  Recent intense electrical and optical studies of graphene have pushed the
material to the forefront of optoelectronic research. Of particular interest is
the few terahertz (THz) frequency regime where efficient light sources and
highly sensitive detectors are very challenging to make. Here we present THz
sources and detectors made with graphene field effect transistors (GFETs)
enhanced by a double-patch antenna and an on-chip silicon lens. We report the
first experimental observation of 1-3 THz radiation from graphene, as well as
four orders of magnitude performance improvements in a GFET thermoelectric
detector operating at ~2 THz. The quantitative analysis of the emitting power
and its unusual charge density dependence indicate significant non-thermal
contribution from the GFET. The polarization resolved detection measurements
with different illumination geometries allow for detailed and quantitative
analysis of various factors that contribute to the overall detector
performance. Our experimental results represent a significant advance towards
practically useful graphene THz devices.
