Ultrashort laser pulses — shorter than a millionth of a millionth of a second — have made a transformative impact on fundamental science, engineering, and medicine. However, their ultrashort duration has made them elusive and difficult to measure. About ten years ago, researchers from Lund University and Porto University introduced a tool for measuring pulse duration of ultrafast lasers. The same team has now achieved a breakthrough that allows the measurement of individual laser pulses across a wider parameter range in a more compact setup. “The current standard measurements for femtosecond lasers, typically used in industry and medicine, give just an estimate of the pulse duration. Our approach gives a more complete measurement and can contribute to unleash the whole potential of ultrafast laser technology,” said Daniel Díaz Rivas, doctoral student at Lund University. Femtosecond pulses find daily use in applications like eye surgery and micromachining in industry, and can be used to investigate energy transfer in photosynthesis and electron dynamics. Even with their widespread use, precise measurement of the pulses' shape and duration remains challenging. Electronic instruments are too slow, which has brought researchers to optical methods. The lab set-up for the new method. Courtesy of Lund University. These types of optical techniques, however, require multiple measurements in a scanning sequence, which makes them unsuitable for capturing individual pulses in real time. Single-shot versions have emerged for characterizing very short pulses commonly used in fundamental science, but they struggle with longer pulses more commonly used in industrial and medical applications. The limitations are related to the complexity of sufficiently stretching the pulses within a compact optical setup. The method developed by Lund researchers uses a simple optical principle to stretch ultrafast laser pulses. It sends a pulsed laser beam through a diffraction grating. This component spatially separates light into its colors, imaging the grating with a combination of lenses, and allows researchers to control the pulse duration across the laser beam precisely. This approach allows femtosecond pulses to be lengthened more than tenfold within a compact optical setup. This approach enables full characterization in a single shot, without the need for pre-compensation optical elements. The result of this work is a versatile technique that can work for pulse durations ranging from a few femtoseconds to hundreds, thus covering scientific, industrial and medical applications. It opens the door to real-time monitoring of individual pulses, something previously out of reach for many laser platforms. Beyond pulse characterization, this optical principle can be applied to shape the spatiotemporal properties of light pulses and explore different ways to study light-matter interactions. This research was published in Optica (www.doi.org/10.1364/OPTICA.572768).