超薄金属膜在太赫兹波段的光学特性研究

Study on the Optical Properties of Ultra-Thin Metal Films in the THz Band

超薄金属膜在太赫兹波段的探测器、反射镜、波导器件以及太赫兹量子级联激光器中得到了广泛应用。超薄金属膜的光学常数不仅是这些器件设计中不可缺少的参数,而且是开发新型光电材料的一个重要依据。文章运用太赫兹差分时域光谱技术对超薄金属铬、镍和钛膜的光学特性研究,获得其在太赫兹波段的折射率和消光系数,并根据菲涅尔公式计算入射介质为高阻GaAs时,GaAs/Metal界面的反射谱,三种金属在0.3～1.5THz的波段范围内的平均反射率均超过80%。研究超薄金属膜在太赫兹波段的反射特性,为设计性能优良的太赫兹辐射源、探测器及太赫兹光学元件奠定基础。

Thin metal films are good candidates of terahertz detectors,reflectors,waveguides and terahertz quantum-cascade lasers（THz-QCLs）.The optical parameter is the basis not only for designing the THz components but also for developing novel optoelectronic materials.In the present paper,the complex refractive indices of the ultra-thin metal（Cr,Ni and Ti） films in the THz band were obtained by the THz differential time-domain spectroscopy.The reflection spectra of the GaAs/metals interface were calculated according to the Fresnel formula.The mean reflectance of 25 nm Cr,Ni and Ti are over 80% from 0.3 to 1.5 THz.The results show that ultra-thin metal films can be used for reflectors as well as the electrodes in the THz band.