• Journal of the Optical Society of Korea
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• v.6 no.3
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• pp.108-116
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• 2002

Lasing modes of laser-diode-pumped fiber grating lasers are analyzed by coupled-mode theory. First, a power series solution of the coupled-mode equations is derived under the assumption of an exponentially-decreasing longitudinal modal gain profile for a laser-diode-pumped grating section, followed by determination of the transfer matrix for such a section. Based on these results, an eigenvalue equation for oscillation is then derived and solved numerically for the lasing modes of uniform and phase-shifted fiber grating lasers. Comparisons made with the uniform-gain results indicate that, surprisingly, the lasing mode characteristics are not as significantly altered as might be expected in most cases, even for a highly nonuniform gain profile. In the case of a phase-shifted grating, the phase-shift position appears to have a much greater impact on determining the threshold gain, the modal field distribution, and the front-to-back output power ratio.

• Journal of the Korean Institute of Navigation
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• v.25 no.2
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• pp.131-136
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• 2001

A new analysis method of lumped-element directional coupler for CATV was proposed, where the even-and odd-mode theory for a symmetrical coupled-line directional coupler was applied to a transformer-type directional coupler. In addition, the tap-offs were analyzed by the proposed theory, which are widely used in CATV (Cable Television) systems. By comparing the calculated results for S-parameters results to the measured ones using only the even-and odd-mode reflection coefficients, the validity of the proposed analysis method was confirmed. Then, it was clearly shown that the tap-off has very wide bandwidth from 5 MHz to 4,000 MHz by adopting the proposed theory.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.3
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• pp.346-351
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• 2001

A new analysis method was proposed, where the even . odd-mode theory for a symmetrical coupled-line directional coupler was applied to a transformer-type directional coupler. In addition, the tap-offs were analyzed by the proposed theory, which are widely used in CATV (Cable Television), DBS (Direct Broad- casting Satellite), CS (Communication Satellite) systems. By comparing the calculation results to the measured ones using the even . odd-mode reflection coefficients only, the validity of the proposed analysis method was confirmed. Then, the tap-off has been broadened from 5 MHz over 4,000 MHz by adopting the proposed theory.

• Steel and Composite Structures
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• v.38 no.4
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• pp.355-363
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• 2021

The present paper attempts to investigate the propagation of plane waves in an isotropic elastic medium under the effect of initial stress and temperature-dependent properties. The modulus of elasticity is taken as a linear function of the reference temperature. The formulation is applied under the thermoelasticity theory with dual-phase-lag; the normal mode analysis is used to obtain the expressions for the displacement components, the temperature, the stress, and the strain components. Numerical results for the field quantities are given in the physical domain and illustrated graphically. Comparisons are made with the results predicted by different theories (Lord-Shulman theory, the classical coupled theory of thermoelasticity and the dual-phase-lag model) in the absence and presence of the initial stress as well as the case where the modulus of elasticity is independent of temperature.

• Structural Engineering and Mechanics
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• v.56 no.4
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• pp.649-665
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• 2015

The present paper attempts to investigate the propagation of plane waves in generalized piezo-thermoelastic medium under the effect of rotation. The normal mode analysis is used to obtain the expressions for the displacement components, the temperature, the stress and the strain components. Comparisons are made with the results predicted by different theories (Coupled theory, Lord-Schulman, Green-Lindsay) in the absence and presence of rotation.

• Journal of the Optical Society of Korea
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• v.1 no.2
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• pp.94-99
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• 1997

In this paper, we calculate the four coefficients for the quantum theory of multiwave mixing including a local-field correction resulting from dipole-dipole interactions. We make contact with the semiclassical calculations of probe absorption and four-wave-mixing coupling coefficients, and illustrate the effects of local field corrections on resonance-fluorescence and coupled-mode-fluorescence spectra. The method uses the hybrid quantum-Langevin-equation master-equation approach of An and Sargent.

• Journal of the Optical Society of Korea
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• v.1 no.2
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• pp.67-73
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• 1997

Light wave diffraction from multiple superposed volume gratings is inestigated using a perturbative iteration method of the integral equation of Maxwell's wave equation. The host material and index gratings are anisotropic and non-coplanar multiple volume gratings are considered. In this method, the paraxial approximation and lack of backward scattering in conventional coupled mode theory are not assumed. Systematic analysis of anisotropic wave diffraction due to multiple noncoplanar volume index gratings is performed in increasing level of diffraction orders corresponding to successive iterations.

• Journal of electromagnetic engineering and science
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• v.13 no.1
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• pp.38-43
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• 2013

We derive the Z-parameters for the two coupled antennas used for wireless power transfer under the assumption that the antennas are canonical minimum scattering antennas. Using the Z-parameter and the maximum power transfer efficiency formula, we determine the maximum power transfer efficiency of wireless power transfer systems. The results showed that the maximum power transfer efficiency increases as the mode number or the radiation efficiency increases. To verify the theory, we fabricate and measure two different power transfer systems: one comprises two antennas generating $TM_{01}$ mode; the other comprises two antennas generating $TM_{02}$ mode. When the distance between the centers of the antennas was 30 cm, the maximum power transfer efficiency of the antennas generating the $TM_{02}$ mode increased by 62 % compared to that of the antennas generating the $TM_{01}$ mode.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.10
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• pp.53-59
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• 1997

In this paper, we present a 20 GHz low-loss dual-mode channel filter designed by using mode matching method. The performance of dual-mode channel filter mainly depends on iris characteristics. Therefore the exact design of iris is the key point to get good frequncy response of the filter. MOde matching technique is widely used ot design several kinds of waveguide filters because it is simple in theory and can easily calculate the scattering matrices at the discontinuities with simple structure like iris coupled filters. Additionally the effect for finite thickness of the iris in the dual-mode cavity iflter is analyzed by te full-wave method, providing the exact filter implementation without trial and error.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.225-232
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• 2014

Optical parametric amplification has been analyzed for the Cerenkov-idler configuration in planar waveguides. The coupled-mode theory is employed for the analysis. The coupled-mode equations are derived and the approximate analytic solution is obtained for no pump depletion. From the analytic solution, it is shown that the signal power gain can be enhanced as the Cerenkov radiation angle of the idler approaches to zero. The numerical example is also shown for the effect of the Cerenkov radiation angle approaching zero.