In 2002, he joined Massachusetts Institute of Technology as a postdoctoral researcher under the supervision of Michael Stephen Feld.
[1][2] In 2007, Popescu joined the University of Illinois Urbana-Champaign as an assistant professor and established the Quantitative Light Imaging (QLI) Laboratory.
[2] On June 16, 2022, Popescu died in his native village of Prundu, after suffering a fatal motorcycle accident.
He was survived by his wife Catherine Best-Popescu, a research assistant professor at University of Illinois Urbana-Champaign, and two children.
He has been regarded as a pioneering figure in quantitative phase-contrast microscopy, which facilitates non-destructive and label-free imaging of biological samples.