  In an expansion of a previous study [1], we apply inverse design methods to
produce two-dimensional plasma metamaterial devices with realistic plasma
elements which incorporate quartz envelopes, collisionality (loss), non-uniform
density profiles, and resistance to experimental error/perturbation.
Backpropagated finite difference frequency domain simulations are used to
design waveguides and demultiplexers operating under the transverse magnetic
polarization. Optimal devices with realistic elements are compared to previous
devices with idealized elements, and several parameter initialization schemes
for the optimization algorithm are explored. Demultiplexing and waveguiding are
demonstrated for microwave-regime devices composed of plasma elements with
reasonable space-averaged plasma frequencies ~10 GHz and a collision frequency
~1 GHz, allowing for future in-situ training and experimental realization of
these designs.
