Electrically Thin Metasurface For Broadband Transmission Enhancement By Manipulating The Amplitude And Phase Of The Reflection Coefficients

We present a broadband and electrically thin antireflective metasurface for enhanced electromagnetic transmission in the low gigahertz range. In this design, an electrically thin sandwich structure (similar to lambda/8) is proposed and studied numerically and experimentally. The destructive interference theory is used to elucidate the designing principle, and by simply tailoring the structural geometrical parameters, the interference conditions at two resonator-spacer interfaces can be tuned to satisfy over a broad frequency range. Measurement results show that transmittance is higher than 85% over a range with a relative bandwidth of 32%, reaching 95% at the maximum, comparing with the transmittance of 65% if no such metasurface is in place. A corresponding low reflectance can also be achieved over a wide range of incidence angles for transverse electric and transverse magnetic polarizations. More importantly, we find that this type of antireflective transmission enhancement is insensitive to the choice of resonators as long as the " spacer-substrate" interface is coated by split ring resonators. It thereby eases the design for a variety of transmission enhancement applications such as nondestructive testing applications and ultrathin detectors in the future.