Xu, J.J.XuGlobisch, B.B.GlobischHofer, C.C.HoferLilienfein, N.N.LilienfeinButler, T.T.ButlerKarpowicz, N.N.KarpowiczPupeza, I.I.Pupeza2022-03-052022-03-052018https://publica.fraunhofer.de/handle/publica/25700410.1088/1361-6455/aacfe7We demonstrate optical rectification of 1 mm pulses with a duration of 20 fs, a repetition-rate of 78 MHz and an average power of 5.5 W, in a 2 mm thick GaP crystal. The spectrum of the resulting far-infrared pulses is centered at 1.5 THz and extends to 5 THz at −50 dB intensity. In the absence of resonant absorption of GaP in this range, the spectrum has a well-behaved shape, facilitating spectroscopic applications. In the context of the recent rapid evolution of high-power Yb-based femtosecond laser systems, these results show a viable route towards sources of THz pulses combining broad bandwidth, high average power and a smooth spectral shape.en621530journal article