二氧化钒薄膜低温制备及其太赫兹调制特性研究

针对二氧化钒(VO2)薄膜在可调谐太赫兹功能器件中的应用,利用低温磁控溅射技术,在太赫兹和光学频段透明的BK7玻璃上制备出高质量的VO2薄膜.晶体结构和微观形貌分析显示薄膜为单相VO2单斜金红石结构,具有明显的(011)晶面择优取向,结构致密,表面平整.利用四探针技术和太赫兹时域光谱系统分析了薄膜的绝缘体-金属相变特性,发现相变过程中薄膜电阻率变化达到4个数量级,同时对太赫兹透射强度具有强烈的调制作用,调制深度高达89％.通过电学相变和太赫兹光学相变特性的对比研究,证实薄膜的电阻率突变主要与逾渗通路的形成有关,而太赫兹幅度的调制则来源于薄膜中载流子浓度的变化.该薄膜制备简单,成膜质量高,太赫兹调制性能优异,可应用于太赫兹开关和调制器等集成式太赫兹功能器件.     

基于金属孔阵列的聚酰亚胺薄膜太赫兹探测

优化设计了多种不同孔径和形状的太赫兹波段的亚波长金属孔阵列结构,结合超薄低折射率的聚酰亚胺（PI）薄膜,探索了太赫兹时域光谱技术对超薄低折射率的探测灵敏性。利用飞秒微加工技术制备了一系列亚波长金属孔阵列结构,利用太赫兹时域光谱技术测试了阵列结构的反射波谱,获得了强烈的反射共振现象。然后在亚波长金属孔阵列结构背面叠加PI薄膜,结果表明太赫兹反射峰出现了显著低频移动现象。利用这一现象,实现了低至10 m的PI薄膜的有效探测,说明亚波长金属孔阵列结构在太赫兹传感领域对检测超薄低折射率薄膜材料有极强敏感性。收稿日期:; 修订日期:     

Dual-band and polarization-insensitive terahertz absorber based on fractal Koch curves

We report the design, fabrication, and characterization of a dual-band and polarization-insensitive metamaterial ab-sorber （MA）, which consists of periodically arranged fractal Koch curves acting as the top resonator array and a metallic ground plane separated by a dielectric spacer. Compared with conventional MAs, a more compact size and multi-frequency operation are achieved by using fractal geometry as the unit cell of the MA. Both the effective medium theory and the multi- reflection interference theory are employed to investigate the underlying physical mechanism of the proposed terahertz MA, and results indicate that the latter theory is not suitable for explaining the absorption mechanism in our investigated struc-ture. Two absorption peaks are observed at 0.226 THz and 0.622 THz with absorptivities of 91.3% and 95.6% respectively and good agreements between the full-wave simulation and experimental results are achieved.     

Double Wire-Grid Terahertz Polarizer on Low-Loss Polymer Substrates

A double-wire-grid polarizer was fabricated on both sides of a low-loss polythene film by simple electroplating and photolithographic micro-processing techniques. The performances of the polarizer were measured using a terahertz time-domain spectrometer （THz-TDS）. The transmittance is more than 70% and below 2% in the parallel and perpendicular directions of the polarizer, respectively. The extinction ratio is better than 22 dB in the broad frequency range of 0.5–3 THz, which is higher than the conventional free-standing polarizer in the high frequency region.