▎ 摘　　要

We experimentally observed the fast relaxation and relatively slow recombination dynamics of photogenerated electrons/holes in a heteroepitaxial graphene-on-Si material under pumping with a 1550-nm, 80-fs pulsed fiber laser and probing with the corresponding terahertz beam generated by and synchronized with the pumping laser. The time-resolved electric-nearfield intensity originating from the coherent terahertz photon emission is electrooptically sampled in total-reflection geometry. The Fourier spectrum fairly agrees the product of the negative dynamic conductivity and the expected THz photon spectrum reflecting the pumping photon spectrum. This phenomenon is interpreted as an amplified stimulated terahertz emission.