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Active modulation of optical leaky wave antenna by vanadium dioxide corrugations

Active tunability of optical leaky wave antenna is highly desired to enable greater control on light-matter interaction, sensing, and communication. Phase-changing materials can be integrated in optical antennas to enable such tunability. Among the phase-changing materials, vanadium dioxide (VO2) is the most useful as it shows the semiconductor to metal transition (68°C) very close to the room temperature. The phase transition in VO2 can be commonly induced by optical pulses or electrical joule heating. VO2 exhibits significant temperature-dependent electrical and optical coefficients even outside of the transition temperature making it suitable for both - fine and coarse tuning of the properties of optical devices depending on the temperature bias. In this work, we study optical leaky wave antenna consisting of a silicon nitride waveguide with periodic VO2 nanowire perturbations. We present the numerical analysis of different arrangements of the periodic perturbations. The antenna operates by the coupling between the evanescent mode of the waveguide and the nanowires. We show that, by selective joule heating of individual nanowires we can tune the optical property of corrugations and enable wider tuning range and higher degree of control on the radiated beam. We also include a comparative study to show tunability and performance of the antenna with different phase-changing materials like vanadium pentoxide (V2O5) and germanium-antimony-tellurium (GST). We show that, around the phase transition temperature of VO2, the directive gain of the antenna can be modulated by up to 25 dB and the radiation peak position can be tuned by up to 2.3°.