Active terahertz directional coupler based on phase transition photonic crystals

A phase transition photonic crystals (PhC) based silicon column arrays with VO2 coating have been proposed and fabricated, which can be actively converted between PhC directional coupler and metallic PhC waveguide by the thermal means to form a switchable directional coupler. The bandgap and transmission properties of this device have been investigated by the numerical simulation. With the changes of temperature, this device exhibits three different modulation and coupling effects. The direct output port shows the two opposite intensity modulation processes, of which transmissions decrease from dielectric PhC coupling state to the loss state and then increase from the loss to the metallic PhC waveguide state; the coupling port realizes another intensity modulation from the coupling state to non-coupling state. This device can realize switching, modulation, actively splitting and routing functions in the future's THz applications.