Free-standing tapered probe-tip for high resolution photoconductive terahertz field sampling

We present a photoconductive probe-tip applicable for near- and far-field measurements in the terahertz frequency range. The probe-tip is based on a triangular patch of freestanding LT-GaAs of only 1.3 mum thickness with a pair of tapered metallic wires on top. Using non-resonant electric field enhancement at the tip of the probing device a spatial resolution of 5 mum and a bandwidth of 2 THz is demonstrated.