Compact circular polarizer based on chiral twisted double split-ring resonator

A compact circular polarizer is presented, which is based on a twisted double split-ring resonator (DSRR). The bottom DSRR is rotated 90 degrees with respect to the top one. When the structure is illuminated by a normally incident linearly polarized wave, the two linear components of the transmitted wave have nearly equal amplitudes and 90 degrees (-90 degrees) phase difference around the resonant frequency. This means that the transmitted wave with left-handed circular polarization is much larger (smaller) than the one with right-handed circular polarization. The electric fields and currents on the structure are analyzed to illustrate this phenomenon. The size of each unit cell in this structure is extremely small compared with the wavelength in all three dimensions. Both simulations and measurements verify our design at microwave frequencies. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794940]