Design of practicable phase-change metadevices for near-infrared absorber and modulator applications.

Santiago García-Cuevas Carrillo,Harish Bhaskaran,Hasan Hayat,Maciej Klemm,C David Wright,Martin J Cryan,Geoffrey R Nash

doi:10.1364/oe.24.013563

Abstract

Phase-change chalcogenide alloys, such as Ge2Sb2Te5 (GST), have very different optical properties in their amorphous and crystalline phases. The fact that such alloys can be switched, optically or electrically, between such phases rapidly and repeatedly means that they have much potential for applications as tunable photonic devices. Here we incorporate chalcogenide phase-change films into a metal-dielectric-metal metamaterial electromagnetic absorber structure and design absorbers and modulators for operation at technologically important near-infrared wavelengths, specifically 1550 nm. Our design not only exhibits excellent performance (e.g. a modulation depth of ~77% and an extinction ratio of ~20 dB) but also includes a suitable means for protecting the GST layer from environmental oxidation and is well-suited, as confirmed by electro-thermal and phase-transformation simulations, to in situ electrical switching. We also present a systematic study of design optimization, including the effects of expected manufacturing tolerances on device performance and, by means of a sensitivity analysis, identify the most critical design parameters.

Highlights

Thin-film electromagnetic absorbers have a number of important applications in the infrared and visible part of the spectrum including infrared detection [1,2], solar energy harvesting [3,4] and refractive index sensing [5]
We take into account, for the first time and via a detailed optimization and tolerance analysis, the effects of manufacturing tolerances on key device performance parameters and we identify the most critical tolerances by means of a sensitivity analysis
We use in particular the modulation depth (MD) which is defined [33] as the difference between the maximum reflected power Pmax and the minimum reflected power Pmin, normalized by the incident power (Pinc), i.e

Summary

Introduction

Thin-film electromagnetic absorbers have a number of important applications in the infrared and visible part of the spectrum including infrared detection [1,2], solar energy harvesting [3,4] and refractive index sensing [5]. Chalcogenide phase-change alloys, such as (Ge2Sb2Te5) (GST), are materials whose electrical and optical properties differ very considerably between their amorphous and crystalline phases and which can be (electrically or optically) switched between such phases quickly and repeatedly This has led to their application in a variety of areas, in particular for non-volatile memory devices [9,10], and more recently for the provision of solid-state and flexible displays [11] and for the realization of new approaches to computing [12,13]. The phase-transition in VO2 is volatile (the material returning to its insulating phase on cooling), whereas in GST (and AIST etc.) it is non-volatile, meaning that any particular (amorphous or crystalline) state can be maintained without the requirement for input power – a attractive feature in terms of device performance

Objectives

Methods

Results

Conclusion