Ultrafast holographic chiroptical microscopy

Although spatiotemporal resolution is desirable for studies on transport and disorder in various materials, there is currently no technique for imaging ultrafast chiroptical responses over large fields of view. Here we report widefield ultrafast chiroptical microscopy using multiplexed off-axis holography with femtosecond pulses. By encoding the horizontal and vertical polarization components of the probe pulse at different positions in Fourier space, we fully retrieve the polarization ellipse for each pixel of a widefield image. This enables the reconstruction of transient complex-valued chiroptical images, which consist of optical rotatory dispersion and circular dichroism. In addition, we obtain images of the transient absorption and transient phase for the two orthogonal probe polarization components, thereby achieving a complete characterization of the ultrafast chiroptical response over a wide field of view (50 × 50 µm2) with high temporal (~100-fs) and spatial (submicrometre) resolution. We demonstrate the capabilities of our technique by imaging spin relaxation in hybrid organic–inorganic perovskites. Finally, we study multisite spin diffusion using a matrix of diffraction-limited excitation spots. Our approach enables the spatiotemporal mapping of transient magnetic and electronic phenomena in a wide range of emerging functional materials, spanning biomolecules, chiral plasmonic nanostructures, and topological and spintronic materials.