SEA TADPOLE · Studying ultrafast opto-magnetism in space and time with femtosecond temporal resolution and nanometer spatial resolution

Ultrafast magnetization is of great interest, because new developments in this field could lead to faster, more compact magnetic recording technology where the ultimate technological goal is “smaller and faster” . Central to addressing this challenge is the development of novel experimental tools to directly look at the interplay between magnetism and individual nanostructures resulting from the quantum mechanical exchange interaction . Here we propose working towards an instrument that has unique capabilities for measuring the temporal spin dynamics of magnetic nanostructures with subwavelength spatial resolution as a first step towards understanding and controlling spindynamics on both nanometer spatial and femtosecond temporal scales. To achieve measurements on these unprecedented scales, we will combine two powerful techniques: Near Field Scanning Optical Microscopy (NSOM), which allows for nanometer-scale spatial resolution and a variant of Spectral Interferometery which allows for complete measurement of the light’s electric field (i.e. the intensity and the phase) on a femtosecond time scale. This will be implemented in a pump-probe configuration using NSOM in excitation mode to probe the sample with a subwavelength spot of light having a well defined spectral phase and polarization state. By scanning the probe pulse across the sample we can measure E(t,x,y) of the probe with femtosecond temporal and nanometer spatial resolutions which should reveal how the ultrashort pulse evolves in space and time as it interacts with the magnetic nanostructure. This will in turn reveal the temporal evolution of the material properties at each spatial location on the sample. By pushing the temporal and spatial resolutions of time-resolved magnetic imaging to its limit , we hope to provide deeper insight into the underlying physics. This could have important implications for both our scientific understanding of magnetism and and for the future of magnetic storage technology.