兆赫波波段金屬網狀濾波器之研究

Abstract

本論文著重在研究兆赫波（1 THz∼10 THz）通過各種薄金屬網狀結構的穿透率，利用簡易的製程與簡單的設計概念，得到濾波效果佳之濾波器。 我們首先研究的濾波器結構係將蒸鍍於矽基板上之薄金屬蝕刻出以正方形陣列排列之十字狀的洞。藉由改變洞的透光面積、長寬比與破壞對稱性等等，從中觀察到透光面積介於20％到40％可得到較佳穿透率之濾波器；且可藉由調整長寬比及破壞洞與陣列的對稱性來改變半高寬；而改變週期或變換不同折射率之基板可用來控制濾波器的峰值波長。 接著我們將上述結構所得到之結果運用在六角對稱結構之中，將薄金屬蝕刻出雪花狀的洞，以此設計成功製作出穿透率接近100％之薄金屬網狀濾波器。而此結構使我們得以串聯使用兩個相同濾波器，除可降低濾波頻帶外之穿透率，亦能保有高於90％的穿透峰值，提升濾波器之濾波效果。

In this thesis, we examine the transmittance of thin metal meshes in the terahertz region (1 THz∼10 THz). By using standard litho processes and applying simple design concepts, we can fabricate THz filters with high performance. The metal on a substrate is etched with square array of cross holes. We find that filters with 20∼40％ pervious area have optimal transmittance. We can adjust the bandwidth of the filters by changing the aspect ratio of the holes and by reducing the symmetry of our structures. In addition, we can adjust the main peak frequency by changing the period of the hole array or by changing the substrate material. By applying the above results to the hexagonal array of snowflake holes, we can design the filters with transmittance close to 100％. When two filters of the same structure are placed in series, they can reduce the stop-band transmittance while keeping the main peak transmittance higher than 90％.