  The ability to resolve the polarization of light with on-chip devices
represents an urgent problem in optoelectronics. The detectors with
polarization resolution demonstrated so far mostly require multiple oriented
detectors or movable external polarizers. Here, we experimentally demonstrate
the feasibility to resolve the polarization of mid-infrared light with a single
chemical-vapor-deposited graphene-channel device with dissimilar metal
contacts. This possibility stems from an unusual dependence of photoresponse at
graphene-metal junctions on gate voltage and polarization angle. Namely, there
exist certain gate voltages providing the polarization-insensitive signal;
operation at these voltages can be used for power calibration of the detector.
At other gate voltages, the detector features very strong polarization
sensitivity, with the ratio of signals for two orthogonal polarizations
reaching ~10. Operation at these voltages can provide information about
polarization angles, after the power calibration. We show that such unusual
gate- and polarization-dependence of photosignal can appear upon competition of
isotropic and anisotropic photovoltage generation pathways and discuss the
possible physical candidates.
