Ultrafast terahertz Faraday rotation in graphene

Abstract

Terahertz (THz) Faraday rotation measurements were performed to investigate carrier dynamics in p-type Chemical vapor deposition (CVD) graphene. We used static and time-resolved polarization-sensitive THz transmission measurements in a magnetic field to probe free carriers in GaAs, InP, and Graphene. Static measurements probe the equilibrium carrier density and momentum scattering rate. Time-resolved (optical pump/THz probe) measurements probe the change in these quantities following photoexcitation. In a typical CVD graphene sample, we found that 0.5 ps following photoexcitation with 1 × 1013 photons/cm2 pulses at 800 nm the effective hole scattering time decreased from 37 fs to 34.5 fs, while the carrier concentration increased from 2.0 × 1012 cm-2 to 2.04 × 1012 cm-2, leading to a transient decrease in the conductivity of the film.