• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.423-427
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• 2003

Effect of the thermal poling on the 1.55 fm emission spectra in various Er$^{3+}$ -doped glasses was investigated with a special attention on the changes in the values of FWHM(Full Width at Half Maximum) intensity. Tellurite glasses poled at 28$0^{\circ}C$ with an electric voltage of 4 kV resulted in an approximately 6% increase in FWHM values compared with their unpoled counterparts. On the other hand, values for glasses, such as aluminosilicate, sulfide and chalcohalide, either decreased or remained unchanged. The characteristic results from tellurite glasses are most probably due to the presence of lone-pair electrons in the TeO$_4$ hi-pyramidal units that form the main network structure of tellurite glasses.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.1
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• pp.27-32
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• 2014

In this paper, PZT piezoelectric ceramic specimens with 4 compositions (Zr/Ti=50/50, 53/47, 56/44, 58/42) in $Pb(Zr,Ti)O_3$ system were fabricated. We studied effects of poling strength and thermal aging on the temperature characteristics of eletromechanical coupling factor k31 of the specimens, which were poled with the DC electric fields, 1.5, 2.5 and 3.5 kV/mm respectively and thermally aged for an hour at $200^{\circ}C$. The eletromechanical coupling factor k31 of the specimen with the composition Zr/Ti= 53/47, nearest to the morphotropic phase boundary decreased the most greatly, irrelevant to the intensity of poling field, due to 1st thermal aging. And the temperature coefficient of eletromechanical coupling factor k31 was (-) in the tetragonal phase composition and (+) in the rhombohedral phase composition, which is reverse in the temperature coefficient of resonance frequency. It is interesting that eletromechanical coupling factor k31 of PZT ceramics is shown to be able to increase as temperature increase in the interval $-20{\sim}80^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.6
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• pp.491-496
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• 2010

The relaxation behavior of aligned electric dipoles in a mixed polymer of P2ANS with P(VDF-TrFE) is studied with optical second harmonic generation (SHG). In this work, a macroscopic noncentrosymmetry of the spin coated film was achieved by an electrical poling. The relaxation of induced polar order of nonlinear optic(NLO) chromophores after poling leads to an insufficient long-term stability of NLO properties. In this work, we develop a new technique to suppress such kind of dipole relaxation in a poled polymer. We found that the poled dipoles in a NLO polymer were effectively immobilized by the internal electric field created by a thermally annealed ferroelectric polymer. The long-term stability in a mixed system of NLO polymer/ferroelectric polymer was successively accomplished by a series of thermal treatments applied to the mixed polymer system at a temperature of $140^{\circ}C$ for at least 1hour after poling.

• Journal of the Korean Ceramic Society
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• v.36 no.12
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• pp.1374-1380
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• 1999

The cause of Scond Harmonic Generation (SHG) in thermally poled silica glass is suggested basedon the electrical and dielectric relaxation measurements. The absorption currents as functions of time were measured for various types of silica glasses and analyzed by the theory of Space Charge Polarization. Space charge polarization occurs when an ionic conducting material is subjected to dc electric field with blocking electrode. Thermal poling performed to induce SHG in silica glass is basically identical to the process generating space charge polarization. Hence it was found that gene-ration removal reproduction and temperature dependence of SHG in poled silica is directly related to those of space charge polarization. It turned out that the fundamental parameters governing the SHG in poled silica are charge carrier concentration and mobility. Based on the theory of space charge polarization and experimental results of electrical rela-xation the method to increase the intensity of SHG is proposed.

• Journal of the Korean Ceramic Society
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• v.26 no.1
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• pp.43-50
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• 1989

This experiment was conducted to investigate correlation between microstructure and electrical properties according to Zr/Ti mole ratio in Rhombohedral Phase PZT. Domain behavoir was investigated by the change of thermal expansion coefficient. Piezoelectric properties, the temperature dependence of dielectric constant and the change of dielectric constant before and after poling were measured. Crystal structure, the measurement of lattice parameter were carried by X-ray analysis. Domain pattern before and after poling was examined by SEM.

• Journal of the Korean Ceramic Society
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• v.36 no.9
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• pp.923-929
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• 1999

The cause of optical nonlinearity induced in thermally poled silica glass is believed to be the space charge polarization. Since the second order optical nonlinearity (electro-optic effect) can be used in optical switches the optical nonlinearity in silica glass has drawn a large attention. Space charge polarization occurs when an ionic conducting material is subjected to dc electric field by the blocking electrode. Thermal poling performed to induce the optical nonlinearity in silica glass is basically identical to the process generating space charge polarization. As a first step to understand the mechanism of space charge polarization in silica glass hence the induced optical nonlinearity the absorption currents as functions of time were measured for various types of silica glasses and analyzed by the theory of space charge polarization. It was found that the electrical relaxation exhibited a step by the space charge polarization in the relatively long time range and dielectric loss peak showed a maximum at a specific temperature which is depending on type of silica glass. It was turned out that this relaxation might be a cause of nonlinearity in electrical conductivity of silica glass.

• Bulletin of the Korean Chemical Society
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• v.19 no.11
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• pp.1168-1171
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• 1998

Two kinds of second-order nonlinear optical copolymers were prepared by the copolymerization of the vinyl monomers containing NLO chromophore, methacrylic acid, and methyl methacrylate or butyl methacrylate. Glass transition temperatures (Tg of copolymers were around 130 ℃. The copolymers were soluble in common organic solvents such as tetrahydrofuran (THF), cyclohexanone, and N,N-dimethylformamide (DMF). The crosslinked copolymer was obtained by thermal treatment using pentaerythritol tetrakis(2-mercaptoacetate) as a crosslinker and became insoluble in tetrahydrofuran (THF) and N,N-dimethylformamide (DMF). Poling was carried out at 120 ℃ for 20 min and identified with UV-Vis spectroscopy. Electro-optic coefficient (r33) measurement showed a value of 35 pm/V for polymer 2 at 633 nm. Temporal stability of copolymers was improved owing to the crosslinked network, which was successfully obtained at 170 ℃ for 30 min after poling.

• Korean Journal of Optics and Photonics
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• v.9 no.4
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• pp.215-220
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• 1998

We proposed an in situ measurement set-up and technique to measure the various electro-optic(E-O) properties of the E-O polymer. Using the proposed measurement set-up, the electro-optic effect and birefringence of unpoled side-chain E-O polymer induced by the strong dc and ac electric field were observed. The dependence of the E-O coefficients on the various poling conditions were measured with real time. To evaluate the thermal stability of the poled polymer the relaxation of the E-O effect was measured and the result was compared with well known polymer materials. The proposed measurement reduces the number of experimental steps and saves measurement time.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.115-118
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• 2000

Uncooled pyroelectric infrared detectors based on BST(B $a_{-x}$S $r_{x}$Ti $O_3$) thin films have been fabricated by RF magnetron sputtering and surface Micromachining technology. The detectors form BST thin film ferroelectric capacitors grown by RF magnetron sputtering on N/O/N(S $i_3$ $N_4$/ $SiO_2$/S $i_3$ $N_4$) membrane. The sputtered BST thin film exhibits highly c-axis oriented crystal structure that no poling treatment for sensing applications is required. This is an essential factor to increase the yield for realization of an infrared image sensor. surface-Micromachining technology is used to lower the thermal mass of the detector by giving maximum sensor efficiency Gold-black is evaporated on top of the sensing elements used the thermal evaporator. fabricated uncooled pyroelectric infrared detectors is highly output voltage at the low temperature(1$^{\circ}C$).).).

• Journal of the Optical Society of Korea
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• v.16 no.3
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• pp.282-287
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• 2012

In this paper, we have proposed a principle to design a compact and temperature independent electro-optic switch based on a slotted photonic crystal directional coupler (SPCDC). Infiltration of the slotted silicon photonic crystal with polymer enhances the slow light and decreases the switching length, whereas the different signs of thermo-optic coefficients of the polymer and silicon make the proposed switch stable within $25^{\circ}C$ to $85^{\circ}C$ temperature range. The SPCDC structure is modified to increase poling efficiency of the polymer in the slot and to flatten the dispersion diagram of the even mode to minimize the switching length.