Microplasmas Sustained in the Sub-THz Band

Steady-state microplasma generation within a photonic crystal (PhC) produces high electron density
$(> 10^{20} \mathrm{m}^{-3})$
in argon gas. The microplasma forms in free space within a vacancy of the crystal. In this work, the PhC consists of a rectangular array of alumina rods. By removing a single rod from the array, the resulting vacancy acts as an electromagnetic resonator. Electromagnetic waves impinging on the PhC produce a strong electric field
$(> 10^{5}\mathrm{V}/\mathrm{m})$
in the vacancy that heats free electrons to form a free-floating spheroidal microplasma. The electromagnetic response of the PhC is scalable from the microwave band into the optical band, making the PhC a suitable geometry to study plasma frequency-scaling and wave interactions.