도파로의 유효 굴절을 분포는 n(X) = nm + $\Delta$ncosh-2(2x/w)의 형태로 가정했으며, 사용된 파라미터의 값은 각각 nm=2.1455, $\Delta$n=0.003, W=5$mu extrm{m}$, d=5$\mu\textrm{m}$, λ=1.3$\mu\textrm{m}$ 이고 S-파라메터의 값은 0.95927이므로 단일 모드 도파로가 된다. 계산결과 스위치 element의 결합길이는 3810$\mu\textrm{m}$이며 도파로의 길이가 결합길이와 같을 때 전극에 인가된 전압에 의한 도파로의 굴절을 섭등의 함수로 출력광의 세기를 계산한 결과 스위칭 전압은 14.85volt이고 crosstalk는 -18.9dB였다. 이 스위치 element로 구성된 1$\times$4 매트릭스 스위치는 스위칭 전압을 세 개의 전극에 적절한 조합으로 인가함으로써 한 입력 도파로에 결합된 광이 내개의 출력 도파로중 한 도파로에 스위칭 된다. 한편 수치계산의 결과를 실험적으로 확인하기 위해 스위치 element와 1$\times$4 매트릭스 스위치를 z-cut의 LinbO3 결정에 Ti을 열확산시켜 제작한 소자의 스위칭 특성을 발표할 예정이다.