Spin of Light Tuning of Microwave Components

Reconfigurability will be a central theme in the next generation of microwave and millimetre-wave components. Reconfigurable or tuneable microwave devices, whose electromagnetic response can be changed on the fly, enable us to reduce complexity, size, weight, power consumption, and cost. The industry standard for such agile microwave technology relies on electronic tuning. In contrast, inspired by the new advancements in spin-orbit coupling of light, we explore the use of such spin-orbit interaction to tune the electromagnetic response of a helical tape. When the incident circularly-polarized wave is of the same handedness as the helix, the helical tape behaves as a transmission line (i.e., waveguide); on the contrary, a counter-rotating circularly-polarized wave converts the helical tape into a leaky-wave antenna with a conical radiation pattern. The underlying mechanism is explained in terms of Floquet theorem. Two prototypes operating within the X band of the microwave spectrum are fabricated and measured. Numerical and experimental results are in good agreement.