In the last years metasurfaces have revolutionized the field of optics, with the promise of replacing bulky optical systems and providing new functionalities by nanostructured thin films. “Flat optics” also showed its potential in the nonlinear regime, mostly in III-V semiconductors, and we recently achieved second harmonic generation with phase-front control in a nonlinear metasurface (NLMS). Today we aim to harness the full potential of NLMSs by tackling an old problem of nonlinear optics: the upconversion of infrared radiation into the silicon absorption band via sum frequency generation (SFG). By heterogeneous integration of a high-efficiency NLMS, a linear metalens and a single photon avalanche photodiode (SPAD), we will demonstrate a miniature device allowing for ultrafast detection of infrared signals with wavelength beyond the fast-detection limit of InGaAs APDs. To this end, we will address a triple challenge in design, forefront nanofabrication, and ultrafast characterization. This project will both push forward fundamental research and go beyond purely academic interest. The targeted device will provide the breakthrough of ultrafast detection of infrared radiation at 300K, spurring the transition of the young NLMS research field from fundamental research into a set of high-impact applied technologies.