Ultrafast Coherent Absorption in Diamond Metamaterials.

Diamond is introduced as a material platform for visible/near-infrared photonic metamaterials, with a nanostructured polycrystalline diamond metasurface only 170 nm thick providing an experimental demonstration of coherent light-by-light modulation at few-optical-cycle (6 fs) pulse durations. "Coherent control" of absorption in planar (subwavelengththickness) materials has emerged recently as a mechanism for highcontrast all-optical gating, with a speed of response that is limited only by the spectral width of the absorption line. It is shown here that a freestanding diamond membrane structured by focused ion beam milling can provide strong, spectrally near-flat absorption over a visible to near-infrared wavelength range that is wide enough (wider than is characteristically achievable in plasmonic metal metasurfaces) to facilitate coherent modulation of ultrashort optical pulses comprising only a few oscillations of electromagnetic field.