Broadband THz detection with graphene flakes

We demonstrate a broadband THz detector based on graphene flakes, which are produced by scotch-tape method on SiO2/Si, combined with a logarithmic periodic antenna. The antenna is coupled to the graphene flake with an interdigitated comb-like structure in the center. The detectors were characterized at roomtemperature using the free-electron laser FELBE at the Helmholtz-Zentrum Dresden-Rossendorf. The responsivity is above 1nA/W for wavelengths from 30µm to 220µm. The rise time of the measured signals is below 100ps and their length is in the range of 200ps, while the pulse duration of the FEL pulses is around 20ps. The effect of the antenna coupling could be confirmed via polarization dependent measurements. Due to the spectral bandwidth combined with high temporal resolution and simple handling these detectors can be very useful for timing purposes of short laser pulses.