Cosmin-Constantin Popescu

Cosmin-Constantin Popescu is a Senior Staff Engineer at 2 Pi Inc. in Cambridge, Massachusetts, USA, where he works on the development of advanced optical metasurfaces for commercial photonic applications.

Popescu received his B.S. and M.S. degrees in Materials Science and Engineering from Drexel University in Philadelphia, Pennsylvania, completing the degrees in 2020 as part of an accelerated program under the supervision of Prof. Steven May. He earned his Ph.D. in Materials Science and Engineering from the Massachusetts Institute of Technology in 2025, where he conducted research in optical phase change materials-based devices under the guidance of Prof. Juejun Hu.

Prior to joining 2 Pi Inc., Popescu briefly served as a research specialist at MIT during the summer of 2025. Earlier in his career, he participated in the co-op program at Drexel University, including a position at Johnson Matthey in Wayne, Pennsylvania, 2019, where he worked on product development for diesel engine emission catalysts.

He has co-authored 20 peer-reviewed publications, including six as a first author, which have collectively received over 900 citations and resulted in an h-index of 12. He is also an inventor on one patent. His research has focused on phase-change materials, chalcogenide glasses, metasurfaces, and integrated photonic devices. His work published in Small Science was recognized as an Editor’s Choice article, and his publication in Advanced Materials received the 2024 H.J.E. Reid Award from NASA for outstanding scientific research publications. He has also presented his work at the ACerS GOMD in 2022.

Currently, he is focused on developing metasurfaces for commercial applications, combining materials engineering with a focus on reliability and optical device design for advanced optical solutions.

Abstract Title: Phase-change metasurfaces with 2D pixel-level addressability

We report a phase-change-material (PCM) based spatial light modulator that enables the first fully 2D pixel-level addressable metasurface through wafer-scale PCM integration. Metasurfaces are artificial materials composed of dense arrays of subwavelength scatterers whose collective response defines
macroscopic wavefront shaping; however, existing active metasurfaces are largely limited to global tuning of the entire surface or, at best, independent control along a single spatial dimension. Achieving true 2D addressability requires simultaneous materials uniformity, thermal confinement, and electrical isolation across
dense arrays, which has remained a central bottleneck. By integrating chalcogenide PCMs with thin-film heaters and metasurface pixels in a foundry backend-compatible architecture, this work demonstrates localized, reversible phase transformations that independently program each pixel across a 2D array. We
elucidate how PCM composition, film thickness, crystallization kinetics, and thermal distribution govern optical contrast, switching uniformity, and cycling stability, achieving the highest endurance reported to date for PCMbased metasurfaces. The realization of a truly 2D addressable metasurface is significant because it realizes
programmable optical metasurfaces capable of arbitrary spatial modulation, enabling adaptive wavefront control, beam shaping, and large-area reconfigurable photonic systems