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, such as particles manipulation, light bullet, and curved plasma channel generation. Traditional methods to generate an Airy beam usually require a complex and bulky optical system, such as a Fourier transform lens and a spatial light modulator, which is against a high-density optical integration on a chip. 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.
Prof. Lin Chen’s group from Optoelectronic Devices and Integration Division of Wuhan National Lab for Optoelectronics, proposes a scheme for the broadband generation of Airy beams based on hyperbolic metamaterials (HMM). The building block of the HMM can always support a branch of SSP mode on both side walls. 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 relationship between the normalized amplitude, relative phase distributions of the transmissive electromagnetic waves, and the orientation angle of the HMM has been derived. Then 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, and 1.25 to 2.40 μm, 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.
This work, titled as "Broadband Generation of Airy Beams with Hyperbolic Metamaterials", has been recently published in Advanced Optical Materials. This work was supported by the National Natural Science Foundation of China (Grant Nos. 11474116, 11674118) and State Key Laboratory of Advanced Technology for Materials Synthesis and Processing (Wuhan University of Technology).
Figure 1. Schematic illustration of a hyperbolic metamaterials Airy beam generator.
Figure 2. The field intensity distributions of output fields of the sample (a) and the transmission efficiency as a function of frequency (b).
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https://onlinelibrary.wiley.com/doi/10.1002/adom.201900493
