As one type of non-diffraction beams, Airy beams have received enormous interest due to the unique diffraction-free, self-accelerating, and self-healing properties.Airy beams have found a wide range of applications including optical micromanipulation, microscopy, micromachining of curved profiles. Conventional protocols for generating Airy beams rely on the utilization of bulky optical elements, which is against high-density optical integration on a chip.Metasurfaceshaveprovided a compact method to generate Airy beams, but the reported Airy beam generators suffer from the issue of narrow bandwidthasthey typically rely on resonance principles. In addition, the inherent ohmic loss of metal will remarkably deteriorate the efficiency of the Airy beams around near-infrared band if metasurfaces with metal are involved.
In order to address the above-mentioned issues, Prof. Lin Chen's group from Optoelectronic Devices and Integration Division of Wuhan National Lab for Optoelectronics, proposes a scheme for the ultra-broadband high-efficiency generation of Airy beams based on all-silicon metasurfaces. Adjusting the structural parameters of nanopillars, the building blocks can maintain high birefringence,and low lossover a wide spectral range.The relationship between the normalized amplitude, relative phase distributions of the transmissive electromagnetic waves and orientation anglesof nanopillars has been derived.Then,the local amplitude and phase distributions of the transmitted electromagnetic waves passing through such silicon nanopillars can be well adjusted to follow the Airy function within a wide spectral range by changing orientation angles of the nanopillars.High efficiency Airy beams were numerically and experimentally verified over an ultra-wide spectral band ranging from 1.1 to 1.7 µm with the maximum efficiency of 78% in simulaiton, which is the widest operation bandwidth achieved for Airy beams in the optical domain with metasurfaces to date. The proposed scheme can stimulate the design of high efficiency devices with the simultaneous requirement of controlling the amplitude and phase distributions over a wide spectral band.
This work, titled as "Ultra-Broadband High-Efficiency Airy Optical Beams Generated with All-Silicon Metasurfaces", has been recently published in Advanced Optical Materials.
Address:
https://onlinelibrary.wiley.com/doi/full/10.1002/adom.202001284
Figure 1. Schematic view of the high-efficiency broadband Airy optical beam generator.
Figure 2. Simulated (a-d) and experimental (e-h) demonstration of Airy beam generation.
