Multi-Pixel Interdigitated Photoconductive Devices for Terahertz Polarization Control and Imaging

In this work we propose and experimentally verify multi-pixel interdigitated photoconductive devices for broadband THz polarization control [1] and imaging. To create arbitrary linear polarisation states, an array of horizontally and vertically polarized THz radiation dipoles was produced using a patterned photoconductive antenna, as illustrated in Fig. 1(a) and 1(b). Here a 2 × 2 grid of pixels, with the electrodes in each pixel arranged orthogonally to those in the adjacent pixels. In a photoconductive emitter, the direction of the bias field between the electrodes defines the direction of acceleration of the photoexcited charge carriers, and therefore the polarization state of the generated THz radiation, demonstrated by the arrows in Fig. 1(b). Photoexciting the device and varying the relative strengths of horizontal and vertical bias (V
_H
and V
_V
) varied the relative strengths of the horizontally and vertically polarized components of the generated THz radiation. In the far-field, where the contributions from each pixel overlap, the polarization state of the THz pulse was the superposition of the horizontal and vertical components.