Design of bifunctional phase-change device for storage memories and reconfigurable metasurfaces

Abstract

Herein, we design an optoelectronic device using phase-change materials (PCMs) and assess its ability to possess two functionalities: the perfect absorption of photonic metasurfaces and the high-density storage capability of electronic memories. Both functionalities are evaluated experimentally and via simulations. Such bifunctionalities are achieved according to the phase-transformation extent of the designed hybrid that comprises a phase-change stack having Si/SiO2/Au/Ge2Sb2Te5 (GST)/indium tin oxide (ITO) and a conductive PtSi probe. The use of PCM layers either in a full crystalline or an amorphous phase causes perfect absorption. The resonant wavelength of the device can be dynamically changed by modulating the phase-change extent of the PCM layer. Generating a continuous crystalline region or separated crystalline bits inside the amorphous GST exhibits a larger tuneability of the phase-change extent than forming separated amorphous bits inside the crystalline GST, and allows for a wider bandwidth of 300 nm for perfect absorber applications. Forming amorphous bit array inside crystalline background yields discernible optical reading contrast when compared to forming a crystalline bit array. The amorphous bit array configuration has an areal density of ～500 Gbits/inch2, data rate of 5 Mbits/s, and energy consumption of 92 pJ/bit. These values render the configuration attractive for probe storage applications. Such a designed hybrid with the ability to process data photonically and store data electronically exhibit its promising for highly integrated metasurface and superb compact electro-optical computing device.