• Journal of the Optical Society of Korea
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• v.7 no.3
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• pp.145-149
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• 2003

The anisotropy of electron energy distribution in oxygen plasmas produced by a high intensity laser was investigated by using polarization spectroscopy. An ultra-short pulsed laser with a pulse duration of 66.5 fs and a power density of $1 {\times} 10^17/ W/$\textrm{cm}^2$$ was used. At this power density and pulse duration, the plasma was generated predominantly by optical field ionization. The degree of polarization of OVI 1s$^2$2p$^2$p2- 1s$^2$4d$^2$D$^{0}$ (J = 1/2-3/2 and 3/2-5/2) transition line at 129.92 $\AA$ was measured. O VI 1s$^2$2p$^2$P$^2$ -1s$^2$4s$^2$S$^2$ (J = 1/2-1/2 and 3/2-1/2) transition line at 132.26 $\AA$ was used to calibrate the sensitivity of the optical system. The dependencies of the degree of polarization on the initial gas density and on the laser polarization were investigated. When the laser polarization was changed from a linear to a circular polarization, the degree of polarization was decreased. When the initial gas density was increased, the degree of polarization was decreased.

• Korean Journal of Optics and Photonics
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• v.18 no.5
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• pp.367-372
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• 2007

Cervical dysplasia induces morphologic changes in the cervical epithelium which involve changes in the nuclear/cytoplasmic (N/C) ratio. Since the nucleus is one of the significant scattering sources, the N/C ratio change reflects the degree of circular polarization (DOCP) with the depth of signals. Therefore, we used the polarization-sensitive OCT (PS-OCT) technique to measure the polarization changes caused by scattering. Cervical tissues were obtained from a high-grade squamous intraepithelial lesion (H-SIL) of one woman and from low normal women. We obtained the mean of the DOCP as a function of depth in the cervix and quantified the change ratio of the DOCP using slopes that were determined by linear fits in the epithelium layer. We found that DOCP of H-SIL decayed faster than that of normal tissue because of the higher scattering in H-SIL as expected. This result indicates that the PS-OCT system might be useful in measurements of change ratio of DOCP with depth for screening of cervical dysplasia.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.85-91
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• 2010

In this paper, a new microstrip antenna using asymmetric U-shaped slotted ground is proposed for a switchable circular polarization sense. The proposed antenna is achieved a circularly polarization from orthogonal E-field distributions with 90 degree phase difference due to the asymmetrical U-shaped slot. Moreover, the circular polarization sense of the proposed antenna can be easily switchable with changing the symmetric plane of the U-shaped slots. As a result, the proposed antenna is implemented by two PIN diodes with two different bias condition for ON/OFF states. The measured axial ratios are about 1.5 dB without the dependence of the polarization sense and 3-dB axial ratio bandwidth are achieved 29 MHz with respect to about 1.2 % at 2.46 GHz operating frequency.

• Current Optics and Photonics
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• v.3 no.4
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• pp.275-284
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• 2019

Chirality is ubiquitous in physics and biology from microscopic to macroscopic phenomena, such as fermionic interactions and DNA duplication. In photonics, chirality has traditionally represented differentiated optical responses for right and left circular polarizations. This definition of optical chirality in the polarization domain includes handedness-dependent phase velocities or optical absorption inside chiral media, which enable polarimetry for measuring the material concentration and circular dichroism spectroscopy for sensing biological or chemical enantiomers. Recently, the emerging field of non-Hermitian photonics, which explores exotic phenomena in gain or loss media, has provided a new viewpoint on chirality in photonics that is not restricted to the traditional polarization domain but is extended to other physical quantities such as the orbital angular momentum, propagation direction, and system parameter space. Here, we introduce recent milestones in chiral light-matter interactions in non-Hermitian photonics and show an enhanced degree of design freedom in photonic devices for spin and orbital angular momenta, directionality, and asymmetric modal conversion.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.6
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• pp.497-500
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• 2017

This paper proposes a circularly polarized microstrip antenna using an I-shape ground slot perturbation and a perpendicular feeding network. The proposed antenna consists of the symmetrical and perpendicular feeding and the microstrip square radiator loaded with the I-shape ground slot perturbation. The left-handed circular polarization(LHCP) formed by a 90-degree phase difference can be radiated by the perpendicular feeding network and the ground slot perturbation. An implemented antenna is designed for the use in the satellite communication system operated in S-band of 2.2 GHz, and is to be the 91 MHz of -10 dB bandwidth. The measured results of the antenna gain, far-field radiation pattern, and axial ratio agree well with the simulation results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.3 s.118
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• pp.315-322
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• 2007

In this paper, active integrated antenna with left hand circular polarization(LHCP) for a transmitter of UHF RFID reader has been described. A novel rectangular ring patch as a radiator of the active antenna is proposed for easier impedance matching, smaller patch size, and LHCP characteristics. An amplification circuit is placed in the opening area of the radiator and is combined with it to work as oscillating circuit around 915 MHz. From the test results, impedance bandwidth of 29 MHz, 3 dB axial ratio bandwidth of 20 MHz, 3 dB beamwidth of 85 degree, and effective radiation power of 8.8 dBm have been obtained.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.2
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• pp.28.3-29
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• 2015

$Ly{\alpha}$ nebulae, or "$Ly{\alpha}$ blobs", are extended (~100 kpc), bright (L[$Ly{\alpha}$] ~ 1044 erg/s) clouds of $Ly{\alpha}$-emitting gas. The origin of the $Ly{\alpha}$ emission remains unknown, but recent theoretical work suggests that measuring the polarization could discriminate among powering mechanisms. we will discuss current status of $Ly{\alpha}$ polarization observations at high-redshift and our on-going survey program. We will present the first narrow-band, imaging polarimetry of a $Ly{\alpha}$ blob, B3 J2330+3927 at z=3.09, with an embedded, radio-loud AGN (C. You et al. in prep.). The AGN lies near the blob's $Ly{\alpha}$ emission peak and its radio lobes align roughly with the blob's semi-major axis. With the SPOL polarimeter on the MMT telescope, we map the polarization in a grid of circular apertures of radius 0.6" (4.4 kpc), detecting a significant (>$2{\sigma}$) polarization fraction P% in 10 apertures and achieving strong upper-limits (as low as 2%) elsewhere. The degree of the polarization map increases from P% ~ 5% at ~5 kpc from the blob center to ~20% at the outer part (~30 kpc). The detections are distributed asymmetrically, roughly along the blob's major axis. The polarization angles (${\Theta}$) are mostly perpendicular to this axis. These results are consistent with the picture that $Ly{\alpha}$ photons produced at the AGN (or the host galaxy) are resonantly scattered away from the center. Higher polarization fraction on the radio jet suggests that the gas is more optically thin along the jet than the off-axis region.

• Journal of IKEEE
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• v.13 no.3
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• pp.72-79
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• 2009

This paper describes a compact microstrip active antenna with dual polarization. The antenna, receiving both a left-hand circularly polarized wave and a right-hand circularly polarized wave, has a function of polarization diversity. A square-shaped empty room is located on the inside of the microstrip radiator so that the size has been reduced. And slots are added around feeding point to improve input matching. Also, amplifier and switching circuitry are placed at the empty room to increase antenna gain and to select one of the circular polarizations, respectively. The proposed antenna has been applied to GPS(global positioning system). The measurement results show that it has 10dB-impedance bandwidth, 3dB axial bandwidth of about 50MHz, 3dB beamwidth of 90degree, and gain of 13dBi, respectively, for RHCP. Also, it has 3dB axial bandwidth of about 50MHz, 3dB beamwidth of 84 degree, and gain of 12dBi, respectively, for LHCP.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.7
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• pp.1537-1543
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• 2010

This paper describes a compact microstrip antenna with dual polarization characteristics. The antenna, receiving both a left-hand circularly polarized(LHCP) wave and a right-hand circularly polarized(RHCP) wave, can be used for a polarization diversity. A diamond-shaped patch with internal empty room is designed for impedance matching as well as size reduction. And slots are added around feeding point to improve input matching. The proposed antenna has been applied to GPS(global positioning system), operating at 1.57GHz. And, the proposed idea has been verified and estimated by simulation. The measurement results show that it has VSWR 2:1 bandwidth of 83MHz, 3dB axial bandwidth of about 58MHz, 3dB beamwidth of 90degree, and gain of 0dBi, respectively, for RHCP. Also, it has similar performances for LHCP.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.2
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• pp.113-121
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• 2013

In this paper, quadruple polarized antenna system with a reconfigurable feeding network is presented. The proposed antenna system consists of the reconfigurable feeding network for fourth polarization such as vertical/horizontal linear polarization and right-handed/left-handed circular polarizations or 45 degree tilted vertical/horizontal linear polarization and patch antenna to receive the signals with various polarizations. In order to receive a signal in any direction, the proposed antenna is designed by electrical switches for reconfigurable polarization. The insertion loss of the designed feeding network in the proposed antenna system is approximately 1.2 dB. The measured 3 dB axial bandwidth and gain of the proposed antenna are about 2 % and 4 dBi(c).