Mode changes of surface wave on the interface between dielectric rod and microwave plasma with increasing plasma density

A surface-wave plasma source with a cylindrical dielectric waveguide has been developed in our laboratory. A Teflon rod was used as waveguide where the microwave could excite the plasma around it. The transmitting modes of the surface wave on the interface between a dielectric rod and plasma changed with increasing microwave power. It was observed that the cutoff frequency of the surface wave decreased with the increase of the plasma density. And the transmitting modes of the surface wave changed from HE11 mode under no plasma or low plasma density to the degenerate mode of TM01 and TE01 with plasma density 8.9 × 1011 cm−3.