Highly efficient carrier multiplication and bright exciton luminescence under intense terahertz pulse

The nonlinear interactions of GaAs quantum wells with intense single cycle terahertz (THz) pulses with amplitudes exceeding 1 MV/cm have been studied. We demonstrated for the first time that the number of carriers is enhanced 10³ times more with an increase of the electric field amplitude of the THz pulse from 0.5 to 1 MV/cm, eventually which leading a bright near infrared luminescence. This highly efficient carrier multiplication process with a threshold-like behavior implies that the carriers driven under intense THz pulse can efficiently gain enough high kinetic energy to induce cascading impact ionizations.