THz transient photoconductivity with near-field detection

We demonstrate a novel technique that enables the sub-diffraction near-field study of photo-excited structures probed with broadband THz radiation. As a proof-of-concept this system measures sub-ps temporal dynamics of photoexcited carriers in a thin film of GaAs with a spatial resolution of 60 gm (lambda\10 at 0.5 THz peak intensity).