• Proceedings of the Optical Society of Korea Conference
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• 2007.07a
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• pp.179-180
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• 2007

• Proceedings of the Optical Society of Korea Conference
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• 2005.07a
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• pp.194-195
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• 2005

• Proceedings of the Optical Society of Korea Conference
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• 2001.08a
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• pp.188-189
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• 2001

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.252-253
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• 2004

• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.6
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• pp.87-96
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• 1999

For analog optical transmission of narrow-band microwave signal, a novel all-optical linearization technique of electro-absorption (EA) optical modulator by using dual modulation scheme is proposed and theoretically investigated. By using the dual modulation scheme where the sub-modulator has a different length, DC bias and band-gap wavelength, the DC bias operation point where the third-order intermodulation products of ~30dB and the following increase of spurious free dynamic range (SFDR) of ~20dB wave achieved in sub-octave narrow band operation.

• Electrical & Electronic Materials
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• v.4 no.3
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• pp.249-258
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• 1991

He-Ne레이저(.lambda.=0.6328[.mu.m])를 광원으로 사용하는 y-cut LiNbO$_{3}$기판의 광 도파로 형성 과정을 빔 전송방식 메카니즘을 이용하여 광 도파로에서 광파의 전계 변화 및 전계 분포에 대하여 시뮬레이션 하였다. 그리고 Xl(55[.mu.m])* Zl(5000[.mu.m])인 LiNbO$_{3}$기판의 광 도파로 폭을 4[.mu.m], 버퍼층을 0.02[.mu.m]로 하였을때 도파로 층의 깊이가 0.2[.mu.m]인 지점에서 인가전압에 대한 x방향의 전계(E$_{x}$)와 y방향의 전계(E$_{y}$ )분포를 관찰하였다. 또한 단일 도파로의 파라미터 조건을 적용하여 X-스위치를 구성하였을때 전계를 인가하지 않은 상태에서 굴절율 변화(dn) 0.002, 도파로 폭(w) 3[.mu.m]로 하여 도파로의 교차각(.alpha.)을 0.4.deg.~0.6.deg.로 변화시킨 경우, .alpha.=0.5.deg.와 0.6.deg.일 때는 광빔이 bar측으로 출력되었고 .alpha.=0.4에서는 광빔이 cross측으로 출력 됨을 확인하였다. 따라서 위에서 확인된 도파로의 교차각 .alpha.=0.4.deg.인 경우, 전극간격(gap)이 2[.mu.m]인 조건에서 스위칭 전압을 인가하였을 때 25[V]에서 전기광학 효과에 의하여 광빔이 cross측에서 bar측으로 변조됨을 확인함으로써 X-스위치 광변조기의 기본적인 설계조건을 구현하였다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1782-1792
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• 1994

Ti : $LiNbO_3$ traveling-wave phase optical modulators at wavelength 1.3㎛ have been designed and fabricated, focusing on the optical waveguide and asymmetric coplanar electrode structure. To improve the phase-mismatch of traveling-wave ACPS electrode, the characteristic impedance, effective microwave index, and electrode loss have been presented as a function of geometric parameters including electrode and buffer layer thickness. Low-loss channel optical waveguides on $LiNbO_3$ were fabricated by the Ti diffusion method with $O_2$ water-vapor environment. $2.5{\mu}m$ thick electrode was successfully fabricated by double-spin image reversal process. Modulation bandwidth was limited by a resonance at 2.9 GHz and modulation bandwidth up to 2.5GHz was approxirnately measured.

• Korean Journal of Optics and Photonics
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• v.13 no.6
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• pp.530-536
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• 2002

The accurate measurements of thermal expansion coefficients is one of the most important techniques required not only in material science but also in industries. A high precision interferometric dilatometer, using acoustic optical modulator, has been constructed and its performance has been tested. The system consists of a double-path optical heterodyne interferometer and a radiant heating furnace. This provides highly accurate length measurement, and allows rapid heating and cooling method for the specimen. A three longitudinal mode frequency stabilized He-Ne laser, using the secondary beat frequency, is constructed. Its stability is found to be $5{\times}10^{-9}$. The uncertainty in the length measurement is estimated to be of nanometer order in the range between room temperature to 1100 K.

• Korean Journal of Optics and Photonics
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• v.14 no.5
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• pp.545-554
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• 2003

Design of the optical modulator composed of a three-waveguide coupler and CPW traveling-wave electrodes was carried out. Switching phenomena of three-waveguide couplers were analyzed by using the coupled mode theory, and the coupling-lengths of the devices were calculated by means of the FDM. CPW traveling-wave electrodes were analysed by the CMM and SOR simulation technique in order to find the conditions of phase-velocity and impedance matching. Traveling-wave modulators were fabricated on z-cut LiNbO$_3$ substrate. Ti was in-diffused in LiNbO$_3$ to make waveguides and Au electrodes were built on the waveguides by the electrolyte technique. The fabricated modulator chip was end-polished, pig-tailed and packaged in a brass mount with K-connector. The insertion loss and the switching voltage of the optical modulator were about 4㏈ and 19V, respectively. Network analyzer was used to obtain the S parameter and the corresponding RF response. From the measurement, parameters of the traveling-wave electrodes were extracted to be Z$_{c}$= 45 Ω, N$_{eff}$=2.20, and $\alpha$$_{0}$=0.055/cm√GHZ. The measured optical response R($\omega$) was compared with the theoretically estimated one, showing both responses agree well. The measurement results revealed that 3㏈ bandwidth turned out to be about 13 GHz.

• Korean Journal of Optics and Photonics
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• v.15 no.4
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• pp.375-384
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• 2004

Switching phenomenon of a three-waveguide optical coupler was analyzed by using the coupled mode theory, and the coupling-length of the device was calculated by means of the FDM. CPW traveling-wave electrodes were designed by the CMM and SOR simulation techniques so as to satisfy the conditions of phase-velocity and impedance matching. Traveling-wave modulators were fabricated on a z-cut LiNbO$_3$ substrate. Ti was in-diffused in LiNbO$_3$ to make waveguides and Au electrodes were built on the waveguides by the electroplating technique. Insertion loss and switching voltage of the optical modulator were about 4 ㏈ and 15.6V. Network analyzer was used to obtain S parameters and corresponding RF response. From the measurement, parameters of the traveling-wave electrodes were extracted as such Z$_{c}$=39.2 $\Omega$, Neff=2.48, and a0=0.0665/cm((GHz) (1/2)). The measured optical response R(w) was compared with the theoretically estimated and both responses were shown to agree well. The measurement results revealed that the ㏈ bandwidth turned out to be about 13 GHz.