Reflection and/or Diffraction-Based Method and Setup to Generate High-Energy Terahertz Pulses

A method to generate terahertz radiation (60) comprising:

• providing a plane-parallel optical element (50) formed of medium with nonlinear optical properties having a plane entry surface (51) and a rear boundary surface (52) parallel to the entry surface (51),
• coupling a pump beam (12) into the optical element (50) through the entry surface (51), perpendicularly to the entry surface (51),
• directing said pump beam (12) along a first propagation direction to one of:
• a periodic relief structure (53) formed in the rear boundary surface (52) of the optical element (50);
• or
• a periodic relief structure (153) formed in a surface (151) of an additional element (150), said surface (151) facing the rear boundary surface (52), extending parallel to the rear boundary surface (52) and being optically coupled to the rear boundary surface (52) of the optical element (50),
• subjecting the pump beam (12) to at least one of reflection or diffraction, splitting thereby the pump beam (12) into partial beams (121), said partial beams (121) having a common planar envelope (212), and
• generating terahertz radiation (60) by the partial beams (121), as pump beams, in the nonlinear optical medium through nonlinear optical interaction, and
• decoupling the terahertz radiation (60) from the optical element (50) through the entry surface (51),
• wherein said one of the periodic relief structure (53;
• 153) comprises:
• at least first zones perpendicular to the first propagation direction and parallel to each other,
• individual ones of said first zones having a symmetrical V-shape in a plane section along the first propagation direction, a magnitude of angles formed by legs of said V-shape and the rear boundary surface (52) being half an angle (γ) of pulse-front-tilting required to satisfy the velocity matching condition of
• vp,cs cos(γ)=vTHz,f (1)
• within the optical medium, wherein vp;cs is a group velocity of the pump beam (12), vTHz;f being is a phase velocity of the terahertz radiation (60) and γ is the angle of pulse-front-tilting, and
• wherein, after said reflection and/or diffraction, the partial beams (121) propagate at an angle γ to the first propagation direction, and the planar envelope (212) travels at a speed VTHz;f towards the entry surface (51) of the optical element (50).