Reconfigurable phase-change meta-absorbers with on-demand quality factor control

This is the final version. Available on open access from Optical Society of America via the DOI in this recordData accessibility: Supporting data for this manuscript is available from the corresponding author.Perfect absorber type devices are well-suited to many applications, such as solar cells, spatial light modulators, bio-sensors, and highly-sensitive photo-detectors. In such applications, a method for the design and fabrication of devices in a simple and efficient way, while at the same time maintaining design control over the key performance characteristics of resonant frequency, reflection coefficient at resonance and quality factor, would be particularly advantageous. In this work we develop such a method, based on eigenmode analysis and critical coupling theory, and apply it to the design of reconfigurable phase-change metasurface absorber devices. To validate the method, the design and fabrication of a family of absorbers was carried out with a range of ‘on-demand’ quality factors, all operating at the same resonant frequency and able to be fabricated simply and simultaneously on the same chip. Furthermore, by switching the phase-change layer between its amorphous and crystalline states, we show that our devices can provide an active or reconfigurable functionality.Office of Naval Research (ONR)Engineering and Physical Sciences Research Council (EPSRC)Office of Naval Research (ONR

Enhanced performance in plasmonic integrated phase-change memories

This is the final version.We here propose feasible strategies to improve the performance of integrated phase-change photonic memories by the use of plasmonic enhancement. Several solutions are investigated, focusing in particular on optimising the optical readout contrast (transmission modulation) that can be achieved between crystalline and amorphous states. Results show that by embedding the plasmonic nanoantenna within the body of the waveguide, or by using multiple coupled nanoantennas in series, significant improvements in optical readout contrast can be achieved, while maintaining relatively small insertion losses.European Union Horizon 202

A nonvolatile phase-change metamaterial color display

This is the final version. Available from Wiley via the DOI in this record.Chalcogenide phase-change materials, which exhibit a marked difference in their electrical and optical properties when in their amorphous and crystalline phases and can be switched between these phases quickly and repeatedly, are traditionally exploited to deliver nonvolatile data storage in the form of rewritable optical disks and electrical phase-change memories. However, exciting new potential applications are now emerging in areas such as integrated phase-change photonics, phase-change optical metamaterials/metasurfaces, and optoelectronic displays. Here, ideas from these last two fields are fused together to deliver a novel concept, namely a switchable phase-change metamaterial/metasurface resonant absorber having nonvolatile color generating capabilities. With the phase-change layer, here GeTe, in the crystalline phase, the resonant absorber can be tuned to selectively absorb the red, green, and blue spectral bands of the visible spectrum, so generating vivid cyan, magenta, and yellow pixels. When the phase-change layer is switched into the amorphous phase, the resonant absorption is suppressed and a flat, pseudowhite reflectance results. Thus, a route to the potential development is opened-up of nonvolatile, phase-change metamaterial color displays and color electronic signage.Engineering and Physical Sciences Research Council (EPSRC

Phase-change metadevices for the dynamic and reconfigurable control of light

This is the author accepted manuscript. The final version is available from Optical Society of America via the DOI in this recordNovel Optical Materials and Applications 2018, 2–5 July 2018, Zurich, SwitzerlandThe combination of chalcogenide phase-change materials with optical metamaterial arrays is exploited to create new forms of dynamic, tuneable and reconfigurable photonic devices including perfect absorbers, modulators, beam steerers and filters.CDW and VKN acknowledge ONRG funding (#N62909-16-1-2174). CDW, AMA, Y-YA, VKN acknowledge EPSRC funding EP/M015130/1 & EP/M015173/1. CrdeG, SG-CC, EG and LT the EPSRC CDT in Metamaterials (EP/L015331/1). LT acknowledges support from QinetiQ. MLG acknowledges EPSRC funding EP/M009033/1

Plasmonically-enhanced all-optical integrated phase-change memory

Integrated phase-change photonic memory devices offer a novel route to nonvolatile storage and computing that can be carried out entirely in the optical domain, obviating the necessity for time and energy consuming opto-electrical conversions. Such memory devices generally consist of integrated waveguide structures onto which are fabricated small phase-change memory cells. Switching these cells between their amorphous and crystalline states modifies significantly the optical transmission through the waveguide, so providing memory, and computing, functionality. To carry out such switching, optical pulses are sent down the waveguide, coupling to the phase-change cell, heating it up, and so switching it between states. While great strides have been made in the development of integrated phase-change photonic devices in recent years, there is always a pressing need for faster switching times, lower energy consumption and a smaller device footprint. In this work, therefore, we propose the use of plasmonic enhancement of the light-matter interaction between the propagating waveguide mode and the phase-change cell as a means to faster, smaller and more energy-efficient devices. In particular, we propose a form of plasmonic dimer nanoantenna of significantly sub-micron size that, in simulations, offers significant improvements in switching speeds and energies. Write/erase speeds in the range 2 to 20 ns and write/erase energies in the range 2 to 15 pJ were predicted, representing improvements of one to two orders of magnitude when compared to conventional device architectures