  This work presents an experimental study of giant and pure optical activity
in a periodic structure consisting of twisted crosses and complementary crosses
patterned on the sides of a copper coated dielectric board. Additionally, a
multilayer system is proposed and numerically studied to broaden the
transmission bandwidth. Our results show that a dual band behavior can be
obtained due to coupling effects between the layers whilst maintaining the
dispersionless giant optical activity and negligible circular dichroism. We
theoretically study the effect of the separation between layers and its
influence on the transmission spectra.
