High Numerical Aperture Meta-axicons
Bessel beams have attracted much attention due to their unique non-diffractive properties. Typically, zeroth order Bessel beams are generated using a conical prism (known as an axicon) or an objective paired with an annular aperture. However, the former approach has a limited numerical aperture (NA), and the latter suffers from low efficiency, since most of the incident light is blocked by the aperture. The generation of higher-order Bessel beams requires an additional phase-modulating element, which in turn adds complexity and bulkiness to the system. Researchers in the Capasso group at Harvard have overcome these problems using dielectric metasurfaces, and demonstrate meta-axicons with high NA up to 0.9 which are capable of generating Bessel beams with full-width at half-maximum. Additionally, these Bessel beams have transverse intensity profiles independent of wavelength across the entire visible spectrum. These meta-axicons can enable advanced research and have a variety of applications related to Bessel beams, including laser fabrication, imaging, and optical manipulation.
Intellectual Property Status: Patent(s) Pending