• 조명전기설비학회논문지
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• 제26권6호
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• pp.8-15
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• 2012

In this paper, we investigated possible optical parameters causing deviation of experimentally observed output spectra from theoretically predicted results in a high-order fiber comb filter based on a polarization-diversity loop configuration. They include wavelength dependency of half-wave plates (HWPs) inserted in the filter for wavelength switching and the modal birefringence of single-mode fibers (SMFs) with which optical components comprising the filter are connected. In order to consider the effect of the modal birefringence of the SMF on a filter performance, it is modeled as a low birefringence fiber with an arbitrary orientation angle and birefringence. It is found from the simulation results that the modal birefringence of SMFs strongly affects the spectral characteristics of the filter and decreases the extinction ratio of the filter, compared with the wavelength dependency of HWPs. In particular, it is also confirmed that the spectral deviation and asymmetric distortions of side-lobes in narrow band transmission spectra result mainly from the modal birefringence of SMFs.

• Journal of the Optical Society of Korea
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• 제2권2호
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• pp.64-73
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• 1998

We have theoretically analyzed and experimentally observed the effects of wavelength dependent birefringence inside a laser cavity on the output characteristics of fiber lasers with a figure eight geometry. The spectral and polarization characteristics of fiber lasers are found to be very susceptible to the resultant birefringence composed of the intrinsically existing wavelength dependent birefringence and the externally induced birefringences inside the fiber. For the variation of twist-induced birefringence inside the nonlinear amplifying loop mirror, the laser output power and center wave-length of continuous wave lasers change periodically, but the polarization characteristics remains nearly unchanged. The changes of the birefringence inside the linear loop has little effect on the spectral characteristics but changes the polarization properties such as the polarization direction.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.617-620
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• 1999

In this study, the polarization e(fecal and the birefringence effect of amorphous germanium (a-Ge) thin films were investigated by using linearly polarized He-Ne laser beam. The a-7e thin films were deposited on the quarts substrate by plasma enhanced chemical vapor deposition (PECVD) and thermal vacuum evaporation In order to obtain the optimum grating arrays, inorganci resists such as Si$_3$N$_4$ and a-Se$_{75}$ Ge$_{25}$ , were prepared with the optimized thickness by Monte Carlo (MC) simulation. As the results of MC simulation, the thickness ofa-Se$_{75}$ Ge$_{25}$ resist was determined with Z$_{min}$ of 360$\AA$ . The resists were exposed to Ga$^{+}$-FIB with accelerating energies of 50 keV, developed by wet etching, and a-Ge thin film was etched by reactive ion-etching (RIE). Finally, we were obtained grating arrays which grating width and linewidth are 0.8${\mu}{\textrm}{m}$, respectively and we studied the polarization and birefringence effect in transmission grating array made of high refractive amorphous material, and the applicability as waveplates and polarizers in optical device.e.e.

• Journal of the Optical Society of Korea
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• 제18권4호
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• pp.365-369
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• 2014

We present accurate analytical solutions of the lineshapes of birefringence (rotation) and dichroism (absorption) spectroscopy for a circular anisotropic medium composed of atoms of the transition $J_g=0{\rightarrow}J_e=1$. The susceptibility of a weak probe beam was analytically calculated and was averaged over a Maxwell-Boltzmann velocity distribution. The lineshapes of the two spectroscopies were then presented in analytical forms at arbitrary values of the linewidths of the inhomogeneous (Doppler) broadening and the homogeneous (natural) broadening of the atoms.

• 천문학회지
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• 제47권1호
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• pp.15-39
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• 2014

Polarization is a basic property of light and is fundamentally linked to the internal geometry of a source of radiation. Polarimetry complements photometric, spectroscopic, and imaging analyses of sources of radiation and has made possible multiple astrophysical discoveries. In this article I review (i) the physical basics of polarization: electromagnetic waves, photons, and parameterizations; (ii) astrophysical sources of polarization: scattering, synchrotron radiation, active media, and the Zeeman, Goldreich-Kylafis, and Hanle effects, as well as interactions between polarization and matter (like birefringence, Faraday rotation, or the Chandrasekhar-Fermi effect); (iii) observational methodology: on-sky geometry, influence of atmosphere and instrumental polarization, polarization statistics, and observational techniques for radio, optical, and $X/{\gamma}$ wavelengths; and (iv) science cases for astronomical polarimetry: solar and stellar physics, planetary system bodies, interstellar matter, astrobiology, astronomical masers, pulsars, galactic magnetic fields, gamma-ray bursts, active galactic nuclei, and cosmic microwave background radiation.

• 한국광학회지
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• 제17권5호
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• pp.430-436
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• 2006

1550nm 파장대역에서 편광에 관계없이 동작하는 $Ti:LiNbO_3\;2{\times}2$ 삽입/분기 광 멀티플렉서를 구현하였다. 소자는 두 개의 입 출력 광도파로, 두 개의 편광모드분리기, 두 개의 편광모드 변환기 그리고 전기광학효과로 파장을 가변시킬 수 있는 전극으로 구성되었다. TE, TM 편광에 대해서 단일모드 특성을 갖는 채널 광도파로는 x-cut $LiNbO_3$에 Ti 확산 방법으로 제작하였으며, 채널 광도파로 위에 배열된 $SiO_2$ 패드의 전단 스트레인을 이용하여 위상정합 편광모드변환기를 구현하였다. 한편 전기광학효과를 이용하여 파장을 가변시키기 위해서 전압을 인가하여 광도파로의 복 굴절률을 변화시켰다. 0.094nm/V 파장가변률과 최대 17nm 파장을 가변시켰으며, 8.2dB 부 모드레벨과 3.72nm FWHM을 측정하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제50권1호
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• pp.6-10
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• 2001

In this study, we investigated the optical properties of sub-wavelength a-Si thin film transmission gratings, especially the polarization effect, the phase difference and the birefringence by using linearly polarized He-Ne laser beam (632.8nm). The a-Si transmission grating of the thickness $of < 0.1 \mum$ with four-type period($\Lambda = 0.4 \mum and 0.6 \mum$ for sub-wavelength and $\Lambda = 1.0 \mum and 1.4 \mum$ for above-wavelength) on quartz substrates have been fabricated using 50 KeV Ga+ Focused-Ion-Beam(FIB) Milling and $CF_4$Reactive-Ion-Etching(RIE) method. Finally, we obtained the trating array of a-Si thin film with a period $0.4 \mum, 0.6 \mum, 1.0 \mum, 1.4 \mum$ which have nearly equal finger spacing and width, sucessfully. Especially, for gratings with $\Lambda = 0.6 \mum(linewidth=0.25 \mum, linespace=0.35\mum), the \etamax at \theta_в=17.0^{\circ}$ is estimated to be 96%. As the results, we believe that the sub-wavelength grating arrayed a-Si thin film has the applicability as the optical device and components.

• 대한의용생체공학회:의공학회지
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• 제27권6호
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• pp.310-317
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• 2006

Extensive research with polarimetry and Mueller matrix has been done for chemical measurements and possible cancer detection. However, the effect of thermally denatured biological tissue on polarization changes is not well known. The purpose of this study is to characterize polarization changes in collagen due to thermal denaturation. The variations in polarized state caused by thermal damage were investigated by obtaining the Mueller matrix elements of collagen sample at multiple thermal damage levels. The changes in birefringence of denatured collagen were also investigated. This information could be used to determine the extent of thermal damage level of clinically heat treated tissues.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 추계종합학술대회 논문집(2)
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• pp.253-256
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• 2000

We report the experimental results for the coupling properties of the an side-polished single-mode fiber covered with metal-clad planar waveguide. The experimental results show that the large birefringence of a metal-clad planar waveguide facilitates the effective separation of TE and TM polarization in the spectral domain. Additionally the resonant wavelengths of the device are tuned based in the thermo-optic effect of polymer planar waveguide.

• 조명전기설비학회논문지
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• 제17권6호
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• pp.72-76
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• 2003

편광분석법을 이용한 광섬유형 전류센서를 구성하여 다양한 전류측정 실험을 행하였다. 잔존 선형복굴절의 영향을 최소화하기 위하여 광섬유 센서 코일의 한쪽 끝에 Faraday 미러를 장착하였으며 일반적인 미러를 사용하는 경우와 출력의 안정성을 비교분석 하였다. 센서코일에 변형을 가하는 경우나 장시간에 걸친 안정성 실험에서도 Faraday 미러를 사용하는 경우에 출력의 안정성이 현저하게 증가함을 알 수 있었다.