JEOS-RP Celebrates Best Papers of 2025

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Published on 09 February 2026

During December 2025, the European Optical Society reflected, as usual, on the achievements of the outgoing year. The contributions made by researchers towards rapid progress in optics and photonics, through publishing papers in Journal of the European Optical Society-Rapid Publications, were numerous and notable. During this period of reflection, the Society decided to formally recognise those that were truly driving advancements in the discipline through the introduction of a Best Papers Award.

Papers that made significant impact or novel contributions were shortlisted and on the 12th December the National Optical Society Advisory Board members voted for the 5 best papers of 2025.

We are delighted to present here below the winners. As JEOS-RP is an Open Access journal, all papers are freely available to read and redistribute.

EDP Sciences, EOS and the NOS Advisory committee extend our sincere congratulations to the recipients of these awards and look forward to following the continuation of their research.

JEOS-RP Best Papers of 2025

Microsphere-assistance in conventional, interference and confocal microscopy - modeling and experimental results, Hueser, Lucie; Pahl, Tobias; Hagemeier, Sebastian; Eckhardt, Tim; Rosenthal, Felix; Diehl, Michael; Lehmann, Peter

Abstract: Topographical as well as microscopic imaging of nanoscale surfaces plays a pivotal role across various disciplines. Nevertheless, achieving fast, label-free, and accurate characterization of laterally expanded structures below the diffraction limit remains challenging. Recent studies highlight the use of microsphere assistance for resolution improvement. Confocal, conventional, and interference microscopy, augmented by microspheres, enable the imaging of small structures that were previously inaccessible. In this contribution, results of microsphere-assisted confocal and conventional bright-field microscopy (MAM) are compared to underline the decisive role of the confocal effect. Furthermore, an extensive comparison of simulated confocal results is presented to highlight the experimental results.

Commenting on their research, Lucie Hueser shared: “Connecting experimental results with the insights from simulations of the imaging process offers powerful potential to elucidate the capabilities of different imaging systems. Our findings present insights into the signal formation and lateral resolution improvement using microspheres as near-field support in conventional, interference, and confocal microscopy."

An integrated exposure and measurement tool for 5-DOF direct laser writing based on chromatic differential confocal sensing, Belkner, Johannes; Leineweber, Johannes; Hein, Georg; Stauffenberg, Jaqueline; Barth, Alexander; Kissinger, Thomas; Manske, Eberhard; Froehlich, Thomas

Abstract: Accurate and uniform fabrication of microstructures on highly curved substrates requires exposure with the waist of a focused laser beam at every point. In order to realize this, the exposure beam must be held perpendicular and focused onto the local substrate. Here we present an optical tool for our developed 5-axis nano-positioning and nano-measurement machine based on the chromatic differential confocal microscope. Thereby, we introduce the optical design methodology to realize high axial sensitivity from differential optical feedback via axial chromatic aberration. Additionally, the deflection angle is measured via a camera sensor to provide angular feedback. Overall, our probe attains a nanometer axial sensitivity and arc-minute angular sensitivity in a confined space of 50 × 80 × 36 mm3.

Corresponding author Johannes Belkner, and receiving the award, kindly shared a “behind-the-scenes” look at the equipment setup in situ.

Control of high harmonic generation in mixed gaseous media, Pablos-Marin, Jose Miguel; Serrano, Javier; Hernandez-Garcia, Carlos

Abstract: High harmonic generation (HHG) in gaseous media provides a robust method for producing coherent extreme-ultraviolet (EUV) radiation and attosecond pulses. However, the spectral and temporal properties of these pulses – such as bandwidth and chirp – are fundamentally limited by the underlying generation mechanisms. Typically, tailoring the EUV emission involves modifying the properties of the intense infrared femtosecond driving pulse, and/or the macroscopic laser-matter configuration. Here, we focus on controlling the HHG process through the gas specie, introducing mixed-gas targets as a practical approach to enhance control over the EUV harmonic radiation. Through advanced simulations assisted by artificial intelligence that take into account both the quantum microscopic and macroscopic aspects of HHG, we demonstrate how mixtures of argon and helium modulate the emitted EUV harmonics. A simple model reveals that these modulations arise from coherent interference between harmonics emitted by different species at the single-atom level, and that they can be tuned by adjusting the macroscopic relative concentrations. Furthermore, by spatially separating the gas species into two distinct jets in a symmetric configuration, we gain additional control over the whole harmonic bandwidth. This strategy provides a realistic and versatile pathway to tailor EUV light and attosecond sources via HHG, while also enabling the identification of species-specific contributions to the process. In particular, it holds potential for application in high harmonic spectroscopy, where unknown features of a gas target can be identified through the HHG spectrum generated from a mixture with a known reference gas.

The authors received this award with gratitude, commenting: “This accolade from JEOS:RP validates our advances in high harmonic generation control, opening new pathways for ultrafast optics applications."

A review of research on optical true time delay technology, An, Ting; Liu, Limin; Han, Chunhui; Zhu, Sai; Jiang, Yunfeng

Abstract: Light controlled phased array has the advantages of fast response speed, compact system, diverse functions, and flexible control, and has been widely applied in many scientific and technological fields. Optical true delay technology (OTTD) is the most direct technical means to achieve phase delay of optical carrier signals, and it is also the most basic technical means to implement optical controlled beamforming systems. In order to fully understand the optical true delay technology, this article first elaborates on the principle of phased array antennas and the reasons for beam squint, and analyzes the impact of true delay on the performance of phased array radar. Then, the basic principle, technological progress, and related applications of optical true delay are introduced. Taking four common structures of optical true delay lines as examples, which are micro-ring resonant cavity array, grating true time delay line, multi-path switchable optical true time delay line (OTTDL), and wavelength selective optical delay line, their performance in delay accuracy, adjustable delay range, and frequency bandwidth are compared. Finally, the current problems and future development trends of optical controlled beamforming technology were summarized.

Backward-wave optical parametric oscillators: principles, applications, and recent advancements,Laurell, Fredrik; Pasiskevicius, Valdas

Abstract: Backward-wave optical parametric oscillators (BWOPOs) represent a significant advancement in nonlinear optics, offering unique capabilities such as narrowband, highly stable outputs without the need for mirrors or coatings. Leveraging self-established distributed feedback, these devices exhibit exceptional spectral and spatial properties. This paper explores the principles behind BWOPOs, materials and techniques used, and their applications, particularly in mid-infrared lidar systems including CO2 monitoring. Recent developments in cascaded systems and BWOPO waveguides are highlighted, demonstrating the potential of BWOPOs to revolutionize laser technology.