Highly efficient and compact

Lasers that emit extremely short light pulses are highly precise and are used in manufacturing, medical applications, and research. The problem: efficient short-pulse lasers require a lot of space and are expensive. Researchers at the University of Stuttgart have developed a new system in cooperation with Stuttgart Instruments GmbH. It is more than twice as efficient as previous systems, fits in the palm of a hand, and is highly versatile. The scientists describe their approach in the journal Nature. (DOI: 10.1038/s41586-025-09665-w)

Eighty percent efficiency is possible

“With our new system, we can achieve levels of efficiency that were previously almost unattainable,” says Prof. Harald Giessen, Head of the 4th Physics Institute at the University of Stuttgart. Through their experiments, the researchers demonstrated that achieving 80% efficiency with a short-pulse laser is fundamentally possible. This means that 80% of the power input can actually be used. “For comparison: current technologies achieve only about 35%—which means they lose much of their efficiency and are correspondingly expensive,” explains Giessen.

A lot of energy in an extremely short time

Short-pulse lasers generate light pulses that last only nano-, pico-, or femtoseconds (i.e., a few billionths to quadrillionths of a second). This allows them to concentrate a large amount of energy on a small area within an extremely short time. A pump laser and the laser that emits the short pulses work together. The pump laser supplies a special crystal with light energy. This crystal is the core of the process and transfers the energy from the pump laser to the ultrashort signal pulse. This converts the incoming light particles into infrared light. This makes it possible to carry out experiments, measurements, or production processes that are not possible with visible light. Short-pulse lasers are used in production—for example, for precise and gentle material processing. They are also used in medical technology for imaging processes or in quantum research for particularly precise measurements at the molecular level.

Synchronize laser amplification and bandwidth

“Designing short-pulse lasers efficiently remains an unsolved challenge,” explains Dr. Tobias Steinle, lead author of the study. “In order to generate short pulses, we need to amplify the incoming light beam and cover a wide range of wavelengths.” Until now, it has not been possible to combine both properties simultaneously in a small and compact optical system.” Laser amplifiers with a wide bandwidth require special crystals that are particularly short and thin. Efficient amplifiers, on the other hand, require especially long crystals. Connecting several short crystals in series is one possible way to combine both. It is already being pursued in research. The key is to ensure that the pulses from the pump laser and the signal laser remain synchronized.

New multipass concept

Researchers have now solved this problem with a new multipass procedure. Instead of using a single long crystal or many short crystals, they use a single short crystal and repeatedly run the light pulses through this crystal in their optical parametric amplifier. Between two passes through the crystal, the separated pulses are precisely realigned so that they remain synchronized. The system can generate pulses shorter than 50 femtoseconds, occupies only a few square centimeters, and consists of just five components.

Highly versatile

“Our multipass system demonstrates that extremely high efficiencies need not to come at the expense of bandwidth,” explains Steinle. “It can replace large and expensive laser systems with high power losses, which were previously required to amplify ultrashort pulses.” The new system is highly versatile and can be adapted to other wavelength ranges beyond infrared light as well as to different crystal systems and pulse durations. With this concept, the researchers aim to build small, lightweight, compact, portable, and tunable lasers capable of precisely adjusting wavelengths. They see potential areas of application in medicine, analytics, gas sensor technology, and environmental research.

On the study:

Jan Naegele, Tobias Steinle, Johann Thannheimer, Philipp Flad, and Harald Giessen
Dispersion-engineered multipass optical parametric amplification

Nature 647, 74–79 (2025).
https://doi.org/10.1038/s41586-025-09665-w

The study was supported by the Federal Ministry of Research, Technology and Space (BMFTR) as part of the KMU-Innovativ funding line, the Federal Ministry for Economic Affairs and Energy (BMWE), the Baden-Wuerttemberg Ministry of Science, Research and the Arts, the German Research Foundation (DFG), the Carl Zeiss Foundation, the Baden-Wuerttemberg Foundation, the Center for Integrated Quantum Science and Technology (IQST), and the Innovation Campus Mobility of the Future (ICM). It was carried out by the 4th Physics Institute of the University of Stuttgart in cooperation with Stuttgart Instruments GmbH as part of the MIRESWEEP project (a novel, cost-effective tunable mid-infrared laser source for analytical applications).