Up to 70 THz bandwidth from an implanted Ge photoconductive antenna excited by a femtosecond Er:fibre laser

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 the 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 an Au implanted Ge emitter which is compatible with modelocked fibre lasers operating at 1.1 and 1.55 um wavelengths with pulse repetition rates of 10 and 20 MHz, respectively. This result opens a perspective for the development of compact THz photonic devices operating up to multi-THz frequencies which are compatible with Si CMOS technology.