Gallium Phopshide Nanostructures on Transparent Substrates for Nonlinear and Ultrafast Nanophotonics

Gallium Phosphide (GaP) is a material with outstanding optical properties and a promising candidate for nanophotonic applications. Among comparable materials, it is one with the highest linear refractive indices and due to its wide and indirect bandgap, it has a lossless transparency for wavelengths longer than 450 nm. The bulk crystal was already shown to have a strong ultrafast response [1] and nanostructuring of a GaP wafer led to a record conversion efficiency in second-harmonic generation (SHG) [2] . Nevertheless, such structures are based on a high refractive index substrate and therefore no optical contrast in that direction. This prevents strong optical resonances and therefore naturally limits nonlinear efficiencies.