Two-Beam Coupling Effects in Nematic Liquid Crystals Doped with Carbon Nanotubes

• Main Authors: Shen-Long Yeh, 葉昇龍
• Other Authors: Wei Lee
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/31216266279631124165

碩士 === 中原大學 === 應用物理研究所 === 89 === We show by two-beam coupling experiments that nematic liquid crystals doped with carbon nanotubes exhibit photorefractive effects. We found three kinds of time-evolved two-beam coupling curves. Under some specific conditions, the photorefractive gain constant G reached ~1000 cm－1. Our results indicate that the optimal applied dc voltage occurred at 14 V, where the two-beam coupling gain constant became maximum regardless of the total beam power and the beam ratio. The two-beam coupling gain constant was increased as the beam ratio rose; the gain also became increased with increasing total beam power as long as the total power was less than 160 mW. We estimated the rise time to be ~30 s and decay time ~50 s for our samples. We speculate that photo polymerization of carbon nanotubes may have taken place under laser illumination and the polymeric species at the interface can trap charges to create the electric capacity effect, leading to prolong decay time.