Our research builds on our earlier demonstration of THz radar using a leaky-wave device to both transmit a broadband signal, and to receive back-reflected signals from objects in the environment. That result inspired a demonstration of a low-profile THz bar code reader. Using a parabolic optic, we convert the output of the leaky-wave antenna (a fan-like rainbow beam) into a quasi-parallel beam with a strong frequency chirp across its wave front. This beam can then be directed at an artificial bar code consisting of a set of flat parallel metal reflecting bars. The presence (or absence) of a bar gives rise to the presence (or absence) of a particular frequency component in the received back-reflection. In our demonstration, the bar code can contain up to 64 bits of information, and can be implemented by printing a metallic pattern on the back of a piece of paper. As a result, it is not only essentially free to create the bar codes, but these patterns can be hidden from visible view. A scanning system of this sort could be valuable in situations in which covert communication is required. The work has been published in Optics Express.
Publications
Yasith Amarasinghe, Hichem Guerboukha, Yaseman Shiri, and Daniel M. Mittleman, “Bar code reader for the THz region,” Optics Express, 29, 20240-20249 (2021)