  We demonstrate a table-top high-field terahertz (THz) source based on optical
rectification of a collimated near-infrared pulse in gallium phosphide (GaP) to
produce peak fields exceeding 300 kV/cm with a spectrum centered at 2.6 THz.
The experimental configuration, based on tilted-pulse-front phase matching, is
implemented with a phase grating etched directly onto the front surface of the
GaP crystal. Although the THz generation efficiency starts showing a saturation
onset as the near-infrared pulse energy reaches 0.57 mJ, we can expect our
configuration to yield THz peak fields up to 866 kV/cm when a 5 mJ generation
NIR pulse is used. This work paves the way towards broadband, high-field THz
sources able to access a new class of THz coherent control and nonlinear
phenomena driven at frequencies above 2 THz.
