All-dielectric integration of dielectric resonator antenna and photonic crystal waveguide

Two-dimensional photonic crystal waveguides can support guided modes with low loss. Interfacing such a guided mode with free-space propagation modes is crucial for photonic integrated circuits. Here we propose a dielectric resonator antenna (DRA) fully integrated with a photonic crystal waveguide for endfire radiation. High radiation efficiency can be achieved from the DRA that relies on oscillating displacement currents in a low-loss dielectric material. The antenna is designed to operate at a high-order resonance for high gain. The reflection loss at the interface between the two components is minimized via a matching air hole, the mechanism of which is qualitatively described via temporal coupled-mode theory. As a proof of concept, the all-dielectric integrated structure is realized on a single intrinsic silicon wafer to operate at terahertz frequencies. The antenna footprint is only about one square operational wavelength. The experimental validation confirms the maximum gain of over 10.6 dBi with 3-dB angular beam widths of 29.0 degrees and 45.7 degrees in orthogonal dimensions. The impedance bandwidth obtained from simulation is 6%, spanning 311 to 331 GHz. Given a suitable low-loss dielectric material, this all-dielectric structure holds potential for scaling to infrared and visible light frequencies.