Microwave propagation along nonuniform plasma column as surface plasmon

Formation and propagation of surface plasmons (SPs) of microwaves (MWs) along a dense non-uniform plasma column were investigated by employing the finite-difference time-domain method and evidenced by experiment of argon helicon plasma. The effects of plasma density, incident frequency, and radius of plasma column on the SP features were discussed. Results showed that when the MW frequency and the density distribution of plasma column satisfy suitable conditions, SPs can be excited on the surface of a uniform plasma column when the frequency is 2-5 times of the MW, while inside a nonuniform plasma column when the plasma frequency is only a little higher (about 5%-20%) than the MW. The SP wavelength depends on the plasma density for a given incident MW frequency. The forward scatter MW field will be enhanced significantly when SP appears along the nonuniform plasma column.