Clara Baleine1 Yifei Zhang2 Jeffrey Chou3 Mikhail Shalaginov2 Carlos Rios2 Christopher Roberts3 Paul Robinson3 Vladimir Liberman3 Fan Yang2 Junying Li2 Myungkoo Kang4 Claudia Goncalves4 Kathleen Richardson4 Tian Gu2 Juejun Hu2

1, Lockheed Martin, Orlando, Florida, United States
2, Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
3, Lincoln Laboratory, Massachusetts Institute of Technology, Lexington, Massachusetts, United States
4, College of Optics and Photonics, University of Central Florida, Orlando, Florida, United States

Optical phase change materials (O-PCMs) have found widespread adoption in photonic switches, reconfigurable meta-optics, reflective display, and optical neuromorphic computers. Current phase change materials, such as Ge-Sb-Te (GST), exhibit large contrast of both refractive index (Δn) and optical loss (Δk), simultaneously. The coupling of both optical properties fundamentally limits the function and performance of many potential applications. We introduce a new class of O-PCMs based on Ge-Sb-Se-Te (GSST) which breaks this traditional coupling, as demonstrated with an optical figure of merit improvement of more than two orders of magnitude. The optimized alloy, Ge2Sb2Se4Te1, combines broadband, low loss transparency (1 – 18.5 μm), large optical contrast (Δn = 2.0), and significantly improved glass forming ability, enabling an entirely new range of infrared and thermal photonic devices. In this talk, we will also review an array of reconfigurable photonic devices enabled by the low-loss O-PCM, including free-space light modulators, electrically switchable and nonvolatile reconfigurable metasurfaces, and transient couplers facilitating wafer-scale device probing and characterizations.