(a) SEM images of a conical metallic tip with a grating coupler on the shaft, principle of the nonlocal excitation of the tip apex and series of microscope images recorded for illumination of the tip at the four positions.^[61] (b) Schematic diagram of scanning the nanofocusing tip across a silicon step edge, SEM image of step edge, and the optical signal of a lateral scan across the step edge.^[62] (c) SEM image of an Au tip with a chirp grating coupler 20 μm away from the apex.^[63] IAC of the photoelectron current emitted from the apex. (d) Nanofocusing of a few femtosecond pulse at the tip: FROG measurement based on apex localized SHG of adiabatically nanofocused SPP, and reconstructed spectral and temporal phase (blue), intensity (red), as well as the reconstructed temporal electric field transient (green).^[64]