Stephan W. Koch

Stephan W. Koch from the Philipps University of Marburg in Germany died in Marburg on 12 September 2022 at the age of 69 after a short illness. He had recently retired as a professor of physics at the university, a position he had occupied since 1993 after spending the period of 1986–93 as a professor of optical sciences and physics at the University of Arizona. He had continued to maintain a many-decades-long collaborative link to Arizona’s Wyant College of Optical Sciences as an adjunct professor until his untimely death.

Stephan was a highly respected, pioneering theoretical physicist whose groundbreaking research on consistent many-body theory shaped the scope of optical, quantum-optical, and electronic properties of solids. He was a prolific trendsetter, as evidenced by his remarkable body of work that led to transformational insights and experimental advancements in semiconductor quantum optics, coherent ultrafast phenomena, lightwave electronics, the interface of optics and quantum transport, and laser technology. His name will always be associated with the semiconductor Bloch equations, so elegantly derived in his classic textbook coauthored with Hartmut Haug, Quantum Theory of the Optical and Electronic Properties of Semiconductors. Stephan was also a very dedicated university teacher who not only passed his enthusiasm to students but also mentored numerous scientists, now spread worldwide in academia. The Marburg school of consistent many-body theory was born and carries on Stephan’s scientific legacy.

Stephan received numerous prestigious national and international honors and awards, including the Leibniz Prize (1997), the Max Planck Research Award (1999), and Fellow of the OSA (now Optica). With Stephan’s death, we lost a very special colleague, friend, teacher, and mentor whose intense dedication has made a lasting impact on semiconductor optics. We will all miss the conversations with Stephan, his criticism and visionary ideas, as well as his tireless dedication to his group and the community. Our deepest sympathy goes out to Stephan’s wife, Rita.