Figure 1 | Working principle of the nonlinear nonlocal metasurface. (IMAGE)
Caption
Figure 1 | Working principle of the nonlinear nonlocal metasurface.(a) A nonlocal metasurface is excited from below by circularly polarized light at the pump frequency, ωp . The metasurface has a locally tailored resonant polarization, depicted by the colored arrows above the metasurface. The colors of the array track the phase of the coupling process, inherited from the polarization-dependent phase of the incident circular polarization. As a result, a nonlocal mode, characterized by the field component Ex , is excited within the metasurface with a resonantly enhanced amplitude and a spatial gradient of phase along the x direction. (b) The third-harmonic generation process in the metasurface is characterized by the quantity as the equation shown in (b) , which inherits three times the phase gradient from the pump. The resulting nonlinear polarization currents, denoted by colored arrows, scatter the third harmonic to the far field in a direction dictated by the engineered phase gradient, with two diffraction orders in the y direction due to the superwavelength periodicity of the metasurface.
Credit
Andrea Alù et al.
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