Figure | Conceptual illustration of Spatial Harmonic-expanded Generalized Snell’s Law (SH-GSL). (IMAGE)
Caption
Figure | Conceptual illustration of Spatial Harmonic-expanded Generalized Snell's Law (SH-GSL). a, The schematic of the metasurface for abnormal-harmonic reflection. b, The schematic of the metasurface for multi-beam splitting. c, The schematic of the metasurface for perfect multi-channel retroreflection. d, The illustration of the proposed SH-GSL for harmonics manipulation. The fundamental harmonic can be manipulated by gradient metasurfaces based on the generalized Snell’s law (d left), while high-order harmonics need to be analyzed by the Floquet period theory (d left). By combining the phase gradient (GSL) and the period property (Floquet period theory), the abnormal reflection of harmonics can be manipulated according to a deterministic Floquet-engineered momentum compensation mechanism of spatial harmonics (d middle). Furthermore, by utilizing multi-harmonics simultaneously, the multi-channel retroreflection based on multiple harmonics can be achieved (d right). The 0th harmonic is controlled by the generalized Snell’s law in the red box, the −1st harmonic is denoted as the mirror mode in the yellow box, and the other order harmonics can be manipulated by the Floquet period theory in the blue box.
Credit
Yueyi Zhang et al.
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