We perform multipolar analysis of second-harmonic generation (SHG) from gallium arsenide (GaAs) nanoantennas grown along different crystallographic directions and discuss their specifics. In particular, analysis of the nonlinear response of nanoantennas grown along the (110) axis based on the Lorentz lemma shows that such nanoantennas generate multipoles with only odd azimuthal index m. This feature of (110)-GaAs nanoantennas provides the best forward/backward directivity as compared to their (100) and (111) counterparts. Using numerical modeling we determine parameters of the cylindrical nanoantenna to achieve optical switching in the nonlinear regime by rotating the pump polarization. We then experimentally demonstrate the nonlinear switching between forward and backward SHG emissions from (110)-grown GaAs nanodisks.
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