EPSRC CDT in Metamaterials (PhD studentship): All dielectric phase-change metamaterial-based holography

University of Exeter - Departments of Physics and Engineering

Joint supervisors: David Wright, Jacopo Bertolotti, A Alexeev

Industrial supervisors: H Bhaskaran (Bodle Technologies Ltd)

All-dielectric metamaterials offer unique opportunities for the control of light on the nanoscale. Unlike the more conventional metal-based plasmonic metamaterials approaches, all-dielectric metamaterials exploit Mie resonances in dielectric nanoparticles (e.g. nanoscale silicon spheres or cylinders). This gives access to, and control of, large enhancements of both the electric and magnetic near-fields, in tandem with low dissipative losses. Dielectric metamaterials thus hold great promise for the development optical ‘metadevices’ that can control, with un-precedent efficiencies, the amplitude, phase or polarisation of light, with a range of important applications in such areas as optical displays, sensors, modulators, switches, filters etc. [1]. Dielectric metadevices developed to date are, however, essentially fixed-by-design, i.e. their properties are fixed and determined by the specific materials and geometries used. This places limits on their potential uses. If though we could introduce active, dynamic tuning of the dielectric properties of such metadevices, we would open up the route to a host of new and exciting applications including - the focus of this project – 3D holographic displays.

We will obtain active tuning control of all-dielectric metadevices by embedding in them thin layers of chalcogenide phase-change alloys (such as Ge2Sb2Te5 - or GST for short). These phase-change materials can be switched optically, electrically or thermally between their crystalline and amorphous states and in such states possess very different dielectric properties (permittivity). Exeter is a leading centre for phase-change materials and device research, and we have already developed a range of novel phase-change optoelectronic displays and integrated photonic devices [2 - 4]. The student appointed will thus benefit from joining a thriving and supportive research group environment that builds on and enhances the cohort and community aspects of the CDT itself.
In this project we will combine our metamaterials and phase-change expertise to develop novel all-dielectric metadevices. These will most likely consist of arrays of nanofabricated Silicon/GST nanostructures (typically cylinders), in which the electric and magnetic dipole (and higher-order) resonant frequencies can be separately controlled by tuning of the phase-state of the GST layer. In such a way we could have active and dynamic control of, for example, the reflected or transmitted optical phase of light incident onto the device. Preliminary work [5] has already shown that a full 2π of dynamic optical phase control should be possible, making the realisation of moving 3D holograms, the ultimate aim of this project, an enticing and practical possibility.

[1] A Kuznetsov et al. Science 354. Aag2472 (2016)
[2] P Hosseini, C D Wright and H Bhaskaran, Nature 511, 206 (2014)
[3] C Rios et al., Nature Photonics 9, 725 (2015)
[4] Z Cheng et al., Science Advances 3 (in press), (2017)
[5] A Alexeev et al., MRS Spring Mtg, Phoenix, USA (2017)

This studentship is part of the Centre of Doctoral Training in Metamaterials. Please see all fully funded opportunities.

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