Terahertz Radiation from a Thin GaAs Crystal in a Metallic Tapered Parallel Plate Waveguide

Terahertz generation in a thin (100-µm thick) GaAs crystal sandwiched between the walls of a metallic tapered parallel plate waveguide at its narrow end and pumped by a 1560-nm femtosecond laser has been experimentally studied. The terahertz radiation characteristics are compared with those from a thick bulk GaAs crystal in a free space. The results demonstrate that the taper structure improves the directivity of terahertz emission from thin crystals pumped by focused optical beams.