Carlos Rios Ocampo1 2 Matthias Stegmaier3 Zengguang Cheng1 Nathan Youngblood1 C. David Wright4 Wolfram Pernice3 Harish Bhaskaran1

1, University of Oxford, Oxford, , United Kingdom
2, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
3, University of Münster, Münster, , Germany
4, University of Exeter, Exeter, , United Kingdom

On-chip all-optical switching of phase-change materials allows for non-volatile, sub-diffraction limit, and low insertion-loss reconfigurable photonic devices. This novel platform has already enabled non-volatile multilevel memories [1], an optical synapse [2], 1x2 optical switches [3], and on-chip computing [4] despite limited knowledge on the actual mechanism governing the phase switching. In this talk, we present a computational analysis of the switching behaviour of Ge2Sb2Te5 placed onto photonic waveguides and compare with experimental findings. In particular, we study the precise and reliable control of the amorphization and crystallization processes by means of evanescent field coupling between the confined mode and phase-change material. Furthermore, we study of the unique deterministic control of intermediate states, which enables the multilevel operation in this type of device. From a better understanding of the phase switching process, we then propose optimized parameters and geometries to improve the operation speed and energy consumption. The fundamentals of the switching mechanism offer a clearer perspective on the applicability and limitations of phase-change materials in on-chip reconfigurable optics and unconventional computing architectures.

[1] C. Ríos, M. Stegmaier, P. Hosseini, D. Wang, T. Scherer, C.D. Wright, H. Bhaskaran, W.H.P. Pernice. Integrated all-photonic non-volatile multi-level memory. Nat. Photonics. 9, 725–732. 2015.
[2] Z. Cheng, C. Ríos, W.H.P. Pernice, C.D. Wright, H. Bhaskaran, On-chip photonic synapse, Sci. Adv. 3 (9), e1700160. 2017.
[3] M. Stegmaier, C. Ríos, H. Bhaskaran, C.D. Wright, W.H.P. Pernice, Nonvolatile All-Optical 1X2 Switch for Chipscale Photonic Networks, Adv. Opt. Mater. 5 (1), 1600346, 2017.
[4] J. Feldmann, M. Stegmaier, N. Gruhler, C. Ríos, H Bhaskaran, C.D. Wright, W.H.P. Pernice. Calculating with light using a chip-scale all-optical abacus. Nat. Commun. In press, 2017.