Directive emissions from subwavelength metamaterial-based cavities

We use experiment and theory to demonstrate a mechanism for directive emissions, which involves a double-plate resonance cavity made with metamaterials. In contrast to other mechanisms employing Fabry-Pérot cavities, photonic crystals, or zero index materials, our system is significantly thinner than the working wavelength and requires a smaller lateral size. We show the physics to be governed by subwavelength resonance modes unique to such metamaterial-based cavities.