Next-generation communication / security / surveillance / sensing systems for civilian, defense, space or airborne applications, require real-time ultra-fast self-reconfigurable devices to efficiently optimize their performances (data rate, quality of service, resolution, or even discretion). In this context, the MUFRED project aims at demonstrating the ideal capabilities of the Metal Insulator phase Transition (MIT) materials such as vanadium dioxide (VO2) for the fabrication of new electronic ultra-fast reconfigurable microwave components taking benefit of the optical activation (or electrical activation as a back-up solution) of the transition. To this end, we will develop well-controlled thin films and evaluate the performances of such optically-controlled electronic devices through attainable and measurable objectives.
The main objectives of MUFRED are:
1/ to better understand the physical properties of semiconducting, intermediate and metallic states (electronic conductivity and mobility), and the role of structures/microstructures on the transition (dynamic, width, temperature).
2/ to integrate this material with new or existing planar lines technologies for manufacturing optically-controlled (or electrically-controlled) switches and associated devices.
3/ to get full control of the electronic transition by photonic absorption and/or electronic injection of charge carriers in order to reach shorter switching time (0.1-100 ns), understand the main relaxation mechanisms using THz pump probe spectroscopy,
4/ to exploit the unique properties of VO2 for demonstrating relevant pioneer proofs-of-concepts, namely ultra-fast optically-reconfigurable microwave devices (switches, filters, phased antennas), and exploring advanced concept of such devices (reconfigurable reflectarrays).
Particularly, three reference devices have been selected to demonstrate the potential applications of VO2 and so far MIT materials. The first one is ultra-fast RF switch in a coplanar structure with low insertion loss (<0.2dB), high isolation (<-30dB) and ultra-fast switching time (ST) lower than 100 ns. Optical commands will be investigated, based on both a 6-THz phonon/electron interaction and/or a high optical absorption due to specific doped materials.
Such RF switches will be used as building blocks and integrated in fully reconfigurable circuits and phase array antennas. Finally the knowledge in terms of materials, properties and devices and their correlations will be exploited to develop a more complex optically-controlled reflectarray antenna with ultra-fast beam reconfiguration, thus leading to a first demonstration at the international level.
Seven partners (5 academic, 2 industrial) are involved in MUFRED project, which is organized in 7 work-packages (WP) from material deposition and MIT understanding / development to the fabrication of ultra-fast reconfigurable devices. WP1 deals with management and result exploitation. 2D growth of VO2 thin films will be controlled by both PLD and MOCVD on single crystals of TiO2 and Al2O3 substrates; elaboration of sub-layers and/or of doping will be investigated in particular on Si substrate (WP2). In both states and during the transition, suitable material characterizations will be carried out to understand the mechanisms involved in particular the crucial role played by electronic rearrangement and vibrational modes of the atomic structure (WP3). Time–resolved spectroscopies studies will be performed to provide a specific understanding of the optically induced MIT mechanisms (WP4). After developments and validations of the specific thin film technological steps, a RF-switch based-VO2 first demonstrator will be presented as an ideal building block for ultra-fast optically- (or electrically-) reconfigurable RF switches (WP5). More advanced optically-controlled proof-of-concepts will be demonstrated like filters, phase shifters and phased arrays antenna (WP6); the final demonstrator will be the first optically-reconfigurable reflectarray antenna (WP7) ever proposed.