  A new type of tilted-pulse-front pumped terahertz (THz) source has been
demonstrated, which is based on a lithium niobate plane-parallel slab with an
echelon structure on its input surface. Single-cycle pulses of 1 microjoule
energy and 0.30 THz central frequency have been generated with 0.05% efficiency
from such a source. One order-of-magnitude increase in efficiency is expected
by pumping a cryogenically cooled echelon of increased size and thickness with
a Ti:sapphire laser. The use of a plane-parallel nonlinear optical crystal slab
enables straightforward scaling to high THz pulse energies and to produce a
symmetric THz beam with uniform pulse shape for good focusability and high
field strength.
