Integrated non-volatile plasmonic switches based on phase-change-materials and their application to plasmonic logic circuits

Rajib Ratan Ghosh,Anuj Dhawan

doi:10.1038/s41598-021-98418-6

Abstract

Integrated photonic devices or circuits that can execute both optical computation and optical data storage are considered as the building blocks for photonic computations beyond the von Neumann architecture. Here, we present non-volatile hybrid electro-optic plasmonic switches as well as novel architectures of non-volatile combinational and sequential logic circuits. The electro-optic switches consist of a plasmonic waveguide having a thin layer of a phase-change-material (PCM). The optical losses in the waveguide are controlled by changing the phase of the PCM from amorphous to crystalline and vice versa. The phase transition process in the PCM can be realized by electrical threshold switching or thermal conduction heating via external electrical heaters or the plasmonic waveguide metal itself as an integrated heater. We have demonstrated that all logic gates, a half adder circuit, as well as sequential circuits can be implemented using the plasmonic switches as the active elements. Moreover, the designs of the plasmonic switches and the logic operations show minimum extinction ratios greater than 20 dB, compact designs, low operating power, and high-speed operations. We combine photonics, plasmonics and electronics on the same platform to design an effective architecture for logic operations.

Highlights

Integrated photonic devices or circuits that can execute both optical computation and optical data storage are considered as the building blocks for photonic computations beyond the von Neumann architecture
Silicon photonics has emerged as a favorable field due to its capability of effective light modulation, confinement of light and compatibility, with the current complementary metal–oxide–semiconductor (CMOS) fabrication processes[5,6]
In the case of electrical triggering, either a voltage is applied across electrodes connected on both sides of a GST film or an external heater is used to change the phase of the GST27,28

Summary

Introduction

Integrated photonic devices or circuits that can execute both optical computation and optical data storage are considered as the building blocks for photonic computations beyond the von Neumann architecture. Several studies in the direction of efficient optical switches, optical modulators, and optical logic circuits have been proposed using the thermo-optic effect, the free carrier dispersion effect, and the pockels electro-optic e ffect[7,8,9,10,11,12] All these devices are volatile in nature i.e., they need continuous voltage to operate, and as a result they have high power consumption. Either an on-chip high-intensity laser pulse coupled to the waveguide containing a GST film (on-chip all-optical switching) or a laser beam focused on the GST film (free space all-optical switching) are used to heat up the material in case of optical triggering ( called self-heating)[29,30] Any of these heating mechanisms can be used in the electro-optic plasmonic switches being proposed in this paper, we have selected electrical (electrical threshold switching or thermal conduction heating) switching in our design of the plasmonic switches. One can use an external microheater or the metal in the plasmonic waveguide as a microheater to heat up the GST in case of thermal conduction heating

Methods

Conclusion