Enhanced terahertz emission in a large-area photoconductive antenna through an array of tightly packed sapphire fibers

Experimental observation of the enhanced terahertz (THz) emission in a large-area photoconductive antenna-emitter (LAE), boosted by an array of cylindrical sapphire-fiber-based microlenses, is reported. The observed enhancement is achieved, thanks to the sharp focusing of a pump laser beam near the semiconductor surface, for which the high-refractive-index sapphire lenses are used. We predict numerically and confirm experimentally a considerable enhancement in the emitted THz spectral power for such a sapphire-fiber-coupled LAE, as compared to an ordinary one with an equal electrode topology. In fact, a ≃ 8.5-fold THz power boost is achieved, resulting in a +9.3 dB increase in the dynamic range. The results of our findings can be used to improve the performance of large-area THz devices, aimed at meeting the demands of rapidly developed THz spectroscopy, imaging, sensing, and exposure technologies.