Studies of Optically and Electrically Controllable Fresnel Lenses in Twisted-Nematic Liquid Crystals

• Main Authors: Chien-Yu Li, 李建瑜
• Other Authors: Hui-Chen Yeh
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/72du93

碩士 === 國立高雄第一科技大學 === 電機工程研究所碩士班 === 103 === In this study, we fabricated the twisted nematic liquid crystal Fresnel lens based on the photoconductive PVK film doped with C60. The sample was irradiated with a Fresnel-patterned blue beam derived from a Sagnac interferometer, leading to an increase in the conductivity of PVK in the bright zones of the interference pattern. The director distributions of liquid crystal in the bright and dark zones differ under applied voltages because of the different effective electric fields. When a red probe beam passed through the sample, diffraction occurred so that the light waves were focused, similar to light passing through a lens. We can optically and electrically control the diffraction efficiency of the Fresnel lens by changing the intensity of the Fresnel-patterned blue beam and applied voltages to alter the effective electric fields in bright and dark regions of the interference pattern.