Costas M. Soukoulis, a pioneer and leader in the fields of localization of light, photonic crystals, three-dimensional photonic bandgap materials, and optical metamaterials, passed away at the age of 73 on 14 March 2024 in Ames, Iowa, USA.

Costas Soukoulis in his office in Ames, USA, taken in April 2011. Credit: Thomas Koschny/Ames National Laboratory

For decades, it seemed that Soukoulis was constantly travelling the world, being at conferences, giving talks, visiting many old friends, making many new friends abroad and simultaneously entertaining two very active research groups, one in the USA at Ames Laboratory and one in Crete at IESL-FORTH. “Is he at Ames?”; “No, I heard somebody saw him in Greece.”; “No, he is rather again at Karlsruhe on his Alexander von Humboldt Prize…” Often he travelled together with his beloved wife Angela, even more so giving you the feeling of being part of a warm-hearted family, in which good science and good life are inseparable.

Soukoulis was born in Agios Ioannis at Corinthia, a small village 50 miles from Athens, Greece on 15 January 1951. After obtaining his bachelor’s degree in physics from the University of Athens, he moved to the USA and obtained his master’s degree in 1975 and PhD in 1978 from the University of Chicago. He was a visiting assistant professor at the Department of Physics of the University of Virginia from 1978–1981 and then a research physicist at Exxon Corporate Research Laboratory from 1981–1984, before joining Iowa State University and Ames Lab in Iowa. He was also an associated member of IESL-FORTH at Heraklion, Crete, Greece from 1984 onwards.

At Exxon, together with Eleftherios N. Economou, he published early pioneering work on the localization of light in disordered media1,2,3. After accepting a professorial position at Ames Laboratory in 1984, he continued along this line of research4. Soukoulis and his collaborators were excited about the idea of man-made periodic architectures possessing a complete bandgap for light in three dimensions5. At that time, it was not at all clear whether such an analogy to electrons in semiconductors really worked because light is a vector wave, while electrons are simpler scalar waves. It took some more years until these ground-breaking conceptual ideas were brought to a point at which experimental realization through layer-by-layer manufacturing approaches came into reach6. Unfortunately, Soukoulis can no longer tell you his emotional version of the bumpy publication history of this famous paper on what is now well-known as the “woodpile photonic crystal”6. Ten years later, it led us to joint experiments7 and then after another ten years to the realization of the original dream of visible-frequency three-dimensional complete bandgap woodpile photonic crystals8.

In parallel, Soukoulis made ground-breaking contributions to the then emerging field of optical metamaterials. In 2004, the race to bring magnetic resonant responses and thereby negative refractive indices to visible frequencies had just started9. In yet another fruitful theory–experiment collaboration, we jointly succeeded in reaching the visible10,11. Soukoulis continued to make significant contributions to metamaterials research until very recently, including important theoretical developments on active-gain metamaterials12, chiral metamaterials13, graphene-based metamaterials14 and many others.

Being with Soukoulis made you appreciate how important good life and good science are. He could tell you that the fish served in the restaurant was caught yesterday rather than today — and the same applied to journal papers. He loved organizing conferences and knew how to create a warm welcoming atmosphere. Soukoulis once shared with us his criteria to choose invited speakers: “Firstly, I choose the best scientists, as to ensure top quality of lectures; second, the best dancers, or people who can drive dancing, as to ensure excellent social events.” Indeed, music and dance were a tradition in the conferences he organized — of course including Soukoulis dancing himself.

Soukoulis, an outstanding scientist and human, will be dearly missed by his wife Angela, their son Victor, the large “Soukoulis family” around the world, and the photonics community.