Ji Yun-Yun, Fan Fei, Zhang Xin, Cheng Jie-Rong, Chang Sheng-Jiang
Opt Express. 2020 Jun 8;28(12):17253-17265. doi: 10.1364/OE.392773.
Terahertz (THz) birefringence anisotropy of the polymer-dispersed liquid crystal (PDLC) doped with gold nanoparticles (Au NPs) is investigated by using terahertz time domain polarization spectroscopy. Controlled by the electric field, the change rate of refractive index for PDLC doped with Au NPs is 0.91% V as the voltage increases, smaller than the pure PDLC, which indicates that the response of the PDLC doped with Au NPs to electric field is more uniform than that of pure PDLC. Therefore, the PDLC doped with Au NPs is more suitable for tunable phase shifters. Furthermore, we found that under the high-frequency alternating electric field, the anisotropic polarization effect of PDLC will disappear to this electric field, namely polarization relaxation phenomenon. However, the results show that the PDLC doped with Au NPs can respond to an electric field with higher alternating frequencies, and the relaxation frequency of PDLC with an Au NPs concentration of 0.2 wt% was improved over two times compared with the pure PDLC and four times higher than that of the precursor mixture without ultraviolet radiation. This work has the significance for the potential applications of tunable THz liquid crystal phase and polarization devices, providing a more uniform and faster relaxation response to the operating electric field.
采用太赫兹时域偏振光谱法研究了掺杂金纳米粒子（Au NPs）的聚合物分散液晶（PDLC）的太赫兹（THz）双折射各向异性。在电场作用下，掺杂Au NPs的PDLC的折射率变化率随着电压增加为0.91%V，小于纯PDLC，这表明掺杂Au NPs的PDLC对电场的响应比纯PDLC更均匀。因此，掺杂Au NPs的PDLC更适合用于可调谐移相器。此外，我们发现，在高频交变电场下，PDLC的各向异性极化效应会对该电场消失，即极化弛豫现象。然而，结果表明，掺杂Au NPs的PDLC能够响应更高交变频率的电场，与纯PDLC相比，Au NPs浓度为0.2 wt%的PDLC的弛豫频率提高了两倍多，比未经过紫外线辐射的前驱体混合物高四倍。这项工作对于可调谐太赫兹液晶相位和偏振器件的潜在应用具有重要意义，为工作电场提供了更均匀、更快的弛豫响应。
