All-Optical Ultrafast Control of Second Harmonic Generation in AlGaAs Nanopillars

Abstract

All-dielectric nanophotonics has recently raised an increasing interest because the optical response of high-permittivity dielectric nanoparticles exhibits negligible dissipative losses and strong magnetic multipole resonances [1–4] in the visible and near-IR. We recently reported a second harmonic generation (SHG) conversion efficiency higher than 10−5 at 2 = 1554 nm (pump intensity ≈ 1.6 GW/cm2; pulse width ≈ 150 fs; repetition rate = 80 MHz) in all-dielectric Al 0.18 Ga 0.82 As-on-AlOx nanodisks [5–7]. Such a remarkable efficiency is achieved thanks to the exploitation of magnetic and electric resonances emerging at coincidence with both the pump and SHG wavelength. In addition, the choice of both the pump and, consequently, the SHG (≈ 777 nm) wavelength, set below the energy of the material bandgap, allow minimizing the two-photon absorption of the pump and the re-absorption of the SHG.