Towards femtosecond electronics based on single-walled carbon nanotubes

To combine the advantages of ultrafast femtosecond optics with an on-chip communication scheme, optical signals with a frequency of several hundreds of THz need to be down-converted to coherent electronic signals of GHz or less. Here, we present an optoelectronic measurement scheme that allows for the direct read-out of ultrafast electronic nonequilibrium processes in nanoscale circuits. Particular, we demonstrate that photocurrents in single-walled carbon nanotubes (CNTs) under a resonant optical excitation of their subbands can be ballistic on subpicosecond timescales. The investigated semiconducting CNTs are integrated as functional parts of on-chip THz stripline circuits. In turn, the ballistic currents in the CNTs drive THz transients in the on-chip THz circuits with a bandwidth of up to 2 THz. The transients propagate within the striplines on a macroscopic, millimeter scale. Our results pave the way towards femtosecond on-chip electronics based on single-walled CNTs.