[citation needed] In September 1948, Aigrain met Claude Dugas at the Carnegie Institute of Technology who had been sent by Yves Rocard on a CNRS grant (Centre national de la recherche scientifique / Back translation: National Centre of scientific research) to work with Frederick Seitz (Head of the Physics Department).
Back in France he was assigned to the physics laboratory of the École Normale Supérieure, directed by Yves Rocard, as technical assistant to the Marine Research Center Director (1948–1949).
[citation needed] Following this he was an engineer at the Atomic Energy Commission (Commissariat à l'énergie atomique) between the years 1949-1950, then an assistant at the Collège de France (to Jean Laval, Professor of theoretical physics) from 1950 to 1951.
On 1 October 1954, he became a permanent lecturer at the University of Paris's Science Faculties for the teaching of the PCB certificate (Certificat d'études physiques, chimiques et biologiques / Back translation: Certificate of physical, chemical and biological sciences) alongside Maurice Curie, Jean-Paul Mathieu [fr] and André Guinier, then Paul Soleillet and Jean Brossel.
He obtained a senior lecturing role on 1 January 1957 and was then appointed full Professor of Electrical Engineering by 1 October 1958 after the retirement of Marcel Pauthenier.