• Title/Summary/Keyword: polarization force

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Investigation of Resonant Wavelength Separation in Microband-induced Fiber Gratings

  • Sohn Kyung-Rak;Shim Joon-Hwan;Kim Kwang-Taek
    • Journal of the Optical Society of Korea
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    • v.10 no.2
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    • pp.63-66
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    • 2006
  • In microband-induced fiber gratings, polarization properties and birefringence are investigated as a function of an applied line force. With the transmission curves associated with the maximum and minimum resonant wavelengths, the polarization-dependent behaviors are analyzed. By increasing the transverse line force, the resonance wavelength for an incident light polarized to the same direction of the force is blue-shifted as much as 0.69 nm/(N/cm) while that for the other polarization is insensitive. Using the resonant wavelength separation corresponding to the force variation, the transverse effective index change or modal birefringence variation is obtained. The ratio of modal birefringence versus applied line force is ${\Delta}B/{\Delta}f_x={\sim}8.38{\times}10^{-7}$.

Design of Neodymium Permanent Magnetic Core using FEM (유한요소법을 이용한 네오디움 영구자석의 코어 설계)

  • Hur, Kwan-Do;Ye, Sang-Don
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.13 no.5
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    • pp.70-75
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    • 2014
  • Permanent magnets have recently been considered as device that can be used to control the behavior of mechanical systems. Neodymium magnets, a type of permanent magnet, have been used in numerous mechanical devices. These are permanent magnets made from an alloy of neodymium, iron, and boron to form the Nd2Fe14B tetragonal crystalline structure. The magnetic selection, magnet core design and mechanical errors of the magnetic component can affect the performance of the magnetic force. In this study, the coercive force, residual induction, and the dimensions of the design parameters of the magnet core are optimized. The design parameters of magnet core are defined as the gap between the magnet and the core, the upper contact radius, and the lower thickness of the core. The force exercised on a permanent magnet in a non-uniform field is dependent on the magnetization orientation of the magnet. Non-uniformity of the polarization direction of the magnetic has been assumed to be caused by the angular error in the polarization direction. The variation in the magnetic performance is considered according to the center distance, the tilt of the magnetic components, and the polarization direction. The finite element method is used to analyze the magnetic force of an optimized cylindrical magnet.

Numerical analysis of particle behavior around a bipolar charged electret fiber (정전 섬유필터 주위의 입자포집 및 거동에 관한 수치해석적 연구)

  • An, Gang-Ho
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.21 no.11
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    • pp.1509-1517
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    • 1997
  • Charged and uncharged particle motions and collection characteristics around a bipolar charged rectangular shape electret fiber are studied numerically. Particle inertia, fluid drag, Coulomb force and polarization force are considered to predict the particle motion around the electret fiber. The effects of particle sizes, flow velocities, number of charges and polarities are also systematically investigated. For small size particles, the single fiber collection efficiency is greatly dependent on the charge polarity and the number of charges on a particle. However, particles larger than 5.mu.m do not show charging effect on collection efficiencies in the flow velocity ranges from 1.5 cm/s to 150 cm/s when the maximum charges are within +5 to -10. The results show that a strong electric field gradient at the corner of the bipolar charged fiber plays a very important role on collecting particles regardless of its charge polarity because of the polarization force. It also shows that the most penetrating particle size for a single electret fiber decreases as the flow velocity increases and the number of charges of a particle decreases.

A study for piezoelectric properties analysis of the AlN thin film by using PFM (PFM을 이용한 AlN 박막의 압전특성 분석에 관한 연구)

  • Lee, Jong-Taek;Kim, Se-Young;Shin, Hyeon-Chang;Song, Jun-Tae
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2009.06a
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    • pp.224-225
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    • 2009
  • Aluminium nitride thin film was deposited on Au electrode and Si substrate by radio frequency sputtering system. X-ray diffraction (XRD) was utilized to identify the AlN phase, and Atomic Force Microscope (AFM) was used to obtain the images of surface morphology and roughness value of AlN thin film. The result of XRD and AFM measurement showed that the AlN thin film has strong c-axs orientation and smooth surface. In order to investigate piezoelectric response and polarization properties along to the direction of electric field, PFM (Piezoresponse Force Microscope) system was used, and the images of piezoelectric response due to switching of polarization was observed by PFM.

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Characteristics of the Polarization-Dependent Holographic grating formation on Ag/As-Ge-Se-S Multi-Layer (Ag/As-Ge-Se-S 다층박막에서 편광상태에 따른 홀로그래피 격장 형성 특성)

  • Na, Sun-Woong;Lee, Jung-Tae;Yeo, Cheol-Ho;Lee, Young-Jong;Chung, Hong-Bay
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2002.04b
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    • pp.85-88
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    • 2002
  • We have carried out two-beam interference experiments to form holographic gratings on chalcogenide $Ag/As_{40}Se_{15}S_{35}Ge_{10}$ multi-layer. In this study, holographic gratings have been formed using He-Ne laser(632.8nm) under different polarization combinations(intensity polarization holography, phase polarization holography). The diffraction efficiency was obtained by +1st order intensity and formed grating structure was investigated using atomic force microscopy.

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Splitting of Surface Plasmon Resonance Peaks Under TE- and TM-polarized Illumination

  • Yoon, Su-Jin;Hwang, Jeongwoo;Lee, Myeong-Ju;Kang, Sang-Woo;Kim, Jong-Su;Ku, Zahyun;Urbas, Augustine;Lee, Sang Jun
    • Proceedings of the Korean Vacuum Society Conference
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    • 2014.02a
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    • pp.296-296
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    • 2014
  • We investigate experimentally and theoretically the splitting of surface plasmon (SP) resonance peaks under TE- and TM-polarized illumination. The SP structure at infrared wavelength is fabricated with a 2-dimensional square periodic array of circular holes penetrating through Au (gold) film. In brief, the processing steps to fabricate the SP structure are as follows. (i) A standard optical lithography was performed to produce to a periodic array of photoresist (PR) circular cylinders. (ii) After the PR pattern, e-beam evaporation was used to deposit a 50-nm thick layer of Au. (iii) A lift-off processing with acetone to remove the PR layer, leading to final structure (pitch, $p=2.2{\mu}m$; aperture size, $d=1.1{\mu}m$) as shown in Fig. 1(a). The transmission is measured using a Nicolet Fourier-transform infrared spectroscopy (FTIR) at the incident angle from $0^{\circ}$ to $36^{\circ}$ with a step of $4^{\circ}$ both in TE and TM polarization. Measured first and second order SP resonances at interface between Au and GaAs exhibit the splitting into two branches under TM-polarized light as shown in Fig. 1(b). However, as the incidence angle under TE polarization is increased, the $1^{st}$ order SP resonance peak blue-shifts slightly while the splitting of $2^{nd}$ order SP resonance peak tends to be larger (not shown here). For the purpose of understanding our experimental results qualitatively, SP resonance peak wavelengths can be calculated from momentum matching condition (black circle depicted in Fig. 2(b)), $k_{sp}=k_{\parallel}{\pm}iG_x{\pm}jG_y$, where $k_{sp}$ is the SP wavevector, $k_{\parallel}$ is the in-plane component of incident light wavevector, i and j are SP coupling order, and G is the grating momentum wavevector. Moreover, for better understanding we performed 3D full field electromagnetic simulations of SP structure using a finite integration technique (CST Microwave Studio). Fig. 1(b) shows an excellent agreement between the experimental, calculated and CST-simulated splitting of SP resonance peaks with various incidence angles under TM-polarized illumination (TE results are not shown here). The simulated z-component electric field (Ez) distribution at incident angle, $4^{\circ}$ and $16^{\circ}$ under TM polarization and at the corresponding SP resonance wavelength is shown in Fig. 1(c). The analysis and comparison of theoretical results with experiment indicates a good agreement of the splitting behavior of the surface plasmon resonance modes at oblique incidence both in TE and TM polarization.

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Characteristics of Holographic Diffraction Grating Formation on $AS_{40}Se_{15}S_{35}Ge_{10}$ Thin Film with the Polarization State of Recording Beam (기록빔의 편광상태에 따른 $AS_{40}Se_{15}S_{35}Ge_{10}$ 박막에서 홀로그래피 회절격자형성 특성)

  • Park, Jeong-Il;Chung, Hong-Bay
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.9
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    • pp.423-428
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    • 2006
  • We have been carried out the two-beam interference method to form the diffraction grating on chalcogenide $AS_{40}Se_{15}S_{35}Ge_{10}$ thin films for Holography Data Storage (HDS). In the present work, we have been formed holographic diffraction gratings using He-Ne laser (632.8nm) under different Polarization state combinations (intensity polarization holography, phase polarization holography). It was obtained the diffraction grating efficiency by 11st order intensity and investigated the formed grating structure using Atomic Force Microscopy (AFM). As the results, it is shown that the diffraction efficiency of (P: P) polarized recording was maximum 2.4% and we found that its value was rather higher than that of other-polarized recordings. From the results, it is confirmed that the efficient holographic grating formation on amorphous chalcogenide $AS_{40}Se_{15}S_{35}Ge_{10}$ films depend on both the spatial variation of intensity and the polarization state of the incident field pattern.

Observation of Domain Structure and Polarization Switching in (001)-oriented Pb(Mg1/3Nb2/3)O3-x%PbTiO3 Single Crystals by Scanning Force Microscope (주사 힘 현미경에 의한 (001) Pb(Mg1/3Nb2/3)O3-x%PbTiO3 단결정의 도메인 구조 및 분극 스위칭 관찰)

  • Lee, Eun-Gu
    • Journal of the Korean Ceramic Society
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    • v.47 no.4
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    • pp.333-337
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    • 2010
  • Domain structure and polarization switching in (001)-oriented $Pb(Mg_{1/3}Nb_{2/3})O_3-x%PbTiO_3$ (PMN-x%PT) crystals for x=20 and 35at% have been investigated in-situ by scanning force microscope (SFM) in a piezoresponse mode under a step DC electrical voltage. In the initial annealed condition, polar nano domains (PND) and domain striations oriented along {110} were observed in x=20 and x=35, respectively. For x=20, domain switching occurs by heterogeneous nucleation, where nucleation is not confined in the vicinity of domain boundaries, but rather can occur throughout the crystal volume. However, for x=35, domain switching tends to be preferentially initiated near pre-existing twin boundaries. With increasing the applying voltage, the nuclei density increased and assembled into {110} striations, indicating a stress-accommodated domain growth process. At higher voltage, nucleation occurs heterogeneously throughout the crystal volume.

Ferroelectricity of Bi-doped ZnO Films Probed by Scanning Probe Microscopy

  • Ben, Chu Van;Lee, Ju-Won;Kim, Jung-Hoon;Yang, Woo-Chul
    • Proceedings of the Korean Vacuum Society Conference
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    • 2012.02a
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    • pp.323-323
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    • 2012
  • We present ferroelectricity of Bi-doped ZnO film probed by piezoresponse force microscopy (PFM), which is one of the Scanning Probe Microscopy techniques. Perovskite ferroelectrics are limited to integration of devices into semiconductor microcircuitry due to hard adjusting their lattice structure to the semiconductor materials. Transition metal doped ZnO film is one of the candidate materials for replacing the perovskite ferroelectrics. In this study, ferroelectric characteristics of the Bi-doped ZnO grown by pulsed laser deposition were probed by PFM. The polarization switching and patterning of the ZnO films were performed by applying DC bias voltage between the AFM tips and the films with varying voltages and polarity. The PFM contrast before and after patterning showed clearly polarization switching for a specific concentration of Bi atoms. In addition, the patterned regions with nanoscale show clearly the local piezoresponse hysteresis loop. The spontaneous polarization of the ZnO film is estimated from the local piezoresponse based on the comparison with LiNbO3 single crystals.

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Electrorheological effect on the dispersive system consisting of polarizable fine powder/dielectric oil (분극성을 갖는 미세 입자/유전유체 분산계에서의 전기유변효과)

  • Kim, Sang-Guk;Choe, Yun-Dae
    • Korean Journal of Materials Research
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    • v.3 no.2
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    • pp.185-192
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    • 1993
  • Abstract Electrorheological effect on the dispersive system of polarizable fine powder/dielectric oil has been investigated. ER effect was explained divided into following 3 mechanisms; (1) surface conductance, (2) bulk conductance, and (3) induced polarization. Mathematical model which predicts the interactive force between two fine particles in the electrorheological fluid has been introduced based on the induced polarization mechanism. This model may provide guide to select materials for strong ER effect. The attractive force between two particles was calculated using the above model for the selected 7 materials such as ceramics, ferrites, polymers etc. From the calculation result, it was found that the ceramics and ferrites are good materials which show a strong ER effect.

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