Dual-band polarization conversions and optical diode based on bilayer T-shaped metamaterial

•The work achieved x-to-y / y-to-x conversions at 106 / 163 THzfor +z propagation.•The incident waves are blocked for –z propagation.•The Txy and Tyx are increased to 0.74 and 0.75 with the PCRs reach up to nearly 100%.