ZOOM
DENMARk
Photonics in Denmark: building capabilities across generations
Denmark’ s photonics landscape did not emerge from a single breakthrough. From optical communications in the 1970s to today’ s strengths in specialty fibers, nanophotonics, quantum technologies and integrated photonics, its development reflects a recurring pattern: building expertise, infrastructure and industrial links around emerging technologies, then carrying those capabilities into new applications.
https:// doi. org / 10.1051 / photon / 202614018
Trishala MITRA * and Nick VOLET
Group of Integrated Photonics, Department of Electrical and Computer Engineering, Aarhus University, Aarhus, Denmark
* trish @ ece. au. dk
From cables to photons
In January 1974, DTU professor Palle Jeppesen opened an issue of Proceedings of the IEEE and encountered a technology that barely existed in Denmark: optical-fiber communication [ 1 ]. Trained in microwave electronics, he saw that expertise in electromagnetic waves and semiconductor devices could transfer to this emerging area, even if its future was uncertain.“ It was not obvious at all that it would become important,” he later recalled: coaxial cables and microwave links already worked well, while low-loss fibers and practical semiconductor lasers were still maturing [ 2 ]. Visits to Siemens and AEG-Telefunken in Germany that summer, followed by a visiting researcher from AEG-Telefunken at DTU, brought first-hand experience with fibers and semiconductor lasers into the Danish environment [ 3 ].
Optical communication was new, but long-distance communication was not. Denmark had been part of international telecommunications networks for more than a century. The Great Northern Telegraph Company, established in 1869, developed links across northern Europe and through Russia towards China and Japan. By the late nineteenth century, Denmark also had an unusually dense telephone network, while NKT, founded in 1898, became a major cable supplier to the Danish telephone companies. These established links between communications infrastructure and industry would become important as signals began moving from copper to light.
The transition happened quickly. Student projects in optical communication started at DTU in 1974 – 75, followed by a dedicated course in September 1975; all six of the first MSc graduates in the new field subsequently pursued PhDs. Industry became involved almost simultaneously. At NKT, research director Otto Gram Jeppesen saw optical fiber as both a threat to the company ' s established cable business and an opportunity. NKT embedded an engineer in the DTU environment, creating a direct bridge between academic experiments and industrial development. Collaboration with DTU ' s semiconductor laboratory then enabled Otto Leistiko to fabricate the first Danish optical fibers in 1977.
The final ingredient was a customer willing to bet on the technology. In November 1978, Jutland Telephone committed to purchasing at least 3,000 km of fiber annually for
18 www. photoniques. com I Photoniques 140