Abstract
Abstract Deflection, a basic functionality of wavefront manipulation is usually associated with the phase-gradient metasurfaces and the classical blazed gratings. We numerically and experimentally demonstrate an unusually wideband and simultaneously wide-angle deflection achieved at near-infrared in reflection mode for a periodic (nongradient), ultrathin meta-array comprising only one silicon nanorod (Mie resonator) per period. It occurs in the range where only the first negative diffraction order and zero order may propagate. Deflection serves as the enabler for multifunctional operation. Being designed with the main goal to obtain ultra-wideband and wide-angle deflection, the proposed meta-array is also capable in spatial filtering and wide-angle splitting. Spatial filtering of various types can be obtained in one structure by exploiting either deflection in nonzero diffraction orders, or the specular-reflection (zero-order) regime. Thus, the role of different diffraction orders is clarified. Moreover, on–off switching of deflection and related functionalities is possible by changing polarization state of the incident wave. The suggested device is simple to fabricate and only requires cost-effective materials, so it is particularly appropriate for the large-area fabrication using nanoprint lithography. Ultra-wideband wide-angle and other deflection scenarios, along with the other functionalities, are promising for applications in optical communications, laser optics, sensing, detection, and imaging.
Highlights
Anomalous refraction and deflection belong to the main scenarios of wavefront manipulation [1,2,3]
The reflective meta-array comprising dielectric nanorods of rectangular cross section has been designed with the main goal to obtain ultra-wideband and simultaneously wideangle wave deflection for the diffraction order m = −1 in case of transverse-electric (TE) polarization, i.e., when the electric field vector of the incident wave is parallel to the axes of the nanorods
It is distinguished from the mechanism reported for metal gratings [30] because surface plasmons are not expected to be a critical contributor to the resulting functionality of our meta-array and the back-side reflector is the only component of it, which is made of a metal
Summary
Anomalous refraction and deflection belong to the main scenarios of wavefront manipulation [1,2,3]. It is interesting that one nanorod per period can be sufficient to obtain wideband and simultaneously wide-angle deflection in reflection mode, as has been numerically demonstrated for dielectric circular rod [28] and rectangular rod [29] meta-arrays, as well as for all-metal gratings [30]. We numerically and experimentally study a periodic meta-array based on Si nanorods working as Mie resonators, which yields an unusually wideband and wide-angle deflection at near-infrared. The effect of polarization state of the incident wave on the possible on–off switching of the abovementioned functionalities will be discussed All these features together with the ease of fabrication indicate that the proposed device is interesting for the practical scenarios of wavefront manipulation
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