Near field of terahertz radiation transmitted through a lateral non-centrosymmetric grating

The transmission of a terahertz (THz) wave through a grating of metallic strips deposited on a flat surface of a dielectric medium has been considered. It has been assumed that the unit cell of the lateral grating does not have a spatial inversion center and the grating period is small compared to the radiation wavelength. The found amplitudes and phases of the spatial harmonics of the transmitted wave in the near field have been used to calculate the components of the tensor of asymmetry parameters responsible for the generation of photocurrents in a doped quantum well embedded in the non-centrosymmetric system under consideration. It has been found that, at a strip height greater than the skin depth, the parameters of the transmitted spatial harmonics are nearly independent of the height. It has been shown that the metallic grating exhibits strong birefringence, and the radiation polarized either circularly or linearly at an angle of 45° with respect to the principal axes of the lateral grating induces superposition of photocurrents owing to the circular or linear electronic ratchet effects.