A surface wave plasma (SWP) source is described. The SWP source comprises an electromagnetic (EM) wave launcher configured to couple EM energy in a desired EM wave mode to a plasma by generating a surface wave on a plasma surface of the EM wave launcher adjacent the plasma. The EM wave launcher comprises a slot antenna having at least one slot. The SWP source further comprises a first recess configuration and a second recess configuration formed in the plasma surface, wherein at least one first recess of the first recess configuration differs in size and/or shape from at least one second recess of the second recess configurations. A power coupling system is coupled to the EM wave launcher and configured to provide the EM energy to the EM wave launcher for forming the plasma.