a revolutionary platform for advanced multi-signal systems

March 11, 2022

(News from Nanowerk) Current computer and telecommunications technologies use electrical charges (electrons) and light (photons) to transport information. However, a breakthrough in this field could be achieved by introducing mechanical vibrations – phonons – as a means of data transfer, in combination with the other two.

In order to lay the foundations for a new information technology, the researchers involved in the PHENOMEN project worked for nearly four years on the development of a phonon-based signal processing system that could be integrated into standard electronic chips.

The results of this study were recently published in an article by ACS Photonics (“Room-Temperature Silicon Platform for GHz-Frequency Nanoelectro-Opto-Mechanical Systems”) introducing a proof-of-concept technology platform for the integration of phononic, photonic and radio frequency (RF) electronic signals, which can be operated at ambient conditions and is fully compatible with CMOS technology. These remarkable results open up new avenues for information processing and transport, not only in current computing applications, but also in future quantum networks.

The researchers designed a coherent phonon source using the mechanism of opto-mechanical coupling, namely the interaction of radiation pressure forces with a resonator. The micro-scale resonator was designed to simultaneously maintain co-localized optical and mechanical modes.

The source of phonons results from an opto-mechanical interaction involving competing mechanisms: one from carriers photogenerated in the resonator and the other from the temperature variation of the resonator impacting its optical properties. This interaction leads to the generation of coherent vibrations, that is, acoustic waves in phase with each other.

Diagrams of the silicon platform for GHz NEOMS. (Picture: ICN2)

The basic material used to maximize the opto-mechanical interaction is nanocrystalline silicon (nc-Si), a technology developed at VTT – instead of standard crystalline silicon (c-Si) – which offers various advantages, such as: flexibility in optical tuning, mechanical and thermal properties of the system; and increased accessibility, since components can be fabricated on standard silicon wafers.

The conversion of electrical signals into mechanical waves is obtained by combining silicon with aluminum nitride (AlN), which is a piezoelectric material, that is, a material capable of producing electricity when application of mechanical stress. Both solutions represent a great innovation in the design and manufacture of NOEMS.

This new silicon-enabled platform for nano-electro-opto-mechanical systems, which converts electrical signals to optical signals via mechanical waves (and vice versa), has been shown to work at radio frequencies (up to ‘at a few GHz) and at room temperature, it can therefore be incorporated into CMOS manufacturing processes. Therefore, it has the potential to become a breakthrough solution for new multi-functional and multi-signal technologies for information transmission and processing, both in the classical and quantum domain.

The key components of this NEOMS platform were developed by a team of researchers from the Catalan Institute of Nanosciences and Nanotechnologies (ICN2, Barcelona, ​​Spain), CNR-Nano (Pisa, Italy), Polytechnic University of Valencia ( Spain) and VTT Technical Research Center (Espoo, Finland).

About the PHENOMEN project

PHENOMEN was a project funded by the European Union under the highly competitive H2020 FET-Open call 3 and coordinated by ICREA Prof. Dr. Clivia Sotomayor Torres, leader of the ICN2 Phononic and Photonic Nanostructures group. Launched in 2016, it brought together three leading research institutes – the Catalan Institute of Nanoscience and Nanotechnology (ICN2), the Italian National Research Council (CNR-NANO Pisa, Italy), the VTT Technical Research Center of Finland (VTT, Espoo, Finland)—, three internationally recognized universities – the Polytechnic University of Valencia (UPVLC, Spain), the Polytechnic University of Marche (UNIVPM, Italy), the University of Sciences and Technologies of Lille ( USTL, France)– and an industrial partner –MENAPiC SAS (Lille, France). Together, they combined complementary expertise in photonics, phononics, optomechanics, electrical engineering, integration, nanofabrication, theory and modelling, instrumentation and detector application.

The objective of the PHENOMEN project was to exploit the potential of combined phononic, photonic and radiofrequency (RF) electronic signals to lay the foundations for a new information technology. More specifically, it aimed to propose an implementation of integrated phononic circuits based on opto-mechanical cavities operating at ambient conditions. The developed platform will complement current state-of-the-art electronic and photonic circuits by extending the signal frequency range and will be based on fully CMOS compatible materials.

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