Electric-field-resolved near-infrared microscopy

Abstract

Access to the complete spatiotemporal response of matter due to structured light requires field sampling techniques with sub-wavelength resolution in time and space. We demonstrate spatially resolved electro-optic sampling of near-infrared waveforms, providing a versatile platform for the direct measurement of electric field dynamics produced by photonic devices and sub-wavelength structures both in the far and near fields. This approach offers high-resolution, time- or frequency-resolved imaging by encoding a broadband signal into a narrowband blueshifted image, lifting the resolution limits imposed by both chromatic aberration and diffraction. Specifically, measuring the field of a near-infrared laser with a broadband sampling laser, we achieve 1.2 µm resolution in space and 2.2 fs resolution in time. This provides an essential diagnostic for complete spatiotemporal control of light with metasurface components, demonstrated via a metalens as well as a meta-axicon that forms broadband, ultrashort, truncated Bessel beams in the near infrared. Finally, we demonstrate the electric field dynamics of locally enhanced hot spots with sub-wavelength dimensions, recording the full temporal evolution of the electric field at each point in the image simultaneously. The imaging modality opens a path toward hyperspectral microscopy with simultaneous sub-wavelength resolution and wide-field imaging capability.