Electron Density Measurements of a Thin Plasma Layer by Surface Plasmon Interferometry

We present a new method for measuring the electron density of a thin plasma layer. The method uses evanescent electromagnetic waves in plasma. We study the transmittance of transverse-magnetic electromagnetic waves incident obliquely to a thin plasma layer, and show that we can determine the electron density of the plasma layer from the measurement of the angle of wave incidence corresponding to the maximum transmittance.