Single Carbon Nanotubes as Ultrasmall All-Optical Memories

Takushi Uda,Yuichiro K Kato,Akihiro Ishii

doi:10.1021/acsphotonics.7b01104

Takushi Uda, Yuichiro K Kato + Show 1 more

Open Access

https://doi.org/10.1021/acsphotonics.7b01104

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Abstract

Performance improvements are expected from integration of photonic devices into information processing systems, and in particular, all-optical memories provide a key functionality. Scaling down the size of memory elements is desirable for high-density integration, and the use of nanomaterials would allow for devices that are significantly smaller than the operation wavelengths. Here we report on all-optical memory based on individual carbon nanotubes, where adsorbed molecules give rise to optical bistability. By exciting at the high-energy tail of the excitonic absorption resonance, nanotubes can be switched between the desorbed state and the adsorbed state. We demonstrate reversible and reproducible operation of the nanotube optical memory, and determine the rewriting speed by measuring the molecular adsorption and desorption times. Our results underscore the impact of molecular-scale effects on optical properties of nanomaterials, offering new design strategies for photonic devices that are a few orders of magnitude smaller than the optical diffraction limit.

Highlights

O n-chip photonic devices can potentially boost the capabilities of modern information-processing systems by replacing their electrical counterparts, as they offer a number of advantages such as low power dissipation, high speed processing, and reduced crosstalk.[1]
Since environmental screening plays an important role in determining the excitonic levels,[20,21] suspended carbon nanotubes (CNTs) show a considerable modification of the transition energies even with water molecule adsorption.[22−25] Excitation-power-dependent photoluminescence (PL) emission energy has been attributed to heating-induced molecular desorption,[26,27] suggesting that optical control of CNT emission properties is possible via the adsorbed molecules
We report on optical bistability in individual carbon nanotubes, arising from excitonic resonance shifts induced by molecular adsorption and desorption

Summary

Introduction

O n-chip photonic devices can potentially boost the capabilities of modern information-processing systems by replacing their electrical counterparts, as they offer a number of advantages such as low power dissipation, high speed processing, and reduced crosstalk.[1] High-efficiency photon generation can be achieved with thresholdless lasing in nanoscale metallic cavities,[2] while terahertz modulation has been accomplished using silicon−polymer hybrid waveguides.[3] Further development toward optical computing requires advances in key devices such as all-optical memories and switches These functional devices usually employ optical bistability, where two optically distinguishable states can be selected by optical means.[4] The majority of the optical bistable devices rely on cavity effects,[5−10] since they provide strong light confinement for enhancing nonlinearity and allow miniaturization of the systems. We employ the bistability to demonstrate reversible and reproducible switching operation, and perform time-resolved measurements to determine the rewriting speed of the nanotube optical memory

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Conclusion