Coherent synthesis of THz wave profiles

Coherent synthesis of THz wave spatial profiles was observed using real-time THz imaging. We used an array of photoconductive antennas pumped by femtosecond optical pulses as a THz wave source. Emitted THz pulses were focused and the spatial profile on the focal plane, which is a coherent superposition of output from each unit, was observed by realtime THz imaging using the EO sampling method. By inverting the bias voltage applied to the central unit of the antenna array, a super-resolution effect was observed, where the THz spot sizes was smaller than when a voltage was applied to all the unit in the same direction.