Achromatic terahertz quarter-wave retarder in reflection mode

摘要

A compact achromatic quarter-wave retarder (QWR) operating in reflection mode is designed for using in terahertz region. It is a composite device utilizing form birefringence and Fabry-Perot (FP) interference. Under illumination of plane waves with incidence angle of 45°, from 1.8 THz to 2.8 THz, the QWR achieved only ±2° variation around 90° phase retardation, enlarging the working bandwidth of ordinary QWR greatly. An analytical model combining transmission-line (TL) theory with effective medium theory (EMT) is presented and results agree well with the time-consuming numerical calculation. The 38 μm thick construction is simple and easy for fabrication by the existing lithographic technique and a promising application in terahertz or other frequency region is believed.