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

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.