A Design of broadband THz antireflection coating

Hsin Yu Yao^1*, Zih Yu Chen¹, Tsun Hsu Chang¹

¹Department of physics, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Hsin Yu Yao, email:s5te633v@hotmail.com

We design a ten-layer anti-reflection coating for silicon wafer in the THz region. Simple design guideline based on binomial multi-section transformer is developed to determine the thicknesses of matching layers and the refractive index profile. Those layers are proposed to be realized by doping the high-index (silicon) or low-index (air pore) subwavelength-size particles into the host polymer layers (HDPE). The THz transmission power from a 375-um-thick silicon double-side integrated with the designed AR coating achieves 95.00% for 0.203 THz to 0.919 THz (127.63% bandwidth) under normal incidence. Besides, this design not only works for a TE-polarized wave but also for a TM-polarized wave incident from an arbitrary angle below 50^o. The sensitivity analysis suggests that such coating exhibits strong resistance to both the index and thickness changes of all matching layers, facilitating an easier fabrication procedure. These features imply that the present design might have multiple further applications in THz windows, THz filters, THz lenses, and semiconductor source devices.

Keywords: Antireflection coatings, Multilayer design, Subwavelength structures, Thin film devices