Chenyin Dai

Plasma-based terahertz (THz) sources are generally limited by a saturation effect and consequent optical-THz conversion efficiency. Extending plasma volume is an effective approach to mitigate the saturation effect and increase THz generation efficiency. By reshaping gas plasma using two pairs of cylindrical lens to focus two counter-propagating laser pulses, we demonstrate enhanced broadband coherent THz radiation through the interaction of colliding laser pulses with gas plasma.

Coherent polarization control of terahertz (THz) emission is crucial for applications in the THz field. Here, we demonstrate that the polarization of THz waves emitted from graphene through quantum interference can be coherently controlled by varying the relative phase between the co-circularly polarized laser fields. The polarization state of the THz wave emitted from graphene remains linearly polarized, while its direction can be arbitrarily changed by varying the relative phase.