• Proceedings of the Optical Society of Korea Conference
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• 1990.02a
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• pp.150-153
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• 1990

Nitrobenzene과 Isooctane 임계혼합용액의 정전기장에 의한 유도복굴절을 임계점 근처에서 Oc-Kerr 효과로 관측하여 Kerr 상수가 발산하는 임계특성을 알아 보았다. 그리고 여기서 Kerr 상수에 대한 임계지수와 복굴절의 오름시간에 관계되는 임계지수를 결정하였다. 또한 복굴절 신호를 살펴본 결과 연속적인 정전기장의 펄스에 대해 기억효과가 있음을 보았다.

• Journal of the Korean Society for Nondestructive Testing
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• v.26 no.5
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• pp.336-342
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• 2006

Uniaxial stress in ail axisymmetric body is the simplest example of ultrasonic stress measurement. However, the birefringence theory cannot be applied for axisymmetric solids because the axisymmetric stress field in the body does not make shy velocity difference in SH waves propagating in the axisymmetric direction. Conventional ultrasonic technique using the time-of-flight method also needs ultrasonic lengths of the unstressed and stressed body, which is very impractical. In this paper, the birefringence effect in axisymmetric solids under uniaxial stress is formulated to evaluate the axial stress inside the solid without measuring tile ultrasonic length. Theoretical derivation for the birefringence characteristics in the axisymmetric solids is made using the longitudinal and shear waves instead of two horizontally polarized shear waves. Tension test is conducted for carbon-steel specimen to measure the birefringence coefficient and investigate the validity of the theory. It is observed from experimental results that the velocity difference in two differently polarized acoustic waves is proportional to the uniaxial stress in the axisymmetric solid with a good agreement with the theoretical value.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.104-105
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• 2000

다이오드 레이저로 펌핑되는 Nd:YAG 매질에 형성된 열 복굴절은 레이저 출력과 빔질의 저하를 초래한다. 선편광된 레이저 출력을 얻기 위해서는 주로 공진기 내에 선형 편광자를 삽입하게 되는데, 레이저 매질에 형성된 열 복굴절에 의한 왜곡 편광된 레이저 빔이 편광자에 의해 반사되어 공진기 손실을 초래한다. 편광 왜곡에 의한 레이저 빔의 손실을 줄이거나 이중 초점을 제거하기 위해 주로 사용되어지는 광 소자는 Faraday 회전자, λ/4 판, 석영 회전자 등이 사용되어진다.$^{(1-5)}$ 90$^{\circ}$ 석영 회전자와 Faraday 회전자는 공진기 내에 두 개의 동일한 구조를 갖는 레이저를 이용할 경우 사용되고 λ/4 판 과 45$^{\circ}$ Faraday 회전자는 주로 단일 레이저 헤드의 복굴절 보상을 위해 사용되어진다. 45$^{\circ}$ Faraday 회전자는 이론적으로 완벽히 열복굴절에 의한 편광 왜곡을 보상한다. 그러나, 열복굴절을 완벽히 보상하기 위해서는 레이저 빔이 항상 레이저 매질의 같은 지점을 통과해야 한다. 실제적으로 레이저 매질에서는 열에 의한 열 렌즈 효과가 있기 때문에 레이저 빔이 항상 같은 지점을 통과하지 않게 된다. 이런 문제를 해결하기 위해 공진기 내에 열 렌즈 효과를 보상하기 위한 렌즈를 삽입하거나 레이저 헤드를 공진기 거울 가까이 설치하여야 한다. Faraday 회전자는 길이가 길기 때문에 레이저 헤드를 공진기 거울 가까이 설치하기는 어렵고 항상 열 렌즈 효과를 보상해주는 광학 소자가 있어야 하는 단점이 있다. 반면 λ/4 판은 완벽한 편광 왜곡을 보상해주지 않아 레이저 손실을 초래하지만 두께가 얇아 레이저 헤드와 공진기 거울을 근접해서 설치할 수 있어서 몇몇 연구자에 의해 연구되어 졌다.$^{(3)}$ 본 연구에서는 λ/4 판을 이용하고 편광기에서 반사된 빔을 공진기에 되반사 시키는 구조를 사용하여 선 편광된 레이저의 출력과 빔의 질을 개선 시켰다. (중략)

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.5 no.1
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• pp.31-39
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• 1991

The polarization properties of low birefringent optical fiber due to intrinsie birefringence and magnetooptic effects are theoretically analyzed and experimented. The low birefringent fiber is fo¬und to have more excellent polarization maintaining properties than normal single mode optical fiber. As the experimental results, the polarizability of low birefringent optical fiber is measured over 0.818. The variation of output polarization angle with input polarization angle is measured within $9^{\circ}$. Imple¬mented magnetic field measuring system using low birefringent optical fiber can linearly measure the magnetic field strength up to lOkAT generated by solenoid. The maximum error is 1.95% in the magnetic field strength of 4kAT.

• Korean Journal of Optics and Photonics
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• v.9 no.5
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• pp.307-314
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• 1998

We have studied the effects of interface on polarization dependence of waveguide and designed the polarization independent 2-dimensional waveguides on InP for arrayed waveguide grating. To figure out the effects of interface on polarization dependence, we have solved the 1-dimensional wave equation using a transfer matrix method. It is shown that the birefringence becomes stronger as the number of interfaces increases. In order to design polarization independent 2-dimensional waveguides, we have used effective index method. The structures considered are ridge type, raised strip type, and buried type waveguide. In the cases of ridge and raised strip type, conventional effective index method was used. In the case of buried type corrected effective index method was used. We have determined the height and width of waveguides such that the waveguides become polarization independent.

• Korean Journal of Optics and Photonics
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• v.8 no.6
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• pp.450-455
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• 1997

A pulsed Ti:sapphire laser with a Z-folded cavity, which was pumped by a freqeuncy-doubled Nd:YAG laser, was developed. It shows 120 nm wavelength tuning range from 740 nm to 860 nm with 90 nm FWHM under a pumping energy of 3 mJ with 18% output coupler. Using a birefringent filter, the effective efficiency was improved about 10 times compare to without a birefringent filter. The output energy obtained was $\365mu$Jwith 4 nm FWHM. And the wavelength tuning range was broadened to about 160 nm within an output energy fluctuation of $\pm$10%.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2007.05a
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• pp.342-345
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• 2007

본 연구에서는 광섬유형(Fiber Optic Current Sensor) 광전류센서 구성 시 발생하는 선형복굴절(Linear Birefringence)의 보상에 용이한 수직원형틀(Orthogonal Loop Type) 센서헤드(Sensor Heads)를 개선하여 1 Cross 수직원형틀(l Cross Orthogonal Loop Type)을 제시하였다. 그리고 기존의 페루프형 원형틀 (Closed Loop Type), 수직원형틀 그리고 1 Cross 수직원형틀의 편광상태를 비교하였다. 그 결과 편광상태 측정 시 페루프 원형틀을 수직원형틀로 교체할 경우 15.3%, 1 Cross 수직원형틀로 교체할 경우 33.8%의 선형복굴절 감소 효과가 나타났다. 이에 1 Cross 수직원형틀을 광전류센서에 적용할 경우 안정된 편광특성으로 고신뢰성 광전류센서 개발 가능성을 높게 할 것이다.

• Korean Journal of Optics and Photonics
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• v.8 no.2
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• pp.128-133
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• 1997

The effects of twist induced birefringence on the polarization properties of Er and Nd fiber laser with a linear type cavity were experimentally observed and theoretically analyzed. As the twist rate increases, the polarization states of the polarization eigenmodes are found to be always linear, and their frequencies gradually coincide with each other, and their polarization directions rotate at about half of twist rate at large twist rates.

• Korean Journal of Optics and Photonics
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• v.8 no.2
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• pp.161-164
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• 1997

A new hybrid, heterodyne, fiber-optic electric field sensor scheme is presented. In this scheme, a dual polarization, dual frequency, stabilized He-Ne laser is used for the light source of the interferometer, Probe beam is delivered to the sensor head using polarization maintaining fiber. In the sensor head, $LiTaO_3$ electro-optic crystal is used for sensing element. Phase retardation is induced on the dual frquency, dual polarization probe beam due to applied electric field across the crystal. Induced phase retardation is demodulated by in-phase and quadrature demodulation technique. In this way, we can obtain optimum sensitivity for electric field measurement regardless a quasi-static phase difference between two polarization components.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.10
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• pp.1158-1165
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• 1988

In this paper, the polarization properties of spun fiber due to intrinsic birefringence and magneto-optic effects are theoretically analyzed and experimented. The degree of polarization which indicates the intrinsic birefrigence is measured over 0.818, and the variation of output polarization angle with input polarization angle is measured within 9$^{\circ}$. Compared with single mode fiber, spun fiber is found to have very excellent polarization-maintaining property. Implemented current measurement system using spun fiber can linearly measure the magnetic field up to 20,000 A/m generated by solenoid.