Design of phase change Ge2Sb2Te5 based on-off electro-optic switch

Abstract

This is the accepted version of the paper.This version of the publication may differ from the final published version.Permanent repository link: http://openaccess.city.ac.uk/20694/ Link to published version: http://dx. ABSTRACTDesign of electro-optic ON-OFF switches based on well-known phase change material Ge 2 Sb 2 Te 5 (GST) is presented. The electro-optic switch is achieved by implementing by co-directional coupling between a 220 nm thick silicon nanowire and a silicon waveguide topped with ITO-GST-ITO layers at the 1.55μm wavelength. By introducing the electric field via the ITO electrodes, the GST layer can be changed between the amorphous and crystalline states. As the modal loss in the crystalline state is much higher than the amorphous state, through a rigorous modal analysis of the coupled silicon nanowire and GST waveguide by using the finite element method, the optimal ITO spacing is obtained at 75nm which is less sensitive to device parameter variations and thus offering better tolerances. The GST thickness is also optimized for the phase matching point at 25 nm in order to efficiently transfer power from silicon nanowire to GST waveguide to attain the OFF state. Once the device is phase matched in crystalline state, the power in the amorphous state will pass with very little interaction with the GST waveguide resulting in an ON state. The Eigenmode Expansion Method of Fimmprop is used as a junction analysis approach to calculate the optical power coupling efficiencies to the output silicon nanowire. The extinction ratio of the electro-optic switch and insertion loss in ON state at phase matching can be obtained as a function of the device length. A compact 1.75 μm long device shows a high extinction ratio of 22 dB with an insertion loss of only 0.56 dB.

Optimally designed tunable phase change material-based narrowband perfect absorber

“…Several active materials, including semiconductors, 10 diodes, 11 liquid crystals, 12 superconductors, 13 two-dimensional materials, 14 and phase change materials (chalcogenides), 15 are being investigated for reconfigurable metasurface design. The phase change chalcogenides are easily tuned using electrical 16 (Joule heating), thermal 17 (various micro-heater configurations), and optical means (also called the thermo-optic effect) 18 in addition to other methods such as electro-optic effects 19 . Among these, the optical means provide faster and accurate means of modulation for addressing individual meta-atoms 20 (using the spatially controlled laser scans 21 ).…”

“…The phase change chalcogenides are easily tuned using electrical 16 (Joule heating), thermal 17 (various micro-heater configurations), and optical means (also called the thermo-optic effect) 18 in addition to other methods such as electro-optic effects. 19 Among these, the optical means provide faster and accurate means of modulation for addressing individual meta-atoms 20 (using the spatially controlled laser scans 21 ).…”

Tunable crystallization mechanism of Sb4Te films by VO2 nano-grid framework for breaking through the trade-off between thermal stability and crystallization speed

“…More specifically, we introduced VO 2 (Vanadium dioxide) into Sb 4 Te alloy to address the issues mentioned above. VO 2 , another promising kind of phase change material, demonstrates a structural change and concomitant obvious variation of both optical and electrical properties at around 68 °C [10], but it is a volatile phase change material. It has been broadly investigated for energy storage [11] and switchable devices [12].…”