Opportunities and Challenges for Large-Scale Phase-Change Material Integrated Electro-Photonics

Programmable photonics have the potential to completely transform a range of emerging applications, including optical computing, optical signal processing, light detecting and ranging, and quantum applications. However, implementing energy-efficient and large-scale systems remains elusive because commonly used programmable photonic approaches are volatile and energy-hungry. Recent results on nonvolatile phase-change material (PCM) integrated photonics present a promising opportunity to create truly programmable photonics. The ability to drastically change the refractive index of the PCMs in a nonvolatile fashion allows creating programmable units with zero-static energy. By taking advantage of the electrical control, nonvolatile reconfiguration, and zero crosstalk between each unit, PCMs can enable extra large-scale integrated (ELSI) photonics. In this Perspective, we briefly review the recent progress in PCM photonics and discuss the challenges and limitations of this emerging technology. We argue that energy efficiency is a more critical parameter than the operating speed for programmable photonics, making PCMs an ideal candidate. This has the potential for a disruptive paradigm shift in the reconfigurable photonics research philosophy, as slow but energy-efficient and large index modulation can provide a better solution for ELSI photonics than fast but power-hungry, small index tuning methods. We also highlight the exciting opportunities to leverage wide bandgap PCMs for visible-wavelength applications, such as quantum photonics and optogenetics, and for rewritable photonic integrated circuits (PICs) using nanosecond pulsed lasers. The latter can dramatically reduce the fabrication cost of PICs and democratize the PIC manufacturing process for rapid prototyping.