• Korean Journal of Optics and Photonics
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• v.4 no.2
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• pp.188-194
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• 1993

By applying the Nakayama's theory of saturation spectroscopy to 87Rb $D_2$ lines, taking into account the optical pumping process, the relative intensities of the resonance signals were calculated for various polarization combinations of pump and probe beams. The saturated absorption spectra were observed with a linewidth-narrowed semiconductor laser. As the result, it was found that the theoretical calculations were in good agreement with the experimental observations in the case where the geomagnetic field was- shielded.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.5
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• pp.1135-1142
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• 2000

In this study, we fabricated a 1.55um polarization-insensitive semiconductor optical amplifier(SOA) with rectangular buried heterostructure using a InGaAsP/InP double heterostructure wafer. Measured characteristics of the fabricated SOA are that 3dR bandwidth is 35nm and 3dB saturation output power is 4dBm. Maximum gain under the 150mA CW driving condition is 19.4dB. We measured the ASE(amplified spontanouse emission) Power spectrum or n and TM mode in the fabricated SOA using ASE measurement system and knew that distributions of the TE and TM mode about the maxinum region are nearly coincident. this shows the fabricated SOA is a polarization-insensitive.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.5
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• pp.370-375
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• 2001

PZT thin films (3500${\AA}$) ahve been prepared onto Pt/Ti/corning glass (1737) substrates with a RF magnetron sputtering system using Pb$\sub$1.50/(Zr$\sub$0.52/,Ti$\sub$0.48)O$_3$ ceramic target. We used two-step annealing techniques, PZT thin films were grown at a 300$^{\circ}C$ substrate temperature and then subjected to an RTA treatment. In case of 500$^{\circ}C$ RTA temperature show pyrochlore phase. The formation of Perovskite phase started above 600$^{\circ}C$ and PZT thin films generated (101) preferred orientation. As the RTA time and temperature increased, crystallization of PZT films were enhanced. The PZT capacitors fabricated at 650$^{\circ}C$ for 10 minutes RTA treatment showed remanent polarization 30 ${\mu}$C/$\textrm{cm}^2$, saturation polarization 42${\mu}$C/$\textrm{cm}^2$, coercive field 110kV/cm, leakage current density 2.83x10$\^$-7/A/$\textrm{cm}^2$, remanent polarization were decreased by 30% after 10$\^$9/ cycles.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.341-344
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• 1999

The effects of post annealing treatments of ferroelectrlclty in PZT(P $b_{1.05}$(Z $r_{0.52}$, $Ti_{0.48}$) $O_3$ thin film deposited on Pt/ $SiO_2$/Si substrate by RF-Magnetron sputtering methode was Investigated. Analyses by RTA(Rapid Thermal Annealing) treatments reveled that the crystallization process strongly depend on the healing temperature. The Perovskite structure with strong PZT (101) plan was obtained by RTA treatments at 75$0^{\circ}C$ With increasing RTA temperature of PZI thin films, the coercive field and remanent Polarization decreased, while saturation polarization( $P_{r}$) was decreased. P-E curves of Pt/PZT/Pt capacitor structures demonstrate typical hysteresiss loops. The measure values of $P_{r}$,. $E_{c}$ and dielectric constants by post annealed at 75$0^{\circ}C$ were 38 $\mu$C/$\textrm{cm}^2$ 35KV/cm and 974, respectively. Switching polarization versus fatigue characteristic showed 12% degradation up to 10$^{7}$ cycles.s.s.s.s.s.s.

• Journal of the Optical Society of Korea
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• v.18 no.4
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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.

• Current Optics and Photonics
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• v.4 no.3
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• pp.174-185
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• 2020

Multiscattering occurs when a laser transmits into dense atmosphere targets (e.g. fogs, smoke or clouds), which can cause depolarization effects even though the scattering particles are spherical. In addition, multiscattering effects have additional information about microphysical properties of scatterers. Thus, multiscattering can be utilized to study the microphysical properties of the liquid water cloud. In this paper, a Monte Carlo method was used to simulate multi-scattering transmission properties of Lidar signals in the cloud. The results showed the slope of the degree of linear polarization (SLDLP) can be used to invert the extinction coefficient, and then the cloud effective size (CES) and the liquid water content (LWC) may be easily obtained by using the extinction coefficient and saturation of the degree of linear polarization (SADLP). Based on calculation results, a microphysical properties inversion method for a liquid cloud was presented. An innovative multiscattering polarization Lidar (MSPL) system was constructed to measure the LWC and CES of the liquid cloud, and a new method based on the polarization splitting ratio of the Polarization Beam Splitter (PBS) was developed to calibrate the polarization channels of MSPL. By analyzing the typical observation data of MSPL observation in the northern suburbs of Nanjing, China, the LWC and CES of the liquid water cloud were obtained. Comparisons between the results from the MSPL, MODIS and the Microwave radar data showed that, the microphysical properties of liquid cloud could be retrieved by combining our MSPL and the inversion method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.3
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• pp.570-576
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• 2007

In this study, the characteristics of metal-ferroelectric-semiconductor FET (MFSFET) device is investigated using field-dependent polarization and square-law FET models. From drain current with the gate voltage variation, when coercive voltages of ferroelectric thin film are 0.5 and 1V, the memory windows are 1 and 2V, respectively. When the gate voltages are 0, 0.1, 0.2 and 0.3V, the difference of saturation drain currents of the MFSFET device at two threshold voltages in ID-VD curve are 1.5, 2.7, 4.0, and 5.7mA, respectively. As a result of the analysis for drain currents after tine lapse, which is based on the simulation for hysteresis loop and the fitting of retention properties of ferroelectric thin films such as PLZT(10/30/70), PLT(10) and PZT(30/70) thin film shows excellent reliability that the decrease of saturation current is about 18% after 10 years.

• Smart Structures and Systems
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• v.30 no.3
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• pp.221-237
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• 2022

This paper is concerned with nonlinear modeling and efficient numerical simulation of electrostrictive materials and structures. Two types of such materials are considered: relaxor ferroelectric ceramics and electrostrictive polymers. For ceramics, a geometrically linear formulation is developed, whereas polymers are studied in a geometrically nonlinear regime. In the paper, we focus on constitutive modeling first. For the reversible constitutive response under consideration, we introduce the augmented Helmholtz free energy, which is composed of a purely elastic part, a dielectric part and an augmentation term. For the elastic part, we involve an additive decomposition of the strain tensor into an elastic strain and an electrostrictive eigenstrain, which depends on the polarization of the material. In the geometrically nonlinear case, a corresponding multiplicative decomposition of the deformation gradient tensor replaces the additive strain decomposition used in the geometrically linear formulation. For the dielectric part, we first introduce the internal energy, to which a Legendre transformation is applied to compute the free energy. The augmentation term accounts for the contribution from vacuum to the energy. In our formulation, the augmented free energy depends not only on the strain and the electric field, but also on the polarization and an internal polarization; the latter two are internal variables. With the constitutive framework established, a Finite Element implementation is briefly discussed. We use high-order elements for the discretization of the independent variables, which include also the internal variables and, in case the material is assumed incompressible, the hydrostatic pressure, which is introduced as a Lagrange multiplier. The elements are implemented in the open source code Netgen/NGSolve. Finally, example problems are solved for both, relaxor ferroelectric ceramics and electrostrictive polymers. We focus on thin plate-type structures to show the efficiency of the numerical scheme and its applicability to thin electrostrictive structures.

• Korean Journal of Optics and Photonics
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• v.17 no.4
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• pp.305-311
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• 2006

We propose a 7-level atom model, which takes into account two-photon coherence effects in saturation absorption spectroscopy. Using this model we explained spectral change with laser intensity and some of crossover resonance lines, which cannot be explained with Nakayama theory. The 7-level model consists of two upper levels and five lower levels, which account for $\pi-\pi$ polarization of both pump and probe beams in Zeeman sub levels. We compared our 7-level model with 4-level Nakayama theory for 5S$_{1/2}$ - 5P$_{1/2}$ transition line in $^{85}$Rb atoms. The results of the 7-level model calculation agree well the saturation absorption spectra data according to laser intensities.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.4
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• pp.269-273
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• 2001

W fabricated thin film using Na$_{0.5}$K$_{0.5}$NbO$_3$ volatile material by pulsed laser deposition (PLD) and studied characterization from EM, XRD, P-E. The density and scale of droplet, which is the defect of PLD, was investigated by SEM but large droplet was not found. The degree of assemble oriented C-axis measured with X-ray diffraction suggests that this film oriented C-axis achieved by $\theta$-2$\theta$ scan and rocking curves shows good self-assemble phenomenon, finally $\phi$-scan does that all of the four directions of the lattice in film equals to those of substrate. P-E hysteresis loop shows residual remnant polarization or saturation polarization value, but it is applicable to memories.ies.