Ultrafast Nano-Spectroscopy | Page 5

neaSCOPE + fs simultaneously measures multiple near-field harmonics that scoop different sample volumes , thus enabling depth-sensitive investigation of carrier dynamics . Largest optical access to the probing tip allow for unprecedented beampath customization including for non-local pump-probe nano-imaging .

THz s-SNOM , au

Depth dependence of carrier dynamics

neaSCOPE + fs allows for depth dependent investigation of transient carrier dynamics based on the measurement of s-SNOM signal demodulated at higher harmonics of the tip tapping frequencies s n that scoop smaller sample volumes . Varying time decay of the THz signal in of GaAs nanobars measured by ultrafast THz nanoscopy could indicate different relaxation time at the surface vs . bulk , suggesting an electron band bending and emphasizing a crucial role of interfaces onto the electron response in nanostructures .

Non-local ultrafast THz nanoscopy neaSCOPE + fs customized to independently focus near-IR pump & THz probe beams enabled femtosecond-resolved investigation of nonlocal diffusion of photoexcited charge carriers in undoped GaAs nanowires . The appearance of THz contrast in the nanowire indicates the arrival of charges from the pump region . neaSCOPE + fs accurately timed the phenomenon , providing carrier diffusion time and elucidating strong anisotropy with respect to the nanowire axis , which demonstrates a capability to measure carrier drift / diffusion velocities in materials with anisotropic optoelectronic properties .