Broadband Generation of Airy Beams with Hyperbolic Metamaterials

The Airy beam has attracted considerable research interest owing to the intriguing diffraction-free, self-accelerating, and self-healing properties, and hence has found numerous applications in photonics. Metasurfaces provide a compact method to generate Airy beams, but the available Airy beam generators suffer from the issue of narrow bandwidth since they typically rely on resonance principles. Here, hyperbolic metamaterials (HMMs) are proposed to address this issue by taking advantage of the broadband high birefringence. By changing the orientation angle of the HMM unit, the local amplitude and phase distributions of the transmitted electromagnetic waves passing through such HMM unit can be well adjusted to follow the Airy function within a wide spectral range. The resultant microwave Airy beam generator promises an operation bandwidth from 7.2 to 9.6 GHz, while the near-infrared Airy beam generator has a working bandwidth from 1.25 to 2.40 mu m over 10% transmission efficiency. The proposed Airy beam overcomes the limitation of the customary Airy beams with the issue of narrow bandwidth and can stimulate the design of complicated optical devices with the requirement of maintaining the amplitude and phase distributions over a wide spectral band.