• Journal of electromagnetic engineering and science
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• v.15 no.4
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• pp.206-212
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• 2015

This paper introduces new wideband antenna-filter-antenna (AFA) uniform arrays that can be utilized as frequency selective surfaces (FSS) with low loss and sharp roll-off response, which are highly desirable characteristics for millimeter wave applications. The design adopts a simple 3-layer single polarization structure consisting of two patch antennas and a resonator. Both simulations and measurements are used to characterize the performances of the proposed design. Overall results show 18.5% 10-dB bandwidth. For the targeted band the insertion loss is less than 0.2 dB. Possible applications include quasi-optical amps, grid mixers and radomes for aircraft radar antennas.

• Korean Journal of Optics and Photonics
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• v.10 no.6
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• pp.507-511
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• 1999

A 10 GHz timing extracted signal which is phase-locked to a 10 Gbit/s mode-locked optical fiber laser pulse train is obtained using a tour-wave-mixing signal in semiconductor optical amplifier. The phase-locked loop wm, demonstrated ~Llccessful1y over 8 hours and found to have the lock-in frequency range of 30 KHz. 0 KHz.

• Korean Journal of Optics and Photonics
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• v.5 no.4
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• pp.439-444
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• 1994

When diffraction by arbitrary two-dimensional surface-relief dielectric gratings is analyzed using the rigorous three-dimensional vector coupled-wave analysis, it is found that the matrix eigenvalue problem pertaining to the analysis can always be simplified to that for a matrix which has the dimension of a quarter of the original, so that computing time and memory requirements for computer may be greatly reduced. However this kind of simplification can not be obtained in the case of volume diffraction gratings. tings.

• Korean Journal of Optics and Photonics
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• v.7 no.1
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• pp.77-86
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• 1996

We employ the SOR method to analyze CPW electrodes of Ti:$LiNbO_3$ Mach-Zehnder traveling-wave optical modulator in the tapered region of an optical modulator. In the tapered region of the modulator, we design the electrodes satisfying $Z_c=50{\Omega}$. In the modulation region, we find two find sets of design parameters. One set is for $Z_c=50{\Omega}$, $n_{eff}=2.26$ and the another is for $n_{eff}=2.2$, $Z_c=47.7{\Omega}$.

• Current Optics and Photonics
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• v.1 no.2
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• pp.138-142
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• 2017

Terahertz (THz) generation by periodically-poled $KTiOPO_4$ (PPKTP) with a quasi-phase-matching scheme based on cascaded difference frequency generation (DFG) processes is theoretically analyzed. The cascaded Stokes interaction processes and the cascaded anti-Stokes interaction processes are investigated from coupled wave equations. THz intensities and quantum conversion efficiency are calculated. Compared with non-cascaded DFG processes, THz intensities from 10-order cascaded DFG processes are increased to 5.53. The quantum conversion efficiency of 479.4% in cascaded processes, which exceeds the Manley-Rowe limit, can be realized.

• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.482-485
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• 1997

A new laser Doppler velocimeter employing a $CO_2$laser has been developed by using its optogalvanic effect. A change in the electric impedance of a discharge, induced by mixing of a returned wave with an originally existing wave inside the cavity, was employed to detect the Doppler frequency shift. A Doppler frequency shift as much as 60 KHz was detected, and also a good linear relationship between the velocity and the Doppler frequency shift was obtained.

• Current Optics and Photonics
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• v.2 no.3
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• pp.215-220
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• 2018

A novel porous-core hexagonal lattice photonic crystal fiber (PCF) is designed and analyzed for efficient terahertz (THz) wave propagation. The finite element method based Comsol v4.2 software is used for numerical analysis of the proposed fiber. A perfectly matched layer boundary condition is used to characterize the guiding properties. Rectangular air-holes are used inside the core to introduce asymmetry for attaining high birefringence. By intentionally rotating the rectangular air holes of porous core structure, an ultrahigh birefringence of 0.045 and low effective material loss of $0.086cm^{-1}$ can be obtained at the operating frequency of 0.85 THz. Moreover, single-mode properties, power fraction in air core and confinement loss of the proposed PCF are also analyzed. This is expected to be useful for wideband imaging and telecom applications.

• Korean Journal of Optics and Photonics
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• v.16 no.2
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• pp.138-142
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• 2005

In this paper, a method to eliminate the polarization dependent properties of fiber-to-planar waveguide couplers using a thin half-waveplate is proposed and demonstrated. The operation principle of the device is explained and the fabrication technology is presented. It is experimentally shown that the resonance wavelengths of the device are independent of the polarization state of input light.

• Korean Journal of Optics and Photonics
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• v.12 no.6
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• pp.437-445
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• 2001

We examine theoretically the properties of the force on Mie particles induced by evanescent fields at a system of multilayer films (including a metal film), at which the surface plasmon resonance is excited by a p-polarized plane electromagnetic wave. An expression of the surface plasmon-coupled evanescent fields produced in Kretschmann (or Sarid) geometry is expanded in terms of vector spherical wave functions, while multiple reflections between the Mie particle and the metal boundary are taken into account. The Cartesian components of the force on Mie particles by the evanescent fields are analytically formulated and numerically evaluated. The force components are increased by one or two orders of magnitude at metal boundaries over those at dielectric boundaries. As a result, we can confirm the possibility of stable manipulation or rotation of a finite-sized object by forces of surface plasmon-coupled evanescent fields.

• Korean Journal of Optics and Photonics
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• v.2 no.2
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• pp.74-82
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• 1991

This study is to investigate the distribution of the radiation force exerted on a homogeneous sphere by two circularly-polarized counterpropagating $TEM_{00}$ laser beams. The time-averaged expressions of the rediation force are derived for both cases of two interfering $TEM_{00}$ laser beams and a standing plane electromagnetic wave. The radiation force is numerically calculated and the physical interpretations of computed results are presented. The results in this paper will be useful in the optical levitation experiment using two counterpropagating $TEM_{00}$ laser beams or a standing plane electomagnetic wave.