• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.282-285
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• 1999

Fabrication and pakaging method for low delve voltage and 10Gbps Ti diffused waveguide LiNbO$_3$ optical intensity modulator are described. Optical waveguides were prepared by conventionaly electron-beam evaporation and Ti-indiffusion into Z-cut plate LiNbO$_3$. Traveling-wave electrodes were used for obtaining the wideband frequency response and impedance matching. Microwave effective index and characteristic impedance measured by time domain reflectometry and compared with the calculated value by conformal mapping. The characteristics of 10Gbps modulator at the 1550nm wavelength are as follows : perfect modulation voltage Is about 5V, optical insertion loss Is about 5dB, 3-dB bandwidth is 10GHz, and characteristic impedance is about 50$\Omega$.

• 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.2
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• pp.146-153
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• 1998

The optical near-field patterns, propagation loss and mode sizes of x-cut $Ti:LiNbO_3$ optical waveguide which was fabricated by Ti-diffusion varying with Ti strip thickness in wet oxygen atmosphere were discussed at optical wavelength 1550nm. As Ti thickness increased from $760{\AA}$, the insertion loss of waveguide was decreased. But at Ti thickness $1500{\AA}$, mode sizes are widely broadened. The Ti thickness of below $1100{\AA}$ and above $1500{\AA}$ showed negative effects to propagation loss and fiber coupling. The best Ti thickness for fabricating low propagation loss and good fiber coupling was inferred to be between $1100{\AA}-1500{\AA}$ in our conditions. And for Ti thickness $1150{\AA}$, its propagation loss, horizontal/vertical mode sizes were showed 1.61 dB/cm, $11.9/8.9{\mu}m$ for TM, 0.22 dB/cm, $12.0/9.1{\mu}m$ for TE respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.477-479
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• 1997

The preparation of mach-zehnder inteferometric optical modulator and the properties of electrode and modulation bandwidth for high speed optical communications were described. The results of fabricated optical modulator was that optical 3-dB bandwidth 4.7GHz, driving voltage 6V and fiber-waveguide-fiber insertion loss 4.5dB for TM mode respectively.

• Korean Journal of Optics and Photonics
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• v.7 no.1
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• pp.51-59
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• 1996

In this paper, we propose a new type of a planar waveguide lens, a meniscus lens instead of a plano-convex lens used widely for the optical integrated circuits such as optical numerical processors. A plano-convex lens has a spherical aberration caused by the linear boundary. In the proposed meniscus lens, this linear boundary is replaced by a circular-boundary, and the spherical aberration is removed. To test the performance of the proposed lens, a meniscus lens is designed using Fermat principle and fabricated on the Y-cut $LiNbO_3$ substrate. First a $Ti:LiNbO_3$ planar waveguide is fabricated on the $LiNbO_3$ substrate by Ti indiffusion. Then a meniscus lens is fabricated on the planar waveguide by TIPE(Ti indiffued proton-exchange) method. A plano-convex lens is also fabricated on the same substrate to compare the spot size at the focal point. The measured spot size of the meniscus lens is reduced to 59% that of the plano-convex lens. This result shows that the proposed meniscus lens is more effective for optical integrated circuits than the plano-convex lens.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.101-104
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• 1998

We report some methods for measuring a LiNbO$_3$ optical phase modulator bandwidth. Since Mach-Zehnder waveguide type, one of methods for modulation bandwidth measurement, is comparatively simple and useful, it was adapted in this work. In order to confirm this method, the waveguide of single and Mach-Zehnder type were fabricated on the same wafer. The Mach-Zehnder interferometric waveguide and the single channel waveguide were used for the measurement of the phase modulator's driving voltage and bandwidth for device fabrications, respectively. Ti-860$\AA$ in-diffusion was achieved in a wet-bubbling oxygen environment at 105$0^{\circ}C$/8hours. LINbO$_3$ internal chips were pigtailed to PMF(polarization maintaining fiber)/SMF(single mode fiber) using an epoxy curing technique. Examined were optical properties such as an insertion loss, propagation loss and mode size, and the loss mechanism of optical coupling between an optical fiber and a waveguide was considered.

• 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.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.128-134
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• 2012

The performance evaluation and fabrication of integrated-optic electric-field sensor utilizing $Ti:LiNbO_3$ asymmetric Mach-Zehnder intensity modulator with a push-pull lumped electrode and a plate-type probe antenna to measure an electric field strength is described. The modulator has a small device size of $46{\times}7{\times}1\;mm$ and operates at a wavelength $1.3{\mu}m$. The devices are simulated based on the BPM software and fabricated utilizing Ti-diffused $LiNbO_3$ channel optical waveguides. The minimum detectable electric field is 1.02 V/m and 6.91 V/m, corresponding to a dynamic range of ~35 dB and ~10 dB at the frequencies of 500 KHz and 5 MHz, respectively.

• Journal of the Optical Society of Korea
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• v.18 no.6
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• pp.739-745
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• 2014

We have demonstrated a $Ti:LiNbO_3$ electro-optic electric-field sensor utilizing a $1{\times}2$ Y-fed balanced-bridge Mach-Zehnder interferometric (YBB-MZI) modulator, which uses a 3-dB directional coupler at the output and has two complementary output waveguides. A dc switching voltage of ~25 V and an extinction ratio of ~12.5 dB are observed at a wavelength of $1.3{\mu}m$. For a 20 dBm rf input power, the minimum detectable electric fields are ~8.21, 7.24, and ~13.3 V/m, corresponding to dynamic ranges of ~10, ~12, and ~7 dB at frequencies of 10, 30, and 50 MHz respectively. The sensors exhibit almost linear response for an applied electric-field intensity from 0.29 V/m to 29.8 V/m.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.425-427
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• 1997

Ti:LiNbO$_3$optical waveguides were fabricated as a function of Ti thickness and pigtailed with polarization maintaining fiber(PMF). The near field patterns and total insertion loss of these sample was showed and measured for optical wavelength 1550nm. The fiber-to-waveguide coupling loss was described also .