Active THz beam shaping using a one-dimensional array of photoconductive emitters

Abstract

The spatial profile of a beam of pulsed terahertz (THz) radiation is controlled electrically using a multi-pixel photoconductive emitter, which consists of an array of interdigitated electrodes fabricated on semi-insulating GaAs. Activating individual pixels allows the transverse position of the THz beam's focus to be varied off-axis, as verified by spatial beam profiles. Enabling multiple pixels simultaneously permits non-Gaussian beam shapes to be created. The diffraction-limited performance of the system is established by comparison with the Abbé and Sparrow criteria, and a condition for effective beam steering using this design is derived. The spatial resolution of the approach is linked to the frequency of the THz radiation and the f-number of the collection optic.