Plasmonically-enhanced all-optical integrated phase-change memory.

Integrated phase-change photonic memory devices offer a novel route to non-volatile 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.