ACS Photon. http://doi.org/83z (2015)
An integrated device that can strongly modulate the intensity of terahertz (THz) waves could prove useful for various applications of terahertz photonics, including high-bit-rate free-space communications, imaging and sensing. Now, a graphene-based device with 100% modulation depth and a response speed of 110 MHz has been successfully integrated with a surface-emitting THz quantum cascade laser featuring a concentric circular grating. The large strength of the modulation is due to a strong interaction of the graphene with the laser field. The device was made by researchers from Nanyang Technological University, University of Leeds, Singapore Institute of Manufacturing and Hong Kong Polytechnic University. The broadband nature of graphene's absorption spectrum means that the approach reported here could, in principle, be scaled to other wavelength regions, such as the mid-infrared.