  We demonstrate high-energy terahertz generation from a large-aperture (75 mm
diameter) lithium niobate wafer by using a femtosecond laser with energy up to
2 J. This scheme utilizes optical rectification in a bulk lithium niobate
crystal, where most terahertz energy is emitted from a thin layer of the rear
surface. Despite its simple setup, this scheme can yield 0.19 mJ of terahertz
energy with laser-to-terahertz conversion efficiencies of ~0.01%, about 3 times
better than ZnTe when pumped at 800 nm. The experimental setup is up-scalable
for multi-mJ terahertz generation with petawatt laser pumping.
