Single-Cycle Terahertz Pulse Generation via Superimposed Diffraction With Cherenkov Effect

The ultrashort terahertz (THz) pulse with a broad frequency spectrum has important applications in THz spectroscopy and imaging. Previous THz-pulse generating methods are restricted by either low power or high cost. Here, we propose a novel scheme for generating ultrashort THz pulses, which uses a low-energy sheet electron beam to drive an inclined array of size-graded grooves. The diffraction radiation (DR) from each groove is successively generated and coherently superimposed at a specified direction via the Cherenkov effect. A single-cycle THz pulse with a spectrum band covering the region from 0.1 to 1 THz can be realized. In addition, using several arrays of grooves, a train of ultrashort THz pulses can be further obtained. The radiation power, which depends on the beam current, reaches as high as several kilowatts by using available electron beams. It affords an effective way of generating ultrashort THz pulses with broad application prospects.