  Advanced nanophotonics penetrates into other areas of science and technology,
ranging from applied physics to biology and resulting in many fascinating
cross-disciplinary applications. It has been recently demonstrated that
suitably engineered light-matter interactions at the nanoscale can overcome the
limitations of today's terahertz (THz) photoconductive antennas, making them
one step closer to many practical implications. Here we push forward this
concept by comprehensive numerical optimization and experimental investigation
of a log-periodic THz photoconductive antenna coupled to a silver nanoantenna
array. We shed light on the operation principles of the resulting hybrid THz
antenna, providing an approach to boost its performance. By tailoring the size
of silver nanoantennas and the distance between them, we obtain an enhancement
of optical-to-THz conversion efficiency 2-fold larger compared with previously
reported results, and the strongest enhancement is around 1 THz, a frequency
range barely achievable by other compact THz sources. Moreover, we propose a
cost-effective fabrication procedure to realize such hybrid THz antennas with
optimized plasmonic nanostructures via thermal dewetting process, which does
not require any post processing and makes the proposed solution very attractive
for applications.
