The remarkable innovations of Ursula Keller have pushed the frontiers in ultrafast science and technology by providing solid-state and semiconductor lasers with ultrashort pulse generation that are revolutionizing photonics and tremendously impacting physics, biology, and telecommunications. Keller developed the semiconductor saturable absorber mirror (SESAM) for generating ultrashort pulses, which transformed femtosecond lasers from complex devices only used by specialists to reliable instruments suitable for use in any general-purpose scientific laboratory. She has since continued to define and push the technology with world-leading experimental results that have demonstrated orders of magnitude improvement in key features such as pulse duration, energy, and average power. Her SESAM technology overcame switching instabilities that had prevented modelocking of solid-state lasers for more than two decades and demonstrated how to generate picosecond and femtosecond pulses from diode-pumped laser technology lasers in a scalable, stable, and reliable manner.

Keller also pioneered vertical external cavity surface emitting lasers (VECSELs), which provide superior beam quality even at high powers compared to other semiconductor lasers and can operate both in the continuous wave and pulsed regimes. Combining the merits of SESAM and VECSELs, Keller proposed and demonstrated a new concept for the generation of ultrashort optical pulses from an all-semiconductor laser system. The modelocked integrated external-cavity surface emitting laser (MIXSEL) enables wafer-scale integration of gain and saturable absorption that allows simple and compact ultrafast lasers to be realized with the potential for high-volume manufacturing. She led her research group to overcome extreme technical challenges to achieve a 150-fold increase in the power emitted by MIXSELs. Keller’s development of carrier phase stabilization and frequency comb technology during the 1990s was integral to Hänsch and Hall’s development of laser-based spectroscopy that garnered them the 2005 Nobel Prize in Physics.

An IEEE Fellow and recipient of the Optical Society’s Charles H. Townes Award (2015) and the 2018 IEEE Photonics Award, Keller is director of the Swiss National Centre of Competence for Research in Molecular Ultrafast Science and Technology (NCCR MUST) at ETH Zürich, Zürich, Switzerland.