Conference Agenda

There are many fields, such as microfluidics and Organ-on-a-chip technologies, where an optimal setting and control of temperature is necessary. These fields are reaching the forefront of personalised medicine, thus requiring developing more complex systems to adequately mimic any biological condition. On this work we propose the design and fabrication of a microfluidic chip mixing Polydimethylsiloxane (PDMS) and magnetic nanoparticles (MNPs) to obtain a device whose temperature could be adjusted by means of magnetic hyperthermia. Characterization of the device was performed with confocal microscopy and microcomputed tomography (micro-CT). Magnetic hyperthermia was employed to estimate the heating curve of the devices and Computational Fluid Dynamics (CFD) simulations enabled to analyse the heat distribution within the device when introducing flow.

Differential Absorption Lidar (DiAL) method is widely used for a number of ground-based and airborne greenhouse gas measurement applications. However, for a direct detection in the 2µm range, other sources of random noise can be neglected in front of the detection noise which increases with ranging. We therefore propose to evaluate the effect of non-constant Scheimpflug-like averaging to reduce the signal-to-noise ratio along the line of sight, during a 5-hour measurement campaign in the Paris region.

This work describes the development and testing of a diagnostic technique, based on a robust setup named Point Diffraction Interferometer, to characterize the wavefronts generated by metalenses. The presented optical setup is simple, cheap and insensitive to mechanical disturbances, nevertheless precisely capable to reconstruct the radiation wavefront produced by a metalens. The obtained interference patterns exhibit suitable contrast ratio of the fringes and high spatial resolution, thus allowing the detection of even highly distorted wavefronts, and providing a measurable information about the metalens properties.

To improve the efficiency of lens blocking for grinding and polishing, plaster use was studied in the work herein reported.The dimensional stability, low thermal expansion, shapability, and cost-effectiveness of plaster can contribute to the production of high-quality optical lenses. These results foster advancements in optical manufacturing, enhancing the simultaneous processing of multiple lenses or prisms.

The further development of optical lens production is a continuous optimisation process to improve results and shorten processing times. One approach to this is the adaptation of CNC programmes to produce rotationally symmetrical spherical lenses, as well as processing with additive manufactured tools as an ultra-fine grinding step. This can enable high surface qualities with Rq roughness around 100 nm and lower.

This study approaches to turn subjective influencing factors of CNC polishing into more deterministic ones by using cerium oxide foils in a similar way to CNC grinding tools. Due to the high cerium oxide concentration of those foils, coolant lubrication is sufficient without the need of a polishing slurry, enabling polishing processes on CNC grinding machines. A surface roughness Sq ≤ 50nm could be achieved.

Ultrafast control of light-matter interactions is fundamental to mark new technological frontiers, for instance in light-driven information processing and nanoscale photochemistry. In this context, we have investigated metal-dielectric nanocavities to achieve all-optical modulation of light reflectance, ultrafast carrier dynamics at the interface between metals and semiconductors and in archetypical polaritonic systems. More recently, we have focused on nanoporous metamaterials where we observed transient plasmon-induced interband transitions, as well as anomalous ultrafast charge and spin dynamics compared to the bulk counterpart. Finally, we will show the first experimental observation of ultrafast transient grating-induced Bloch modes in hyperbolic metamaterials, pushing the boundaries of time-varying media towards optical frequencies.

The response of defects in fused silica to optical irradiation is a critical factor influencing its use in various applications. Among these defects, the non-bridging oxygen hole center (NBOHC) is one of the most extensively studied. In this work, we investigate the laser-induced formation of NBOHC defect under prolonged UV irradiation (257 nm). Photoluminescence of the induced defects provided us the possibility to study the defect formation in detail. Using a multi-transition Franck–Condon model, we accurately reproduce the PL spectra. Based on our experimental data and Franck–Condon fitting, we propose two distinct mechanisms to be responsible for the formation of NBOHC defects in fused silica.

In persistent luminescent materials, energy can be stored under irradiation by controlled traps/defects. This energy is released at ambient temperature for long time by light emission once the excitation has been stopped. The search for innovative materials with improved properties is at the heart of the work and has recently led to several new persistent luminescence materials either as nanomaterials for sensors – and in biosensing and bioimaging- or as single crystals for various applications -data storage or as jewels-. These persistent luminescent materials require identification and control of the depth of the traps and the studies of charge/discharge mechanisms

Persistent luminescence (PersL) materials can emit light long after excitation ends, making them valuable for applications in nanomedicine, security, and data storage. However, the mechanisms behind PersL remain poorly understood, hindering the development of more efficient materials. Understanding how factors like composition, doping, and optical environment influence PersL is essential. Current characterization methods, such as thermoluminescence and decay measurements, provide limited insight, especially into trapping efficiency. This study introduces a new modeling approach based on rate equations and global fitting of experimental data. It also incorporates theoretical predictions to guide novel experiments, including the first absolute measurement of persistent quantum yield (PersLQY) and a steady-state method that directly characterizes charge trapping. These innovations offer insight into trap depth distribution and the specific PersL processes occurring in materials. This comprehensive approach enables direct comparison of PersL efficiency across materials and provides a practical way to evaluate how synthesis parameters impact performance, ultimately advancing the development of next-generation PersL materials.

The optical spectroscopy of an ytterbium-doped multicomponent alkaline earth metal fluoride crystal Yb3+,Y3+:(Ca,Sr)F2 was studied with the goal of developing novel gain media for ultrafast mode-locked oscillators. The contribution of phonon-assisted (Stokes) emission to extending the gain profile beyond the range of electronic transitions was evidenced.

“Girl with a Pearl Earring”, nicknamed the Mona Lisa of the North, is considered one of Johannes Vermeer's masterpieces. The painting represents the imaginary portrait (it is a tronie) of a young woman, sublimated by the Dutch painter's masterful use of light and technical mastery. What also attracts attention in this painting, and sets it apart from other portraits, is the presence of this pearl, a presence that seems to hesitate between the brilliance of reflected light and discretion as it blends into its surroundings.

This painting and pearl dilemma can be seen as an allegory for nanoparticles in optical fibers. While the leitmotif of glass for optical fibers is to be as homogeneous as possible, optical fibers containing nanoparticles are distinguished by the deliberate introduction of heterogeneities into the glass. Induced light scattering introduces a dilemma: it must be minimized for applications such as lasers, or enhanced for sensors.

In this presentation, we will discuss the different processes for preparing optical fibers containing nanoparticles. In particular, we'll show how, thanks to the use of light (a femtosecond laser), it's possible to control the characteristics of nanoparticles in the core of optical fibers.

Optical trapping in air of dielectric micro-spheres is reported using a dual fiber optical tweezers. The spheres are trapped on the interference fringes created by the two counter-propagating optical trapping beams. The use of polarization maintaining fibers allowed us to obtain very high and reproducible trapping efficiencies.

Colour as an information carrier widely exists in nature for camouflage and signalling, inspiring recent interest in bio-inspired colour-changing materials. This study introduces an optical fibre dissipation sensor pair integrated into a soft continuum robot, allowing for dynamic colour expression in response to shape changes. The leaked light was used for real-time colour changes to interact with environmental changes. The system successfully demonstrated colour mixing and transitions during bending, offering combined sensing and visual signalling for applications for visual strain expression.

In this work, we present a novel method to accurately retrieve

temperature information from two LPGs arranged in sequence within a Mach-

Zehnder interferometric configuration. By carefully analysing specific spectral

features and formulating the inversion problem in an unconventional way, we

successfully separate the contributions of each grating, enabling reliable sensing

performance.

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For the purpose of Automatic Differentiation 3D imaging, a method which is simultaneously reliable and computationally performant is highly desired.

Most methods to solve Maxwell’s equations are either poorly performant, or numerically unstable. One method which has broken this dichotomy is the modified Born series (MBS) by Vellekoop et al.. This method formulates a simple iteration which stably converges without sacrificing per-iteration performance. However, in the case of highly-scattering materials, the iteration must be altered to ensure convergence, generally degrading the convergence rate.

After studying the modified Born series, we derived a new variant iteration, making use of a Cayley transform to guarantee stability regardless of scattering strength. Beside this improved stability being desireable in and of itself, this property can be leveraged to potentially outperform the modified Born series, in cases of scattering from strongly-scattering media.

Extreme ultraviolet (EUV) or soft X-ray scatterometry is a powerful technique enabling contactless non-destructive structural characterization of patterned nano-stacks with down to sub-nanometer precision1. The technique requires coherent EUV / soft X-ray radiation and is thus typically limited to a synchrotron or free-electron laser facilities. With the continual improvement of table-top high-harmonic-generation (HHG) sources over the last few decades, this approach has become feasible in a lab-scale environment. Here we present EUV scatteromertric results obtained using the coherent 92 eV HHG source in imec’s AttoLab on grating-type samples highly relevant for semiconductor industry. Roughness characterization was performed via direct detection of scattered light utilizing a synthetic aperture and high-dynamic-range detection coupled with noise suppression techniques. Structural parameters (CD, pitch, height, angles, layer and interlayer diffusion thicknesses) were obtained by fitting the sample model to match simulated diffraction patterns to the experimental ones. The latter were acquired through a wide angular scanning (ranging 0 to 65° from grazing). The simulated patterns were calculated by propagating light (using JCMsuite software) through a model of the structured sample. The results demonstrate sub-nanometer precision and are in good agreement with AFM and TEM measurements.

Accurate surface measurements are crucial for industrial applications. Multiwavelength digital holography (MDH) is a cutting-edge technology that extends the range of holographic measurement to the mesoscopic scale while maintaining sub-micron axial accuracy. MDH achieves this by digitally "beating" precisely measured phasers at two wavelengths to create phase maps at longer wavelength scales. However, laser mode instability and wavelength uncertainty can cause errors in the scaling factor. This leads to misestimations and unwanted phase jumps in the heightmap. Therefore, MDH typically requires highly stable lasers.

Our algorithm addresses this problem by detecting wavelength shifts during post-processing. It uses the residuals in the spatial frequency of the phasers that arises due to the misestimation of wavelength to compensate for the scaling factors and synthetic phase maps. This ensures an accurate, phase-jump-free heightmap. We find this technique essential for making MDH viable with environmental wavelength shifts and more affordable laser sources while maintaining accuracy and precision.

Microscopy with table-top high-harmonic generation (HHG) sources enable high-resolution imaging with excellent material contrast, due to the short wavelength and numerous element-specific absorption edges available in this spectral range. However, accurate characterization of dispersive samples in terms of composition and thickness remains challenging due to the limitations of lens-based optics in this spectral range. Here, we performed spectrally resolved lensless imaging using multiple high harmonics. The diffractive shearing interferometry reconstruction serves as a foundational step for element-sensitive metrology, while ptychographic reconstruction enabled the retrieval of high-precision spectral imaging and quantitative thickness mapping. Our non-destructive method offers a powerful tool to extract both the material composition and layer thicknesses of complex nanostructured samples.

Ultra-confined Light and Ultra-Strong Coupling Regime with phonon polaritions

Microscale coherent light sources are fundamental to photonic technologies, enabling applications in metrology, data processing, and high-speed computation. Photonic chips that integrate both gain and passive sections are poised to revolutionize optical communications by reducing system complexity and supporting logic operations at higher bandwidths and spped. Organic materials offer a compelling platform for these applications due to their rich optical transitions, mechanical flexibility, and chemical compatibility, making them ideal candidates for multifunctional soft photonics.

In this work, we investigate light-harvesting supramolecular complexes, characterized by strong absorption and extensive exciton delocalization, as antenna systems coupled with acceptor dyes to enhance light–matter interaction within optical microcavities.

Dye aggregates embedded in polymer matrices, confined between metal mirrors to form optical microcavities, exhibit clear polariton signatures characterized by large Rabi splitting energies, as demonstrated by angular-resolved transmittance and fluorescence measurements. This study demonstrates the potential of organic microcavities for advanced optoelectronic applications, particularly in enhancing energy transfer between distinct molecular species. Ongoing research aims to extend these findings through the integration of biological and nanostructured materials, broadening the scope of organic polaritonics and hybrid light-harvesting technologies.

Magnons and plasmons are different collective modes, involving the spin and charge degrees of freedom, respectively. Formation of hybrid plasmon–magnon polaritons in heterostructures of plasmonic and magnetic systems faces two challenges, the small interaction of the electromagnetic field of the plasmon with the spins, and the energy mismatch, as in most systems plasmons have energies orders of magnitude larger than those of magnons. We show that graphene plasmons form polaritons with the magnons of two-dimensional ferromagnetic insulators, placed up to to half a micrometer apart, with Rabi splittings in the range of 100 GHz (dramatically larger than cavity magnonics). This is facilitated both by the small energy of graphene plasmons and the cooperative super-radiant nature of the plasmon–magnon coupling afforded by phase matching. We show that the coupling can be modulated both electrically and mechanically, and we propose a ferromagnetic resonance experiment implemented with a two-dimensional ferromagnet driven by graphene plasmons.

Composite electronic excitations such as polarons and excitons, play a crucial role in the optical response of quantum materials. However, the complex underlying physics of their quasiparticles, and in particular excitons often makes it challenging to measure or infer key excitonic parameters directly from experiments. In recent years, Hamiltonian learning is an emerging approach in physics that combines theoretical modeling with machine learning algorithms to extract physical parameters from experimental data. Here, we investigate the use of Hamiltonian learning to infer excitonic parameters in one-dimensional systems. We perform exact many-body simulations of interacting models featuring excitons, demonstrating their real-time dynamics. The results will be used for training machine learning models to learn the mapping between observable quantities and underlying physical parameters. Once trained, these models will be used to infer excitonic parameters in more general systems. Ultimately, this strategy can be extended to capture more complex optical excitations phenomena, including doublons, trions, and biexcitons. This work will pave way to perform Hamiltonian learning from the dynamics of composite electronic excitations, combining quantum many-body methods, machine learning and experimental observables in quantum materials.

Chirality-driven spin configurations hold great potential for advancing spintronics by enabling compact, energy-efficient memory devices and high-density data storage solutions. Here, we will present our experimental results of spin structures in 2D van der Waals magnet. These spin configurations exhibit distinct optical characteristics, arising from spin interactions influenced by external magnetic fields and thermal variations. The observed chiral optical responses serve as a highly sensitive probe for detecting non-collinear spin arrangements. Our findings highlight 2D magnetic materials and their heterostructures as promising candidates for reconfigurable spin-photonics and spintronic applications.

Surpassing the diffraction limit has become daily practice in the field of microscopy. This is made possible by methodological breakthroughs in which specific modifications to the optical hardware and labeling biochemistry are combined with computational advances in an integral approach. In the presentation, I will give an overview of current developments in our lab at Delft University of Technology. Topics that will be presented range within limitations imposed by noise, advances for large field or volume of view, and efforts toward cryogenic microscopy. Specifically I will highlight:

(1) Recent results on the classical Richardson-Lucy deconvolution method, in which we use a Cramer-Rao Lower Bound analysis to show that amplification of noise and ill-convergence are a necessary consequence of the method.

(2) The impact of field dependent aberrations, where we use so-called Nodal Aberration Theory to model and fit field-dependent aberrations from single-molecule data, and show how this improves the accuracy of localization.

(3) Cryogenic 4pi-microscopy, where we use the self-interference of fluorescent light collected trough two opposing objective lenses, in order to overcome the poor axial localization precision in low NA localization inherent to cryogenic setups.

Structured illumination microscopy (SIM) is a powerful super-resolution technique that relies on patterned light to surpass the diffraction limit. However, conventional SIM setups require complex optical configurations that limit their adaptability and usability. In this work, we present an integrated optical chip fabricated using femtosecond laser micromachining, designed to simplify the generation of structured light. This chip, coupled with an optical fiber, enables direct generation of structured illumination on its surface, where the biological samples can be positioned for imaging. Our approach eliminates bulky optics, enhances system stability, and offers a compact and scalable solution for super-resolution microscopy. We present the design, the fabrication process, and the first validations of this system for advanced biological imaging.

Live-cell imaging enables observation of dynamic cellular processes, yet many subcellular structures remain inaccessible due to the diffraction limit. Fluctuation-based super-resolution techniques overcome this barrier by exploiting intensity variations caused by fluorescence blinking. Among these methods, Super-resolution Optical Fluctuation Imaging (SOFI) enhances spatial resolution by leveraging the statistical properties of blinking fluorophores, achieving an n-fold resolution gain through nth-order calculations. However, SOFI requires the acquisition of hundreds of frames and substantial post-processing, making it unsuitable for real-time visualization of rapid cellular dynamics.

To address these limitations, we utilize a recurrent neural network (RNN) model, MISRGRU, inspired by SOFI. MISRGRU processes sequences of low-resolution frames to extract correlated temporal signals, effectively enhancing temporal resolution while achieving a twofold increase in spatial resolution. We also compare this approach with a widely adopted fully convolutional architecture, the U-Net, evaluating both in terms of resolution enhancement and computational latency. While both models achieve comparable resolution improvements using significantly fewer frames than SOFI, the U-Net’s requirement for frame interpolation prior to inference limits its suitability for real-time applications. In contrast, MISRGRU offers a 250-fold reduction in reconstruction latency, demonstrating strong potential for real-time super-resolution imaging in live-cell experiments.

Super-resolution microscopy based on the localization of single molecules facilitates the visualization of cellular structures at a resolution approaching the molecular level. However, their low-throughput nature hampers their applicability in biomolecular research and screening. Here, we propose an efficient workflow, starting with the scanning of large areas using fast fluctuation-based imaging, followed by single-molecule localization microscopy of selected cells. We exploit the versatility of DNA oligo hybridization kinetics with DNA-PAINT probes to tailor the fluorescent blinking toward high-throughput and high-resolution imaging. Additionally, we employ super-resolution optical fluctuation imaging (SOFI) to analyze statistical fluctuations in the DNA-PAINT binding kinetics, thereby tolerating much denser blinking and facilitating accelerated imaging speeds. We demonstrate 30–300-fold faster imaging of different cellular structures compared to conventional DNA-PAINT imaging, albeit at a lower resolution. Notably, by tuning the image medium and data processing, we can flexibly switch between high-throughput SOFI (scanning an FOV of 0.65 mm × 0.52 mm within 4 min of total acquisition time) and super-resolution DNA-PAINT microscopy and thereby demonstrate that combining DNA-PAINT and SOFI enables one to adapt image resolution and acquisition time based on the imaging needs. We envision this approach to be especially powerful when combined with multiplexing and 3D imaging.

We present a method to generate vector beams using a single spatial light modulator (SLM) for depletion-based super-resolution microscopy techniques such as STED, RESOLFT, and subtraction microscopy. We demonstrate the generation of circularly polarized Laguerre-Gaussian LG01 beams and vector beams with spatially varying polarization, such as azimuthal beams. Their intensity profiles, polarization distributions, and robustness to optical aberrations are experimentally analyzed under low- and high-numerical aperture conditions to assess their suitability for super-resolution applications.