• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.4
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• pp.645-650
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• 2019

In this paper, a specifically designed waveguide structure that can carry first, and second-order orbital angular momentum(: OAM) mode is proposed. The proposed optical waveguide consists of three Si stripes embedded in $SiO_2$, which is suitable for implementing on-chip integration and fabrication by standard thin film deposition and etching processes. The second-order OAM mode was generated by combining two eigenmodes, which are calculated by finite difference method(: FDM). The topological charge number of the first, and second-order OAM mode was calculated as l=0.9642 and 1.8766 respectively, which is close to the theoretical value.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.2
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• pp.353-359
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• 2006

As for the characteristic of elements for a lot of communication used in light communication systems, it is affected according to structure of directional coupler. We carried out study on a characteristic of the directional coupler which had waveguide structure to have perturbation phenomenon in this paper and ran simulation on the characteristic that we changed structure of directional coupler too, and was got. Confirmation was able to do that it operated with an optical filter, and the directional coupler which added waveguide structure to produce perturbation phenomenon by the results was able to confirm what we adjusted duty ratio of waveguide structure too, and operated with a more excellent optical filter. Through simulation, the case that duty ratio changed than the case that duty ratio of waveguide structure was $50\%$ was able to get an excellent answer characteristic of a -l8dB degree.

• Journal of the Korean Chemical Society
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• v.49 no.1
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• pp.47-55
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• 2005

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.10
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• pp.1855-1861
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• 2017

In this paper, the gain enhancement of an SDPA using a director and two parasitic patches is studied. The modified balun is used to increase the bandwidth, whereas the director and two parasitic patches are appended to the SDPA to enhance the gain in the middle and high frequency bands. The effects of the distance between the director and parasitic patches on the antenna performance are analyzed, and the SDPA with a gain over 7 dBi at 1.54-2.99 GHz band is designed. The proposed SDPA is fabricated on an FR4 substrate with a dimension of $90mm(L){\times}135mm(W)$ in order to validate its performance. The fabricated antenna shows a frequency band of 1.56-3.10 GHz for a VSWR < 2, and it is confirmed by measurement that gain maintains over 7 dBi in the frequency range of 1.54-3.00 GHz.

• Korean Journal of Optics and Photonics
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• v.17 no.1
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• pp.99-103
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• 2006

A tunable wavelength filter was proposed and demonstrated by using the UV nanoimprint technique. It consists of a Bragg grating in polymer waveguides and a heating electrode. The manufacturing of the grating was substantially simplified with the introduction of a smart imprint stamp containing a waveguide pattern integrated with the grating pattern. The center wavelength of the filter was successfully tuned by taking advantage of the thermooptic effect in polymers, which was induced by supplying electrical power to the electrode. For the fabricated device, a transmission dip of ${\~}$15 dB and a 3-dB bandwidth of 0.8 nm were obtained at the Bragg wavelength of ${\~}$l560 nm. The achieved thermooptic tuning efficiency was ${\~}$0.28 nm/mW, while the center wavelength was shifted from 1560 nm to 1558 nm with the electrical power consumption of 7 mW.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.1
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• pp.58-66
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• 2002

Acousto-optical wavelength tunable optical filters in LiNbO$_3$ have been demonstrated using taperd directional weighted coupling acoustic waveguides and Ti double diffusion technique. Conversion efficiency in excess of 61%, 86% and sidelobe intensity of -14.29㏈, -14.99㏈ were measured at a wavelength of 1551.1nm RF frequency of 173.58MHz and RF power of 35㎽ for both TE and TM input polarizations, respectivelv. A spectral width of ~l.8nm and linear tuning late of 8.6nm/MHz were demonstrated. A 2.82$mutextrm{s}$ switching time has been measured. With two channels with 2.5nmseparation, channel cross-talk was lower than -l4㏈ for single wavelength filtering due to sidelobe.

• Korean Journal of Optics and Photonics
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• v.14 no.2
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• pp.142-145
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• 2003

The nonreciprocal phase shift characteristics of infinite slab optical waveguides with magneto-optic materials in the cladding layer was calculated at 1.55 ${\mu}{\textrm}{m}$ for optical isolators. The infinite slab waveguide structures considered in this paper were as follows. rho magneto-optic materials used as a cladding layer were Ce:YIG and LNB(LuNdBi)$_3$(FeAl)$_{5}$)$_{12}$,). Their specific Faraday rotations Θ$_{F}$ are 4500$^{\circ}$/cm, 500$^{\circ}$/cm at wavelength 1.55 ${\mu}{\textrm}{m}$ respectively. The guiding layer with multi-quantum well structure was used, and it consists of 1.3Q and InGaAs. In order to investigate the effect of evanescent field penetrating the cadding, layer, guiding mode characteristics were calculated for the cases when the substrate is InP and air. We calculated the minimum lengths of 90$^{\circ}$ nonreciprocal phase shifters and their optimum guiding layer thicknesses in various optical waveguide structures.res.s.

• Journal of Power System Engineering
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• v.3 no.3
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• pp.14-21
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• 1999

The wave nature of heat conduction has been developed in situations involving extreme thermal gradients, very short times, or temperatures near absolute zero. Under the excitation of a periodic surface heating in a finite medium, the hyperbolic and parabolic heat conduction equations and the damped wave equations in heat flux are presented for comparative analysis by using the Green's function with the integral transform technique. The Kummer transformation is also utilized to accelerate the rate of convergence of these solutions. On the other hand, the temperature distributions are obtained through integration of the energy conservation law with respect to time. For hyperbolic heat conduction, the heat flux distribution does not exist throughout all the region in a finite medium within the range of very short times(${\xi}<{\eta}_l$). It is shown that due to the thermal relaxation time, the hyperbolic heat conduction equation has thermal wave characteristics as the damped wave equation has wave nature.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.4
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• pp.659-664
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• 2020

In this paper, we propose a silicon-based electro-optic (EO) modulator which can modulate a sign of a topological charge number l of |l|=1 orbital angular momentum (OAM) mode. The proposed EO modulator consists of position-dependent doped Si waveguide core and undoped SiO2, cladding, which enables control of the effective index and propagation loss of two OAM constitutive eigenmodes. The modulator functions as OAM mode maintaining waveguide at -0.33V and as topological charge sign inverter at 10V. The output OAM mode purity is calculated through electric field distribution, showing high purity of |l|>0.92 in both cases.

• Korean Journal of Optics and Photonics
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• v.19 no.2
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• pp.127-131
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• 2008

A refractometric glucose biosensor incorporating a vertically coupled microring resonator in polymers was proposed and realized. The ring was covered with a target analyte of glucose solution with a certain concentration, so that its effective refractive index could be altered and, as a result, the resonance wavelength of the sensor was shifted. Therefore the concentration of the glucose solution can be estimated by observing the shift in the resonance wavelength. Two schemes were exploited for enhancing the sensitivity of the sensor. First, the effective refractive index of the polymeric waveguide used for the resonator sensor was adjusted to approach that of the target analyte as best as possible. Second, the ring waveguide, which serves as a crucial sensing part, was appropriately over-etched to enlarge its contact area with the analyte. The proposed resonator sensor was designed with the beam propagation method. The refractive indices of the core and cladding polymer involved were 1.430 and 1.375 respectively, leading to the waveguide's effective refractive index of ${\sim}1.390$, which is faiirly close to that of the glucose solution of ${\sim}1.333$. The prepared ring resonator with the $400-{\mu}m$ radius exhibited the free spectral range of 0.66 nm, the bandwidth of 0.15 nm, and the quality factor of 10,000. For the sensor operating at 1,550 nm wavelength, the achieved sensitivity was as great as 0.28 pm/(mg/dL), which is equivalent to 200 nm/RIU.