Role of the substrate in monolithic AlGaAs nonlinear nanoantennas

Abstract

We report the effect of the aluminum oxide substrate on the emission of monolithic AlGaAs-on-insulator nonlinear nanoantennas. By coupling nonlinear optical measurements with electron diffraction and microscopy observations, we find that the oxidation-induced stress causes negligible crystal deformation in the AlGaAs nanostructures and only plays a minor role in the polarization state of the harmonic field. This result highlights the reliability of the wet oxidation of thick AlGaAs optical substrates and further confirms the bulk χ (2) origin of second harmonic generation at 1.55 μm in these nanoantennas, paving the way for the development of AlGaAs-on-insulator monolithic metasurfaces.