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Plasmonic-Silicon-Organic Hybrid – a Universal Platform for THz Communications

Periodic Reporting for period 1 - PLASILOR (Plasmonic-Silicon-Organic Hybrid – a Universal Platform for THz Communications)

Reporting period: 2015-11-01 to 2017-04-30

Forecasts predict unprecedented growth for the mobile communications sector. Sub-THz systems are considered a solution to overcome the wireless speed bottleneck. A strong potential comes from the THz frequency window, offering unprecedented amount of communication bandwidth and speed, while featuring low atmospheric losses thus allowing large distance communications. In addition, THz wave technologies are also increasingly important for imaging, medical and spectroscopy applications.
Despite such a tremendous growth projected for THz technologies, there is no real large scale integration solution for THz components that would make the technology affordable. The PLASILOR project aims at combining the best of three worlds by bringing silicon, organic and plasmonic technologies onto one common platform to enable a THz revolution. Within PLASILOR, we develop novel devices that outperform the current state-of-the-art in terms of functionality, speed and size thanks to unique characteristics only offered by silicon, organics and plasmonics.
The overall objective of PLASILOR is to innovate a novel plasmonic-silicon-organic hybrid platform that combines the advantages of silicon, organics and plasmonics to offer low cost, large scale integration with novel features such as emission and a linear electro-optic effect. In detail, it focuses on the design and fabrication of novel highly integrated ultra-compact MZ and IQ modulators with frequency responses reaching sub-THz speeds; create novel detectors, sources and THz components; use them to demonstrate novel THz radio-over-fiber links. Novel numerical methods are also developed to accurately simulate and optimize these novel structures.
The project PLASILOR has the scope of combining silicon, organic nonlinear materials and plasmonic technologies onto a single platform. Over the first reporting period, we have demonstrated progress towards this target in each of the envisioned objectives, according to the schedule. Details are reported in the Progress Report document. In summary, major achievements have been obtained in the following research actions:
• Novel technology components: we have demonstrated all-plasmonic optical fiber to chip couplers capable of directly coupling light from multi-core optical fibers to plasmonic phase modulators.
• Plasmonic modulators: We have demonstrated a plasmonic Mach-Zehnder modulator with a flat frequency response exceeding 170 GHz, and plasmonic IQ-modulators with a record small footprint that operate up to 72 GBd. We have also experimentally shown that the overall losses, the power consumption and the footprint of plasmonic electro-optic modulators can be reduced when a device is operated in the vicinity of absorption resonances of an electro-optical material.
• Novel plasmonic photodetector: a novel concept of a photoconductive plasmonic photodetector based on the electro-absorption effect in a plasmonic slot-waveguide with amorphous Ge as active material has been experimentally demonstrated.
• Novel THz components: we have integrated a plasmonic phase modulator directly with an antenna operating at 60 GHz and demonstrated direct conversion from mm-wave signal to optical phase modulated signals, without the need of any electronics.
• Novel THz links: we reported an ultra-fast (GHz speed) antenna beam steering demonstration using plasmonic phase modulators to control the electrical phase of signals radiated by an array of antennas operating at 60 GHz.
• Simulation methods and optimized plasmonic modulators design: Optimization of fibre-to-modulator coupling and of plasmonic Mach-Zehnder modulator have been performed. A scheme for direct coupling from a multicore-fibre to a plasmonic modulator was developed and optimized using a 3D Maxwell solver. The total conversion efficiency of this ultra-compact scheme is predicted to be -2.5 dB. A completely plasmonic MZM design was designed using a three dimensional finite element solver for electromagnetic fields. The simulated MZM characteristics show an extinction ratio about 25 dB, insertion loss of –8 dB and reflection losses of –11 dB.
No major problems nor delays or cancellations have been experienced.
PLASILOR provides a strong progress beyond the state of the art in many fields of research, ranging from modulator and detector technology, light sources, and telecommunications, as described in detail in the previous section. The expected impact for this progress spans all fields related to terahertz technology. In telecommunications, sub-THz systems are considered a solution to overcome the speed bottleneck for wireless connections. THz wave technologies are also increasingly important for imaging, medical and spectroscopy applications, the latter of particular importance for the detection of concealed weapons and explosives.