Our journey with Prof. Gabriel Popescu in quantitative phase imaging: in memoriam

Prof. Gabriel "Gabi" Popescu was a faculty member and the director of the Quantitative Light Imaging (QLI) Laboratory at the University of Illinois at Urbana-Champaign. He was a pioneer in quantitative phase imaging (QPI), having developed several common-path QPI methods at MIT and Illinois, and promoted the applications of QPI across different domains. Tragically, Prof. Popescu passed away on June 16, 2022, in Prundu, Romania. His untimely loss is deeply felt by the scientific community and his colleagues, students, and friends around the world. As former members of his group and close friends, we recount our academic journeys with Gabi in QPI from different perspectives.