The invention provides a plurality of resonator subsystems. The resonator subsystems can comprise one or more resonant cavities configured to couple electromagnetic (EM) energy in a desired EM wave mode to plasma by generating resonant microwave energy in a resonant cavity adjacent the plasma. The resonator subsystem can be coupled to a process chamber using one or more interface subsystems and can comprise one or more resonant cavities, and each resonant cavity can have a plurality of plasma tuning rods coupled thereto. Some of the plasma tuning rods can be configured to couple the EM-energy from one or more of the resonant cavities to the process space within the process chamber.