Reflection and phase of left-handed metamaterials at microwave frequencies

We experimentally investigated the reflection and phase of the left-handed metamaterials (LHMs) in a rectangular waveguide for the normally incident microwave. The samples are constructed by periodically arraying the copper split ring resonators (SRRs) and wires. It is found that for the LHMs with one-layered SRRs, a reflection peak with a depth of -3.3 dB (i.e. with the reflectivity of 47%) occurs in the left-handed range. The dependence of reflection phase on the frequency is different from that of the transmission phase, and the reflection phase has an inflexion at the reflection peaks. For the LHMs with three-layered SRRs, the depth of reflection peak increases with the row number, i.e. reflection is weakened, and the reflection peak has a shift with respect to the left-handed transmission peak. It is thought that the interaction between different layers of SRRs is the reason of the shift.