Reshaping of Freely Propagating Terahertz Pulses by Diffraction

We discuss the application of diffraction theory to the reshaping of freely propagating terahertz pulses by narrow apertures. This is accomplished by using two separate electrooptic sampling detectors. The first contains a narrow electrode geometry that does not modify the frequency content of the incident terahertz field, while the second contains a narrow gap between two large electrodes. The latter detector transforms the incident bipolar terahertz waveform into a unipolar waveform. We find that diffraction theory properly accounts for this reshaping process. We discuss the applicability of alternate electrode geometries for terahertz pulse shaping.