| Summary: | We investigate the enhancement of second-harmonic generation in cylindrical GaAs nanowires. Although these nanostructures confine light in two dimensions, power conversion efficiencies on the order of <inline-formula> <math display="inline"> <semantics> <mrow> <msup> <mrow> <mn>10</mn> </mrow> <mrow> <mo>−</mo> <mn>5</mn> </mrow> </msup> </mrow> </semantics> </math> </inline-formula> with a pump peak intensity of <inline-formula> <math display="inline"> <semantics> <mrow> <mo>~</mo> <mn>1</mn> <mo> </mo> <mi>GW</mi> <mo>/</mo> <msup> <mrow> <mi>cm</mi> </mrow> <mn>2</mn> </msup> </mrow> </semantics> </math> </inline-formula> are possible if the pump and the second-harmonic fields are coupled to the Mie-type resonances of the nanowire. We identify a large range of nanowire radii in which a double-resonance condition, i.e., both the pump and the second-harmonic fields excite normal modes of the nanowire, induces a high-quality-factor peak of conversion efficiency. We show that second-harmonic light can be scattered with large efficiency even if the second-harmonic photon energy is larger than 1.42 eV, i.e., the electronic bandgap of GaAs, above which the material is considered opaque. Finally, we evaluate the efficiency of one-photon absorption of second-harmonic light and find that resonant GaAs nanowires absorb second-harmonic light in the near-field region almost at the same rate at which they radiate second-harmonic light in the far-field region.
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