We report on the observation of a radiation helicity sensitive photocurrent
excited by terahertz (THz) radiation in dual-grating-gate (DGG)
InAlAs/InGaAs/InAlAs/InP high electron mobility transistors (HEMT). For a
circular polarization the current measured between source and drain contacts
changes its sign with the inversion of the radiation helicity. For elliptically
polarized radiation the total current is described by superposition of the
Stokes parameters with different weights. Moreover, by variation of gate
voltages applied to individual gratings the photocurrent can be defined either
by the Stokes parameter defining the radiation helicity or those for linear
polarization. We show that artificial non-centrosymmetric microperiodic
structures with a two-dimensional electron system excited by THz radiation
exhibit a dc photocurrent caused by the combined action of a spatially periodic
in-plane potential and spatially modulated light. The results provide a proof
of principle for the application of DGG HEMT for all-electric detection of the
radiation's polarization state.Comment: 7 pages, 4 figure
