Abstract-Enhancing THz generation in photomixers using a metamaterial approach

Daniel J. Ironside, Rodolfo Salas, Pai-Yen Chen, Khai Q. Le, Andrea Alú, and Seth R. Bank

Fig. 1 As illustration depicting key photomixer design features between (a) the conventional photomixer design and (b) the proposed enhanced metamaterial design.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-7-9481

Photomixers at THz frequencies offer an attractive solution to fill the THz gap; however, conventional photomixer designs result in low output powers, on the order of microwatts, before thermal failure. We propose an alternative photomixer design capable of orders of magnitude enhancement of continuous-wave THz generation using a metamaterial approach. By forming a metal-semiconductor-metal (MSM) cavity through layering an ultrafast semiconductor material between subwavelength metal-dielectric gratings, tailored resonance can achieve ultrathin absorbing regions and efficient heat sinking. When mounted to a tunable E-patch antenna, gratings also act as vertically biased electrodes, further enhancing photoconductive gain by reducing the carrier path length to nanoscales. Thus, through these multiplicative enhancements, the metamaterial-enhanced photomixer is projected to generate THz powers in the milliwatt range and exceed the Manley-Rowe limit for frequencies less than 2 THz.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Boosting Terahertz Photoconductive Antenna Performance with Optimised Plasmonic Nanostructures

Sergey Lepeshov, Andrei Gorodetsky, Alexander Krasnok, Nikita Toropov, Tigran A. Vartanyan, Pavel Belov, Andrea Alú, Edik U. Rafailov,

https://www.nature.com/articles/s41598-018-25013-7


Advanced nanophotonics penetrates into other areas of science and technology, ranging from applied physics to biology, which results 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 their arrangement, we obtain an enhancement of optical-to-THz conversion efficiency 2-fold larger compared with previously reported results for similar structures, and the strongest enhancement is around 1 THz, a frequency range barely achievable by other compact THz sources. We also 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.