Abstract-The dependence of reflectivity on inhomogeneous plasma density for one dimensional plasma photonic crystal is presented. The exponential varying and linear varying plasma density profiles have been chosen in such a way that the volume average permittivity remains constant. The transfer matrix method is used to derive the dispersion relation and reflectivity of the proposed structures by employing the continuity conditions of electric fields and its derivatives on the interface. The exponential varying plasma density profile gives high reflectivity than the linear varying plasma density profile in all considered cases. Also the exponential varying plasma density profile shows perfect reflection in considered volume average permittivity. This profile may be used in sensor applications or in plasma functional devices.

The time evolution of backscattered and sidescattered microwaves from a plane conductor covered by a pulsed-plasma column has been studied; transmitted signals along the axial and transverse directions of the column have also been studied. The incident microwaves are at a cw power level varying from a few milliwatts to a few watts. The cw nature of the signal makes it possible to observe the fine structure in the time evolution of the interactions. The plasma is generated by an array of plasma guns embedded in the conducting plate. The plasma density has a gradient in the axial direction and contains regions of subcritical and supercritical plasma density. Reductions in the backscattered radiation down to the lowest measurable levels with available equipment are observed for durations that are an order of magnitude longer than the duration of the current pulse that generated the plasma. Variations caused by changes in the charging potential on the plasma gun capacitor bank, the pressure of the background gas, and the frequency and power level of the incident microwaves are reported. The attenuation in the backscattered radiation decreases with increasing pressure, especially at lower charging potentials. There is a close correlation between the timing and location of sidescattered signals and the transition of the critical density layer across the axial position of the detectors for the scattered signal. The amplitude of the scattered signal was also measured. Estimates have been made for the percentage of incident power accounted for by scattering. Models are discussed for absorption of microwaves in the plasma.

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Abstract-The effect of graded permittivity profiles, filling factor and incident angles on the dispersion characteristics and reflectivity of binary one dimensional plasma photonic crystals having linearly graded dielectric materials are investigated by using the transfer matrix method. It is observed that position, width of band gap and high reflectance range can be improvised to desired level by proper choice of filling factor and graded permittivity index. The incident angle is found to affect the band gap and high reflectance range. Our analysis also shows that this plasma photonic crystal may be used for sensing applications.