Scaling up the energy of THz pulses created by optical rectification

The possibility for up-scaling the energy of sub-ps THz pulses generated by tilted pulse front excitation is demonstrated. Using 150-fs-long 500 mu J optical pump pulses at 800 nm up to 240 nJ THz pulse energy has been achieved. For a 1.2 mm(2) pump spot area, the energy conversion efficiency of pump energy to THz pulse energy had a maximum of 5 x 10(-4) at 300 mu J pump pulse energy. The corresponding photon conversion efficiency amounts to 10%. For comparison, the maximum attainable THz pulse energy was limited to 3.1 nJ if a line focusing excitation geometry was utilized. This limit was reached at 32 mu J pump energy. For the latter configuration the THz energy dropped for larger pump energies. The tilted pulse front excitation allows further up-scaling of the THz pulse energy by using a larger pump spot size and still stronger pump pulses. (C) 2005 Optical Society of America.