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Electronically Controlled Multi-color Optical Shutter with Metallic Nanostructure

Electronically Controlled Multi-color Optical Shutter with Metallic Nanostructure
Translated Title
전기적으로 색을 조절 가능한 금속 나노구조체 기반의 광학 셔터
Lee, Young Jin
DGIST Authors
Lee, Young Jin; Jang, Jae Eun; Cho, Chang Hee
Jang, Jae Eun
Cho, Chang Hee
Issue Date
Available Date
Degree Date
2017. 2
Electrically Tunable Multi-color Optical FilterNanohole ArraysLiquid Crystal능동적인 컬러필터플라즈모닉 구조체편광셔터
Electrically tunable multi-color optical filter structure has been studied employing asymmetrical nanohole array design and a twisted nematic (TN) mode of liquid crystal (LC). Recently, some researches have been reported to get various color states in one unit cell structure, since it can be one of the most important solution for ultra-high integration density of some opto-electrical devices such as a semiconductor based image sensor or a display device. Nanometer level size hole arrays on metal film have shown extraordinary phenomenon, filtering effect on visible light due to surface plasmonic effect mainly. The filtering color can be changed by the control of environmental factors such as a refractive index, a dielectric constant or incident polarization direction. However, most of these control principle is not electrical methods, but the change of material property or mechanical principle, so that it is hard to apply this structure to various opto-electrical devices. In this thesis, in order to solve these limitations, 2-dimensional (2D) asymmetric nanohole array design with electrical polarization rotator function employing a twisted nematic (TN) mode of liquid crystal (LC) has been suggested. Nanohole arrays having different structure factors of x and y axis were fabricated on aluminum film. This asymmetric nanohole array design allows to get two different principle colors and mixed states with modulation of incident light polarization, even if it is a structural fixed design. The polarization state is tuned electrically by TN-LC structure combined with the asymmetrically designed nanohole layer. The color tuning shift is larger than 100nm depended on the design layout of nanohole array. It is not easy to get this wide range color change by a control of refractive index of surrounding materials, generally. The functional ability as electrode of nanohole array on metal film and low driving voltage of TN cell mode can open high probability to apply to various electronic device concepts, such as dynamic display, variable information encoding, anti-counterfeiting. ⓒ 2017 DGIST
Table Of Contents
Ⅰ. INTRODUCTION 1 -- 1.1 Motivation 1 -- 1.2 Plasmonic Color Filter 1 -- 1.2.1 Surface Plasmons 1 -- 1.2.2 Plasmonic Color Filter Using Nanohole Arrays 3 -- 1.2.3 Dielectric Constant Sensitivity 4 -- 1.3 Liquid Crystal 5 -- 1.3.1 Property of Liquid Crystal 5 -- 1.3.2 Polarization Rotator Using Liquid Crystal 6 -- 1.4 Active Plasmonics Materials 7 -- 1.4.1 Liquid Crystal 8 -- 1.4.2 Polymer 9 -- 1.4.3 Photochromic Molecules 10 -- 1.4.4 Inorganic Materials 10 -- Ⅱ. EXPERIMENT DETAILS 11 -- 2.1 Concept of Active Plasmonic Color Filter 11 -- 2.1.1 Design of Plasmonic Color Filter 11 -- 2.2 Fabrication of Active Plasmonic Color FIlter 11 -- 2.2.1 Fabrication of Plasmonic Color Filter 11 -- 2.2.2 Liquid Crystal Polarization Rotator 12 -- 2.2.3 Active Color Filter with Changeable Dielectric Constant 14 -- 2.2.4 Active Color Filter with Polarization Effect 14 -- 2.3 Measurement System for Fabricated Color Filter 17 -- Ⅲ. RESULTS AND DISCUSSION 18 -- 3.1 Theoretical Studies for Nanohole Array Structure 18 -- 3.1.1 Simulation of Electric Field at the Surface of Metal 18 3.1.2 Electric Field Intensity Distributions for the Asymmetric Nanohole Arrays System 20 -- 3.1.3 Simulation of Electric Field at the ITO Electrodes Array 21 -- 3.2 Characteristics of Plasmonic Color Filter 22 -- 3.3 Characteristics of Liquid Crystal Polarization Rotator 25 -- 3.4 Characteristics of Active Color Filter with Changeable Dielectric 28 -- 3.5 Characteristics of Active Color Filter with Polarization Effect 33 -- 3.5.1 Plasmonic Color Filter on TN Polarization Rotator 33 -- 3.5.2 Plasmonic Color Filter on TN-Lateral Polarization Rotator 35 -- 3.5.3 The Effect of Alignment Layer to Color Filter 38 -- 3.5.4 Characteristics of LC Combined Color Filter 42 -- IV. CONCLUSION 49
Information and Communication Engineering
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