REFLECTION- AND/OR DIFFRACTION-BASED METHOD AND SETUP TO GENERATE HIGH-ENERGY TERAHERTZ PULSES

摘要

The present invention is directed to a novel technique to generate terahertz radiation. According to the inventive technique, a pump beam (12) is coupled into an optical element (50) made of a medium with non-linear optical properties having plane-parallel front and rear boundary surfaces (51, 52), wherein the pump beam (12) is split into a set of partial pump beams (121 ) by reflection and/or diffraction on a periodic relief structure (53) formed in the rear boundary surface (52) of said optical element (50). The partial pump beams travel along a direction which is characterized by an angle γ that satisfies the velocity matching condition of v p,cs cos(γ) = v THz ,ƒ within the given medium, where v p;cs is the group velocity of the pump beam, v THz;f is the phase velocity of the terahertz radiation, and γ is the angle formed by the pulse front envelope and the phase front of the pump beam. The envelope (212) of the pump pulse front segments (221 ) propagating in the partial pump beams travels at a velocity v THz;f of the terahertz radiation (60) towards the front boundary surface (51 ) of the optical element (50) and generates terahertz radiation in the nonlinear optical medium through nonlinear optical interaction.