Ultracompact CMOS-compatible optical logic using carrier depletion in microdisk resonators

Dusan Gostimirovic,Winnie N. Ye

doi:10.1038/s41598-017-12680-1

Abstract

We present a CMOS-compatible optoelectronic directed logic architecture that achieves high computational throughput (number of operations per second per unit area) by its ultracompact form factor. High speed-to-power performance is also achieved, by the low capacitance and high junction-to-mode overlap of low-radii SOI vertical pn junction microdisk switches. By using wavelength-division multiplexing and two electrical control signals per disk, each switch performs (N)OR, (N)AND, and X(N)OR operations simultaneously. Connecting multiple switches together, we demonstrate higher-order scalability in five fundamental N-bit logic circuits: AND/OR gates, adders, comparators, encoders, and decoders. To the best of our knowledge, these circuits achieve the lowest footprint of silicon-based multigigabit-per-second optical logic devices in literature.

Highlights

The billions of underlying nanoscale transistors driving modern high-performance computers have been optimized—through decades of substantial and incremental improvements—to subpicosecond switching speeds and subfemtojoule levels of energy consumption per bit[1]
Though well-performing optical logic has been reported in III-V based semiconductor optical amplifiers (SOAs)[14,15], their incompatibility with low-cost and high-density (CMOS) manufacturing puts them at a significant disadvantage
High-contrast modulation is achieved in these microresonators by shifting their transmission spectra in relation to the propagating light, through electrically induced free-carrier dispersion (FCD), two-photon absorption (TPA) based carrier dispersion[27,28], thermal effects[29], and the Kerr effect[30]

Summary

Introduction

The billions of underlying nanoscale transistors driving modern high-performance computers have been optimized—through decades of substantial and incremental improvements—to subpicosecond switching speeds and subfemtojoule levels of energy consumption per bit[1]. Vertical junction microdisks are used rather than lateral junction microrings, as the same change in depletion width spans a larger percentage of the waveguide confined mode, thereby reducing the required control voltage This junction is split in half and electrically isolated to create two independently working diodes connected to the two control inputs of a basic logic operation. This resonant photonic device acts as a filter, where most wavelengths of light propagate from the input to the through port, while wavelengths that are integer multiples of the effective path length of the disk cavity exit at the drop port. Each control has the ability to shift the transmission peak on and off resonance with the propagating optical signal(s), allowing a single switch to produce a 2-bit logical response

Objectives

Methods

Discussion

Conclusion