Improving super-resolution microscopy with donut-shaped light and multicolored sources
Researchers from the High-harmonic generation and EUV science group, led by Peter Kraus, have recently made two groundbreaking advances in the field of high-harmonic generation (HHG). This unlocks new potential for imaging and light generation at wavelengths up into the extreme ultraviolet (XUV), that are necessary for studying extremely small structures in the order of 100 nm with a microscope. The studies highlight innovative ways to push the limits of light-based technologies for applications ranging from super-resolution microscopy to compact XUV light sources. The research led to publications in Science Advances on November 13th and Nature Communications on September 27th.
Studying very small structures with light is typically done with very short wavelengths, preferably smaller than the relevant dimensions in the sample (around 100 nanometer). Such ultra-short wavelengths can be obtained with high-harmonic generation (HHG). In this process a light pulse with a longer wavelength is directed at a gas, where interference and non-linear optical effects cause the light to split into several higher order waves with a much shorter wavelength: the high harmonics. These high harmonics can then be used for spectroscopy of nanostructures.
In Science Advances [1], first author Kevin Murzyn and co-workers demonstrated a technique using HHG that could revolutionize microscopy by breaking the so-called Abbe diffraction limit. Traditionally, this limit defines how small a detail a microscope can resolve. It can be surpassed by techniques that rely on fluorescent labeling, but in many (biomedical) applications such labeling is undesirable. Kevin and co-workers now managed to surpass the Abbe diffraction limit using HHG. Their method involves introducing a second donut-shaped laser beam that confines harmonic generation to a smaller spatial region, achieving super-resolution imaging. This breakthrough offers the potential to see structures smaller than previously thought possible—down to sub-100 nm resolution—without the need for fluorescent labels.
Meanwhile, in Nature Communications [2], Sylvianne Roscam Abbing, Nataliia Kuzkova, and co-workers delved into the intricacies of generating high-order harmonics in more complex geometries. The team focused on increasing the efficiency of HHG in solid materials, an area where performance has often been outpaced by gas-based methods. By using a two-color non-collinear wave mixing approach in silica, they enhanced harmonic generation, even in the extreme ultraviolet (XUV) part of the spectrum. This boost in efficiency could significantly improve the signal strength in experiments like those conducted by Kevin, paving the way for more precise and faster measurements in HHG-based microscopy and other applications.
Together, these studies highlight how high-harmonic generation from solids is opening new avenues for both imaging and light-source technologies, marking a decisive step forward in the field. With the work of Murzyn et al. enabling sharper images and Roscam Abbing et al. offering a more powerful light source, researchers may soon have the tools needed for unprecedented precision in nanoscale imaging and material analysis. These discoveries could have significant implications for fields such as biology, materials science, and nanotechnology.
Do you want to know more about this research? Then contact Peter Kraus p.kraus@arcnl.nl
References:
- Sylvianne D. C. Roscam Abbing, Nataliia Kuzkova, Roy van der Linden, Filippo Campi, Brian de Keijzer, Corentin Morice, Zhuang-Yan Zhang, Maarten L. S. van der Geest, Peter M. Kraus, “Enhancing the efficiency of high-order harmonics with two-color non-collinear wave mixing in silica“, Nature Communications 15, 8335, 27 September (2024)
- Kevin Murzyn, Maarten L. S. van der Geest, Leo Guery, Zhonghui Nie, Pieter van Essen, Stefan Witte, Peter M. Kraus, “Breaking Abbe’s diffraction limit with harmonic deactivation microscopy“, Science Advances, 10, 13 November (2024).
