Abstract
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.
Highlights
Optical signaling has dominated long-distance communications for decades
While promising approaches to the realization of integrated photonic memories have been developed over the years, these led to devices that were essentially inherently volatile, often requiring a steady energyconsuming optical bias to preserve the stored state
In conclusion, we have shown that by using plasmonic enhancement we can greatly increase the strength of the light-matter interaction occurring in integrated phase-change photonic memory cells
Summary
Optical signaling has dominated long-distance communications for decades. More recently, chip-to-chip and even on-chip optical signaling have gained traction, in particular due to the rising influence of silicon photonics [1,2,3]. By incorporating PCM cells into chip-scale photonic devices, all-optical arithmetic processing, neuromorphic and in-memory computing are possible [12,13,14] In such memory and processing applications using integrated phase-change photonic devices, the basic mode of operation involves switching, using light guided down an integrated waveguide, the PCM cell between its crystalline and amorphous states (or to intermediate states between the two). Such switching results in a non-volatile and reversible modification of the waveguide’s optical transmission, forming the basis of the readout process - see Fig. 1(a). This, coupled with a substantial reduction in the volume of phase-change material that undergoes switching (as compared to the conventional approach of Fig. 1(a)), leads to quite dramatic improvements in both switching speed and energy consumption
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