Compact quarter-wave plate metasurface at 1 and 2.2 THz

We propose a very compact dual-band quarter-wave plate (QWP) which is inspired on extraordinary transmission subwavelength hole arrays. To control independently orthogonal polarizations, the original square holes are connected with vertical slits and meander lines replace their lateral straight sides. The structure is numerically analyzed and experimentally demonstrated at terahertz frequencies. The metasurface exhibits an experimental fractional bandwidth equal to 16.8% and 2.9% (52.1% and 4.3% in simulation) at 1 THz and 2.2 THz in a structure as compact as 0.13? and 0.29λ, respectively.