Phase-change chalcogenide photonics
Carlos Ríos*,1, Matthias Stegmaier2, Peiman Hosseini1, David Wright3, Wolfram Pernice2 & Harish Bhaskaran1
1 Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK
2 Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
3 Department of Engineering, University of Exeter, Exeter, EX4 QF, UK
Phase-change materials (PCMs) are chalcogenide compounds capable of switching
back and forth between two optically and electrically differentiable crystallographic
structures namely the crystalline and the amorphous states. Alloys such the nucleation
and the growth dominated Ag3
(AIST) present long state retention and can be precisely switched by means of optical or electrical pulses. Despite these unique properties being of great potential, PCMs based technologies have been mostly limited to non-volatile digital memories, leaving aside other developments in the optical domain that could be enabled by materials with such large refractive index contrast. Recently, however, we have explored new approaches merging phase-change materials and photonic devices to overcome well known limitations such as the lack of active materials for static tunability in on-chip integrated photonic circuits. To do so, we have placed nanoscale junctions of PCMs onto nanophotonic waveguides and have demonstrated optical switching that could lead to the realisation of integrated memories and light modulators . Furthermore, the possibility of switching with both optical and electrical pulses gives rise to hybrid electro-optical applications at different scales. In this direction, we have proposed a new optoelectronic framework, using both growth and nucleation dominated materials within nanocavities, to modulate colours of thin flexible films in pixels as small as 100 nm . The combination of Photonics and PCMs is therefore a highly promising field that could lead to future novel implementations, for instance in on-chip unconventional computing architectures , ultrathin flexible bistable displays, and electro-optical sensors, filters and modulators.
 P. Hosseini, C.D. Wright and H. Bhaskaran, Nature 511, 206 (2014)
 C. Rios , P. Hosseini , C.D. Wright , H Bhaskaran and W H P Pernice, Adv. Mater. 26, 1372 (2014)
 C.D. Wright, Y. Liu, K.I. Kohary, M.M. Aziz, R.J. Hicken, Adv. Mater. 23, 3408 (2011)