The University of Southampton
University of Southampton Institutional Repository

Femtosecond multi-level phase switching in chalcogenide thin films for all-optical data and image processing

Femtosecond multi-level phase switching in chalcogenide thin films for all-optical data and image processing
Femtosecond multi-level phase switching in chalcogenide thin films for all-optical data and image processing
We report on the non-volatile switching of amorphous chalcogenide glass thin films to the crystalline phase through a through a number of reproducible, discrete, optically distinguishable intermediate states, and on the re-amorphization of these films using femtosecond laser pulses. Potential applications lie in high-base (>binary) all-optical signal modulation, high-density data storage, image processing and non-Von Neuman computing. Chalcogenide phase-change media such as Ge2Sb2Te5 (GST) are commercially established as a platform for both optical and electronic data storage (re-writable CDs, DVDs and Blu-Ray discs; Phase-change RAM). These technologies harness non-volatile amorphous-crystalline (binary) transitions in the chalcogenide induced by nanosecond optical or electronic excitations, which have also recently been applied to the realization of metamaterial electro- and all-optical transmission/reflection modulators for near- to mid-IR wavelengths providing switching high-contrast in device structures only a fraction of a wavelength thick. But chalcogenides offer a much richer pallet of transitional behaviours that can be exploited to enhance all of these functionalities and to open up new computational and image processing paradigms: They retain a 'memory' of sub-threshold excitations, such that transitions ordinarily initiated by single excitation pulses can be reproducibly stimulated by sequences of arbitrarily timed shorter/lower energy pulses cumulatively delivering the required energy.
Here we demonstrate multi-level switching of GST films down to 30 nm thick using femtosecond optical pulses. Domains ranging in size from 200 down to 1 µm2 are progressively converted through at least eight distinct partially crystalline states using 85 fs pulses. Intermediate states are distinguished and their progressively changing optical properties characterised using white light reflectivity, transmission/reflection microspectrophotometry and spectroscopic ellipsometry measurements.
Applications potential is demonstrated to high-density data storage - encoding/read-out of multiple bits per (semi-)crystalline mark with micron-level pixellation, the performance of optical arithmetic operations, and progressive tuning of chalcogenide hybrid metamaterial resonances
Wang, Q.
55f8a112-bd52-4444-a5ba-88f920bd9a75
Maddock, Jonathan
7a64744f-cd7c-4c6a-b584-af266dd08da5
Mills, B.
05f1886e-96ef-420f-b856-4115f4ab36d0
Craig, C.
2328b42b-552e-4a82-941d-45449e952f10
Rogers, E.T.F.
b92cc8ab-0d91-4b2e-b5c7-8a2f490a36a2
MacDonald, K.F.
76c84116-aad1-4973-b917-7ca63935dba5
Hewak, D.W.
87c80070-c101-4f7a-914f-4cc3131e3db0
Zheludev, N.I.
32fb6af7-97e4-4d11-bca6-805745e40cc6
Wang, Q.
55f8a112-bd52-4444-a5ba-88f920bd9a75
Maddock, Jonathan
7a64744f-cd7c-4c6a-b584-af266dd08da5
Mills, B.
05f1886e-96ef-420f-b856-4115f4ab36d0
Craig, C.
2328b42b-552e-4a82-941d-45449e952f10
Rogers, E.T.F.
b92cc8ab-0d91-4b2e-b5c7-8a2f490a36a2
MacDonald, K.F.
76c84116-aad1-4973-b917-7ca63935dba5
Hewak, D.W.
87c80070-c101-4f7a-914f-4cc3131e3db0
Zheludev, N.I.
32fb6af7-97e4-4d11-bca6-805745e40cc6

Wang, Q., Maddock, Jonathan, Mills, B., Craig, C., Rogers, E.T.F., MacDonald, K.F., Hewak, D.W. and Zheludev, N.I. (2014) Femtosecond multi-level phase switching in chalcogenide thin films for all-optical data and image processing. SPIE Photonics Europe: Metamaterials, Belgium. 14 - 17 Apr 2014.

Record type: Conference or Workshop Item (Poster)

Abstract

We report on the non-volatile switching of amorphous chalcogenide glass thin films to the crystalline phase through a through a number of reproducible, discrete, optically distinguishable intermediate states, and on the re-amorphization of these films using femtosecond laser pulses. Potential applications lie in high-base (>binary) all-optical signal modulation, high-density data storage, image processing and non-Von Neuman computing. Chalcogenide phase-change media such as Ge2Sb2Te5 (GST) are commercially established as a platform for both optical and electronic data storage (re-writable CDs, DVDs and Blu-Ray discs; Phase-change RAM). These technologies harness non-volatile amorphous-crystalline (binary) transitions in the chalcogenide induced by nanosecond optical or electronic excitations, which have also recently been applied to the realization of metamaterial electro- and all-optical transmission/reflection modulators for near- to mid-IR wavelengths providing switching high-contrast in device structures only a fraction of a wavelength thick. But chalcogenides offer a much richer pallet of transitional behaviours that can be exploited to enhance all of these functionalities and to open up new computational and image processing paradigms: They retain a 'memory' of sub-threshold excitations, such that transitions ordinarily initiated by single excitation pulses can be reproducibly stimulated by sequences of arbitrarily timed shorter/lower energy pulses cumulatively delivering the required energy.
Here we demonstrate multi-level switching of GST films down to 30 nm thick using femtosecond optical pulses. Domains ranging in size from 200 down to 1 µm2 are progressively converted through at least eight distinct partially crystalline states using 85 fs pulses. Intermediate states are distinguished and their progressively changing optical properties characterised using white light reflectivity, transmission/reflection microspectrophotometry and spectroscopic ellipsometry measurements.
Applications potential is demonstrated to high-density data storage - encoding/read-out of multiple bits per (semi-)crystalline mark with micron-level pixellation, the performance of optical arithmetic operations, and progressive tuning of chalcogenide hybrid metamaterial resonances

Text
6213.pdf - Other
Download (104kB)

More information

Published date: 2014
Venue - Dates: SPIE Photonics Europe: Metamaterials, Belgium, 2014-04-14 - 2014-04-17
Organisations: Optoelectronics Research Centre

Identifiers

Local EPrints ID: 365895
URI: https://eprints.soton.ac.uk/id/eprint/365895
PURE UUID: 8a528537-71df-4cd5-b352-f0b818931adf
ORCID for B. Mills: ORCID iD orcid.org/0000-0002-1784-1012
ORCID for C. Craig: ORCID iD orcid.org/0000-0001-6919-4294
ORCID for K.F. MacDonald: ORCID iD orcid.org/0000-0002-3877-2976
ORCID for D.W. Hewak: ORCID iD orcid.org/0000-0002-2093-5773
ORCID for N.I. Zheludev: ORCID iD orcid.org/0000-0002-1013-6636

Catalogue record

Date deposited: 23 Jun 2014 13:27
Last modified: 10 Dec 2019 01:56

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×