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). He was working on the physics of germanium transistors. 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. Then he went back to engineering at the Atomic Energy Commission from 1951-1952. At the age of 26 in 1950, Aigrain obtained a Ph.D. in Physics from the Faculty of Science at the University of Paris. He created a small research team in the physics laboratory of the École normale supérieure with Claude Dugas to conduct research on semiconductors which went on to become the school's laboratory for solid-state physics, he would go on to lead this team until 1965. It is here where Pierre-Gilles de Gennes studied for his graduate degree. In 1952, aged 28, he resigned from the French Navy and became a temporary lecturer in theoretical physics at the Science Faculty of the University of Lille, all while remaining attached to the Physics Department at the École normale supérieure where he was also lecturing between 1952-1953. 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, 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. By 1 October 1963, Aigrain was transferred to the Atomic Energy Department. Furthermore, in 1955 he participated in the establishment of the third cycle of solid-state physics with Jacques Friedel and André Guinier, and in atomic and statistical physics with Jean Brossel, Alfred Kastler, Jacques Yvon, Pierre-Gilles de Gennes and Claude Cohen- Tannoudji. ==Works==