  Phase-stable electromagnetic pulses in the THz frequency range offer several
unique capabilities in time-resolved spectroscopy. However, the diversity of
their application is limited by the covered spectral bandwidth. In particular,
the upper frequency limit of photoconductive emitters - the most widespread
technique in THz spectroscopy - reaches only up to 7 THz in regular
transmission mode due to the absorption by infrared-active optical phonons.
Here, we present ultra-broadband (extending up to 70 THz) THz emission from Au
implanted Ge emitter which is compatible with a fibre laser operating at 1.1
and 1.55 {\mu}m wavelengths at a repetition rates of 10 and 20 MHz,
respectively. This opens a perspective for the development of compact THz
photonic devices operating up to multi-THz frequencies and compatible with Si
CMOS technology.
