Local Metasurface With Vertically Stacked III‐V Semiconductor Disks for Resonant Nonlinear Optics and Up‐Conversion Imaging

III‐V semiconductor metasurfaces are promising platforms for realizing sub‐wavelength‐scale frequency converters due to their superior linear and nonlinear optical properties. Here, we report strong resonant enhancement in nonlinear optical processes from a novel semiconductor metasurface consisting of arrays of vertically stacked AlGaAs disks held together by a thin GaAs stem. The metasurface supports highly localized resonances due to the excitation of hybrid anapole scattering modes among closely spaced disks within the vertical stack. Linear reflectance studies on the fabricated metasurfaces show characteristic resonance dips due to anapole‐like scattering mode which agrees with the peak in the second harmonic (SHG) and sum frequency generation (SFG). Strong resonant enhancement in SHG and SFG are achieved with intensity normalized conversion efficiencies as high as 1 × 10 −3 (1.9 × 10 −5 ) and 1.55 × 10 −4 (2.05 × 10 −5 ) cm 2 /GW under widefield (tightly focussed) excitation, respectively. The conversion efficiency numbers obtained here are comparable with some of the highest reported under pulsed excitation, despite the metasurface having significantly lower quality factor (∼20). As an application of the resonant frequency conversion process, we demonstrate widefield up‐conversion imaging by frequency converting extended object patterns imprinted on the incident beam to shorter wavelengths which are imaged using conventional silicon‐based camera with good up‐conversion image quality.