Circular-Photon-Drag-Effect-Induced Elliptically Polarized Terahertz Emission from Vertically Grown Graphene

The circular photon drag effect (CPDE) is important for helicity-dependent optoelectronic emitters and detectors, but in graphene the relatively weak light-matter interaction gets drowned out by other nonlinear optical effects. Vertically grown graphene (VGG), though, with its particular symmetry point group, can exclude the other effects and enhance the light-graphene interaction. This study of the CPDE from VGG shows that the emitted THz states can be tuned to have linear or left- or right-handed elliptical polarization, by changing the helicity of the pump laser. This observation points to graphene-based polarization-sensitive THz sources for chiral analysis.