Three-Species Plasma-Neutral Modeling of THz Breakdown for Passive Plasma-Based Photonic Crystal Devices

Abstract

Plasma photonic crystals (PPCs) have the potential to significantly expand the capabilities of current millimeter wave filtering and switching technologies by providing high speed (μs) control of energy band-gap/pass characteristics in the GHz through low THz range. Furthermore, dielectric photonic crystals can be functionalized with self-initiated plasmas in resonant defects to provide passive power modulation. Constructing experimental devices in the low THz range is challenging, requiring plasma densities on the order of 10 22 m -3 , and sub-millimeter device characteristic lengths. Drift-diffusion models typically used in low temperature and process plasma simulations rely on reaction rate and transport coefficients calculated by Boltzmann solvers that assume low ionization fractions (<10 -5 ), and steady-state electric fields and electron densities. Ad hoc extensions to temporally and spatially varying fields must be made. Exploring computationally tractable alternative methods for high-density and high-ionization-fraction reacting plasma-neutral mixtures is therefore strongly motivated. In this work, an existing three-species (electron-ion-neutral atom) 5-moment model developed by Meier and Shumlak [ Physics of Plasmas , 19, 7, (2012)] is extended to include electron-neutral relative velocity in reaction rates in order to capture electrostatic and AC breakdown. Initial results and model validation for a THz argon plasma are presented.