Abstract
Backward phase matching, which describes counterpropagating fundamental and harmonic waves in a negative‐index medium, is one of the most intriguing phenomena in nonlinear metamaterials. Predicted theoretically decades ago, however, it is still a challenging task to be applied for efficient second harmonic (SH) generation in a nonlinear metamaterial with ultrathin geometry and ultralow loss. Here, a negative‐index spoof plasmonic metamaterial is reported, which is composed of an ultrathin symmetrical corrugated metallic strips loaded with nonlinear active devices. The simulated and measured power spectra and surface near‐field distributions show that a peak SH signal can be generated at the backward phase‐matched frequency point in a 120° curved surface with high efficiency, thanks to the ultrathin flexible geometry, significant confinement effect, and large propagation length of the spoof surface plasmons. The results open new technological challenges from nano‐ and micro‐nonlinear photonics to science and engineering of compact, broadband, and efficient frequency‐mixing metamaterials and electromagnetic devices.
Highlights
Backward phase matching, which describes counterpropagating in those nonlinear processes mostly limited to subwavelength interaction lengths fundamental and harmonic waves in a negative-index medium, is one of to avoid the destructive effects of phase the most intriguing phenomena in nonlinear metamaterials
One of the most intriguing phenomena in nonlinear plasmonic metamaterial is reported, which is composed of an ultrathin metamaterials, has attracted surging symmetrical corrugated metallic strips loaded with nonlinear active devices
Introduction and μ = μ0, μ0 is the permeability in free space) ones to realize highly efficient backward SHG? Lately, a new method based on Nonlinear optics is of tremendous importance to modern, light- a bulk metal–insulator–metal plasmonic waveguide, which is a based technology.[1]
Summary
To experimentally confirm the backward phase matching for SHG in the negative-index nonlinear spoof plasmonic metamaterial, we fabricate a sample with 40 nonlinear unit cells shown in Figure 3a, whose geometry parameters and the varactor loading scheme are the same as that listed in the simulation scenarios in Figures 1 and 2. To experimentally confirm the backward phase matching for SHG in the negative-index nonlinear spoof plasmonic metamaterial, we fabricate a sample with 40 nonlinear unit cells shown, whose geometry parameters and the varactor loading scheme are the same as that listed in the simulation scenarios in Figures 1 and 2. To facilitate inject and measure the FF and SH waves, a coplanar waveguide of length L1 = 40 mm (L3 = L1 = 40 mm) with 50 Ω port impedance is employed. It is worth noting that the dispersion relation of the nonlinear spoof plasmonic metamaterial is insensitive to the capacitance value of the varactor (details in Figure S2a,b, Supporting Information), which implies that the backward phase matching for SHG can be achieved by optimizing
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