  A tilted-pulse-front pumped terahertz pulse source is proposed for the
generation of extremely high field single-cycle terahertz pulses. The very
simple and compact source consists of a single crystal slab having a blazed
reflection grating grooved in its back surface. Its further important
advantages are the energy scalability and the symmetric THz beam profile.
Generation of 50 MV/cm focused field with 5.6 mJ terahertz pulse energy is
predicted for a 5 cm diameter LiNbO$_3$ crystal, if the pump pulse is of 450 mJ
energy, 1030 nm central wavelength and 1 ps pulse duration. Such sources can
basically promote the realization of THz driven electron and proton
accelerators and open the way for a new generation concept of terahertz pulses
having extreme high field.
