Professor Ursula Keller
ETH Zurich, Switzerland


Ursula Keller, a tenured professor of physics at ETH Zurich since 1993, has shaped the field of ultrafast science. She led the NCCR MUST program from 2010 to 2022. Keller obtained her Diplom from ETH in 1984 and a Ph.D. from Stanford University in 1989. Between 1989 and 1993, she worked as a Member of Technical Staff at Bell Labs, initiating her independent research career. Keller co-founded Time-Bandwidth Products, which was acquired by JDSU in 2014, and K2 Photonics in 2023. She has served on Jenoptik's supervisory board since 2022. Her research focuses on advancing ultrafast science and technology through innovations in ultrafast solid-state and semiconductor lasers. She invented the semiconductor saturable absorber mirror (SESAM) for ultrashort pulse generation in solid-state lasers resolving the long-standing Q-switching problem. She pushed pulse generation into the one to two optical-cycle regime and pioneered carrier-envelope offset stabilization, full frequency comb generation and stabilization.  Her contributions include establishing ultrafast solid-state lasers for scientific and industrial applications and inventing new multiplexing methods for dual-comb applications. Keller's pioneering work in attosecond science includes the attoclock technique, full electric field control for petahertz electronics, and groundbreaking attosecond photoemission time delays using coincidence detection and angular resolution. Her awards include the Swiss Science Prize Marcel Benoist (2022), the OSA Frederic Ives Medal (2020), the SPIE Gold Medal (2020), the IEEE Edison Medal (2019), the OSA Charles H. Townes Award (2015), the EPS Senior Prize (2011), and two ERC advanced grants. Keller has supervised 95 Ph.D. students, authored 519 journal articles, and has an h-index of 120 with over 55,000 citations according to Google Scholar. She recently authored "Ultrafast Lasers," a graduate textbook published by Springer Verlag in 2022.


Abstract:
Single-Cavity Dual-Comb Lasers: Revolutionizing Spectroscopy and Ultrafast Measurements

Since 1999, the frequency comb revolution has had a significant impact on research in frequency metrology, optical clocks, and attosecond science. More recently, dual-comb lasers have advanced both spectroscopy and ultrafast pump-probe measurements. These lasers emit two combs with slightly different pulse repetition rates, facilitating equivalent time sampling for various pump-probe measurements and interferometry for spectroscopy applications. Dual-comb lasers simplify and expedite the measurement process by eliminating the need for moving parts and complex mechanical adjustments. We pioneered single-cavity dual-comb lasers using polarization and spatial multiplexing in diode-pumped solid-state and semiconductor lasers. These innovations offer low correlated noise, greatly simplifying dual-comb measurements as no additional frequency comb stabilization is required for many applications. Demonstrated uses include IR to mid-IR spectroscopy, precise laser ranging, THz time-domain spectroscopy, and picosecond ultrasonics. Understanding the unique noise properties of single-cavity diode-pumped Yb-doped solid-state lasers enables the generation of a broadband supercontinuum with record-setting low noise in narrow spectral bands, including the spectral wings, ideally suited for hyperspectral LiDAR applications.



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