Conference Agenda

We present a maximum-likelihood estimation (MLE) framework tailored to event-driven detectors to perform computational image reconstruction and phase retrieval. Using Poissonian photon statistics, we built an event-based loss function that maximizes the probability of having the set of events and non-events given the initial parameters. Our loss function can be utilized in both optical and electron ptychography. We demonstrate experimental reconstructions using data acquired with a Timepix3 detector.

We apply the phase triplicator profile to a phase-only hologram to generate three equally intense harmonic orders, yielding a direct version and an inverted complex conjugated version of the target pattern in the ±1st orders, and a delta function in the DC zeroth order. When combined with another identical phase-only target function, the resulting hologram yields convolution and correlation in the ±1st orders, and the target function in the zero-order. Experimental results obtained with a high-resolution liquid-crystal phase-only spatial light modulator (SLM) demonstrate the proposed design.

Since typical reflectivity studies collect intensities, we initiate 2D position-resolved interferometry to obtain phase. On gold pads and thin 3D opal photonic crystals we obtain reproducible phase steps, revealing steps even between different crystal orientations.

We demonstrate an efficient approach for correcting spatially varying (anisoplanatic) aberrations in digital holographic imaging by leveraging a Zernike-Fourier domain representation. The imaging operator was modelled in a matrix form as a combination of Fourier basis functions and Zernike decomposed field-dependent wavefront aberrations. The single-step matrix multiplication greatly reduces computational complexity compared to traditionally relying on explicit matrix inversion or point-wise convolution.

A new class of partially coherent light sources characterized by a cross-spectral density (CSD) function that depends only on a single complex variable has been recently introduced. It has been shown that the CSD of these sources is expandable in power series in their convergence domain and has vortex fields as modes. This enables the generation of a virtually unlimited number of source models with specific coherence structures. In this work, the propagation in the Fresnel region of the field radiated by uni-variable sources is analyzed. Several examples are developed to show the rich variety of behaviors that can be found.

Optical vortices are of interest in the infrared range for applications in the fields of optical fiber communications and femtosecond laser pulses. Among the current techniques used to generate optical vortices, the use of a Spatial Light Modulator (SLM) stands out. However, SLMs are expensive devices, they present a low damage threshold and do not allow the development of compact systems. A solution to this is to record a Holographic Optical Element (HOE) with the interference of two beams, one of them carrying an optical vortex. Available holographic recording materials, such as photopolymer and dichromated gelatin, are only sensitive to visible light. Thus, the recording parameters need to be optimized for reconstruction with a different wavelength. In this contribution, we explore the use of HOEs to generate optical vortices with infrared light, and present experimental results with commercial recording materials that validate the viability of the method.

Experiments whose data are processed using a computational model are often plagued by uncertainties in the experiment which prohibit accurate outcomes of the model. As a result, experimental physicists spend their time in labs painstakingly calibrating their setups to minimize all forms of inaccuracy in the modeling. Although accurate calibration is preferable, in many cases it may be possible to instead include these uncertainties into the modeling. Traditionally this would require some theoretical work to find a suitable optimization approach, which may be just as time-intensive as calibration. In this presentation we will see that automatic differentiation based gradient descent can provide a flexible means of computational optimization, since no manual derivation of gradients is required. We show this approach works well for the case of optimization of the tilt angle in extreme ultraviolet EUV reflection ptychography, where it is able to reliably converge, reduce reconstruction artifacts and improve reconstruction fidelity.

Strong coupling between light and molecular matter is currently attracting interest both in chemistry and physics, in the fast-growing field of molecular polaritonics. The large near-field enhancement of the electric field of plasmonic surfaces and their high tunability make arrays of metallic nanoparticles an interesting platform to achieve and control strong coupling. Two dimensional plasmonic arrays with several nanoparticles per unit cell and crystalline symmetries can host topological edge and corner states. Here we explore the coupling of molecular materials to these edge states using a coupled-dipole framework including long-range interactions. We study both the weak and strong coupling regimes and demonstrate that coupling to topological edge states can be employed to enhance highly-directional long-range energy transfer between molecules.

Organic materials have emerged as promising candidates for light-harvesting applications across the infrared to visible spectrum. Their strong excitonic binding energies and large transition dipole moments enable strong light-matter coupling, with some systems reaching the ultrastrong coupling regime. Meanwhile, two-dimensional (2D) materials exhibit high exciton stability and strong electron–hole interactions due to reduced screening. Here, we present a microscopic model describing the interaction of 2D materials and organic molecular aggregates in an optical cavity. We predict the formation of a hybrid Wannier-Mott-Frenkel exciton-polariton with an enhanced Rabi splitting, exceeding that of the pure organic cavity by several tens of meV. As an example, we examine a cavity with 2D tungsten disulfide and a cyanine dye, where this enhancement reaches 5%. The complementary characteristics of Wannier–Mott and Frenkel excitons enable tunable polariton states that merge into a single hybrid state as a function of detuning, supporting dual Rabi splitting mechanisms. This hybrid system offers a versatile platform for exploring quantum optical phenomena in both strong and ultrastrong coupling regimes.

In this work we study the topology of the bands of a plasmonic crystal composed of graphene and of a metallic grating. First, we derive a Kronig–Penney type of equation for the plasmonic bands as function of the Bloch wavevector and discuss the propagation of the surface plasmon polaritons on the polaritonic crystal using a transfer-matrix approach. Second, we reformulate the problem as a tight-binding model that resembles the Su–Schrieffer–Heeger (SSH) Hamiltonian. In possession of the tight-binding equations it is a simple task to determine the topology of the bands. This allows to determine the existense or absence of topological end modes in the system. Similarly to the SSH model, we show that there is a tunable parameter that induces topological phase transitions from trivial to non-trivial. In our case, it is the distance 'd' between the graphene sheet and the metallic grating. We note that d is a parameter that can be easily tuned experimentally simply by controlling the thickness of the spacer between the grating and the graphene sheet. It is then experimentally feasible to engineer devices with the required topological properties. Finally, we suggest a scattering experiment allowing the observation of the topological states.

We investigated a set of films composed by zinc-phtalocyanine (Zn-Pc) dispersed into a poly-methyl methacrylate (PMMA) matrix, to evaluate the radiative cooling performance through the two infrared transparency windows of IR radiation in the atmosphere. ZnPc present strong and accentuated absorption bands in both visible and infrared range and can dissipate energy by radiating in the infrared band. We will firstly describe the process of samples preparation. Afterwards, we will introduce the experimental setup employed for linear optical characterization in the infrared range along with the obtained experimental results. Finally, we will give details about the numerical model that we developed in order to evaluate the radiative cooling effectiveness of the different films.

Radiative cooling is a passive cooling strategy that enables heat dissipation into space through thermal emission in the atmospheric transparency windows (3–5 µm and 8–13 µm), helping to mitigate global warming. In this study, a cost-effective and free standing SBS@TiO₂NPs-MPTMS composite was designed by incorporating 25 nm anatase-phase TiO2NPs, functionalized with 3-(mercaptopropyl)trimethoxysilane (MPTMS), into a styrene-butadiene-styrene (SBS) copolymer matrix. First, several reaction parameters were optimized to achieve well-dispersed TiO₂NPs-MPTMS. Then, composites films containing 1%, 5%, 7% weight percent of TiO₂NPs-MPTMS were prepared and characterized by mid-infrared reflectance spectroscopy (1.6–25 µm). Results showed improved radiative cooling performance with increasing nanoparticle content, evaluated through a quality factor based on emissivity within the atmospheric windows. These findings confirm the potential of SBS-based composites for efficient passive cooling applications.

We report on the lithography-free fabrication of planar cavity-type metasurfaces based on phase-change materials. Multispectral images can be recorded on the presented metasurfaces. This provides a promising platform for optical security and information encryption

The ARTEMIS project aims to develop integrable quantum sources based on metal-organic compounds with transition metal and/or lanthanide ions. These materials exhibit tunable linear emission and nonlinear optical properties, enabling on-demand generation of single photons and entangled photon pairs or triplets. When integrated with plasmonic supernanostructured cavities, these molecular emitters achieve strong optical enhancement. Our group focuses on the quantum characterisation of the light emitted by these sources to explore their potential for new metrology and sensing applications in the quantum regime. Spectroscopic and time-resolved measurements on newly synthesized compounds Tb−N(Bzlm)3 and Eu−N(Bzlm)3 dissovled in DMSO at high concentration reveal narrow emission bands and relatively long decay times.

Fluorohafnate glasses (HfF4–BaF2–LaF3–AlF3–NaF) doped with erbium ions were fabricated by the melt-quenching technique at 870 °C in argon atmosphere, and their spectroscopic properties were studied. The glasses exhibit a low phonon energy (575 cm-1), a broadband mid-infrared emission (stimulated-emission cross-section: 0.51×10-20 cm2 at 2.76 µm), and long luminescence lifetimes of the 4I11/2 and 4I13/2 manifolds making them attractive for 2.8-µm laser sources.

In this study, we investigate the optical scattering properties of self-assembled MoS₂ nanostripes produced by solid precursor film chemical vapor deposition. Employing multiple two-dimensional Finite-Difference Time-Domain (FDTD) simulations with randomly varying parameters, we evaluated far-field scattering behaviors, achieving strong agreement with experimental observations. Our findings emphasize the significant role of intrinsic structural disorder in practical MoS₂-based photonic applications, demonstrating how controlled structural defects substantially impact optical performance.

Hafnium oxide (HfO₂) is of increasing interest in both microelectronics and photonics due to its favorable optical and dielectric properties. In particular, its high refractive index, wide bandgap, and chemical stability render it attractive for optical coatings and metasurfaces down to the ultraviolet spectral range. Atomic layer deposition (ALD) has been commonly employed to produce high-quality HfO₂ films. In this contribution we are reporting on the measured refractive index from a wavelength of 120 nm to 600 nm.

The development of sensors for ultraviolet (UV) radiation with inherent insensitivity to visible light, commonly referred to as 'visible-blind' UV detectors, holds paramount importance across a spectrum of advanced technological applications. Such sensors offer enhanced signal-to-noise ratios by eliminating interference from ambient visible light, crucial for precise detection in fields like flame detection, UV astronomy, and cultural heritage. In this regard, heterojunctions based on wide bandgap semiconductors, such as Ga2O3, present challenges in the production of large-area devices, limiting their implementation in systems requiring extensive detection areas. The need for efficient and scalable 'visible-blind' UV sensors drives the exploration of alternative materials and architectures. In this framework, we show the potentiality of Eu3+-based luminescent materials, usually employed as Luminescent Solar Concentrators, in the detection of UV photons.

We present advances in lithium niobate (LN) photonics for reservoir computing applications. Our dry-etch process achieves 2.5 µm features with sub-10 nm roughness despite lithium fluoride byproduct challenges. While LN platforms exist for time-delay computing, we explore LN as an interconnecting matrix for spatio-temporal reservoir systems. Our approach inscribes optimized phase values through etching, leveraging LN’s nonlinearities to enhance computational performance—demonstrating LN’s advantages.

We studied space-charge waves caused by the competition between holes and electrons in an undoped Bi12TiO20 photorefractive crystal and generated during holographic recording with a 532 nm wavelength laser light and the reflection geometry. A non-linear relation between the velocity of the resonant space-charge waves and light intensity, as well as the photovoltaic effect, is demonstrated. The experimental data is in good agreement with the theoretical model reported here.

Being one of the most important tools in industrial and medical fields, the red-NIR laser has caught much attention in research studies. To enhance the emitting intensity of the red-NIR laser generation from Er3+ ions inserted into a glass network, the effect of Yb3+, Nd3+, and Ce3+ ions on the emitted laser beam was studied. First, a host glass network of 44P2O5-15ZnO-10Pb3O4-15NaF-15MgF2-1Er2O3 (PZPbNMEr³⁺) was proposed as a red-NIR lasing material and was reinforced by 0.5 and 1 mol% of Yb3+, Nd3+, or Ce3+ ions. XRD, density, FTIR, and Raman spectra examined the structural variations resulting from compositional changes, which showed increased glass network tightness. The glass tightness was positively reflected in the thermal stability and elasticity of the considered glasses, reflecting their suitability as lasing media. Optically, all the distinctive absorption bands of the Er3+, Yb3+, Nd3+, and Ce3+ ions appeared in the optical absorption spectra in the 200–2500 nm region. A significant impact of the induced strain or crystal field of the added RE3+ ions was also observed on the optical properties.

This study investigates the surface characteristics of copper plating machined with a single-crystal diamond tool. The surface topographies of the machined samples were evaluated using WLI and AFM. PSD analysis showed that copper plating is smoother than oxygen-free copper at spatial frequencies below 2 × 10⁴ mm⁻¹. Although the PSD of copper plating was the highest above 2 × 10⁴ mm⁻¹ due to its sand-like texture, this did not significantly affect its RMS roughness. Microstructural analysis using EBSD and XRD revealed that the copper-plated surface consists of fine crystalline grains, likely responsible for the observed texture. These results indicate that copper plating can be smoothly machined and is suitable for use in optical components.

On-chip microfluidic devices have gained significant attention for their unique wettability properties. In this study, we developed a microfluidic chip by laser treatment of GPOSS-PDMS polymer film, achieving wettability variations influenced by specific ablation parameters.

Abstract

BaTiO3 is a promising candidate for multi-functional memristive devices with high resistance contrast between ON and OFF states. Doping, as well as native-defect tuning, plays a critical role in the modulation of resistive switching. Herein, a systematic density functional theory (DFT) based studies have been performed to understand the electronic properties of vacancy-induced and doped BaTiO3 systems for optoelectronic applications. DFT calculations have been performed on various possible vacancies and doping on B-sites of BaTiO3 to further confirm the presence of defect states. Partial density of states (PDOS) has been calculated in the case of vacancy-induced BaTiO3, and it is clearly observed that the electronic band gap arises due to the change in the overlapping of O-2p and Ti-3d orbitals, suggesting re-hybridization between these two orbitals. By analyzing the density of states (DOS), charge density, and formation energy calculations reveals the enhancement in the electronic properties after the inclusion of native defects. The present study reveals that a theoretical approach can be used to probe the defect states of systems like perovskites and transition metal oxides.

Aluminum oxide (Al₂O₃), widely known as alumina, is a technologically important material due to its excellent thermal stability, wide bandgap, and optical transparency. In this study, we present a comprehensive theoretical investigation of the structural, electronic, and optical properties of Al₂O₃ using first-principles density functional theory (DFT). The calculations were performed for the stable α-phase of Al₂O₃ (corundum structure), with geometry optimizations confirming experimental lattice parameters. The electronic band structure reveals an indirect bandgap, with a calculated value of approximately ~6.2 eV using the PBE functional, and corrected to ~8.8 eV using the hybrid HSE06 functional to match experimental observations. The density of states indicates that the valence band is predominantly composed of oxygen 2p states, while the conduction band is mainly derived from aluminum 3s and 3p orbitals. Optical property simulations, including the complex dielectric function, absorption coefficient, and refractive index, demonstrate that Al₂O₃ is optically transparent in the visible region and exhibits significant absorption only in the deep UV range. These findings highlight the suitability of Al₂O₃ as a high-k dielectric material and optical coating in next-generation optoelectronic and photonic devices.

Cryogenic single-molecule localization microscopy (cryo-SMLM) enhances photon output and structural preservation but is limited by the lack of fluorophores that blink intrinsically at low temperatures. We demonstrate that nanographene dibenzo[hi,st]ovalene (DBOV) exhibits spontaneous blinking at 91 K, overcoming the need for conventional dyes that depend on liquid buffers. Analysis of intensity time traces yields an average on-state duration of 493 ms and an on-off ratio of 0.043, indicating DBOV’s promise for enabling SMLM at cryogenic temperatures.

Live imaging of 3D cellular cultures, such as organoids, remains a challenging task due to the complexity of acquiring fast volumetric data over the size of the organoid as well as the difficult optical conditions imposed by the matrigel or scaffolds. These support structures, commonly used in organotypic cultures, don't offer properties favourable to imaging as they are typically opaque at visible wavelengths and may poses auto-florescence. This, ultimately, leads to a degradation of image quality and loss of signal-to-noise ratio.

In this work, we present a novel oblique plane microscope (OPM) aimed at tackling these challenges. In our setup, we bring together adaptive optics techniques, multi-directional illumination, and structured illumination in order to increase the penetration depth of both the detection and excitation beams. Additionally, we implement a recently developed remote refocussing scheme that removes the necessity of secondary and tertiary objectives - commonly used in OPM setups - reducing the cost and technical complexity of the microscope.

Accurate and continuous respiratory and heart rate monitoring is essential during medical procedures to ensure patient safety. This work explores the feasibility of using LPGs for monitoring in clinical environments where immunity to electromagnetic interference is crucial. Preliminary analysis and results suggest the validity of the proposal. Future research will focus on experimental validation and signal processing techniques to enhance performance.

Hexagonal boron nitride (hBN) is emerging as a promising platform for single-molecule biophysics studies due to its favourable combination of structural, chemical and optical properties. It is an atomically smooth and inert 2D material that is optically transparent, and which enables studies of biomolecule dynamics in 2D confinements at the single-molecule level [1]. In this work we show that ATTO647N-labelled ssDNA structures immobilized on a coverslip underneath hBN flakes can be imaged with TIRF microscopy with single-molecule resolution and retain their emissive properties. We compare the photophysics of the fluorophores in buffer, in air and under hBN coverage, and find that the hBN coverage decreases the photo switching rate compared to Atto647N exposed to ambient conditions. The ON-time and intensity before bleaching of the fluorophores shows a decrease compared to those in buffer and varies as a function of the hBN thickness. We ascribe this to the presence of lattice defects in the hBN, which can exchange energy with the fluorophores. The arrangement of the dyes can be accurately imaged, showing promise of this platform as a single-molecule FRET platform for surface-based biosensing.

[1] Diffusion of DNA on Atomically Flat 2D Material Surfaces, Dong Hoon Shin, et.al., bioRxiv 2023.11.01.565159; https://doi.org/10.1101/2023.11.01.565159

Femtosecond laser micromachining (FLM) has emerged as a power-

ful technique for the precise fabrication of optical components, enabling high-

resolution structuring in transparent materials such as fused silica and borosil-

icate glass. The nonlinear absorption mechanisms involved allow for localized

modifications at the microscale with minimal thermal effects. In this work, we

demonstrate the application of FLM for the fabrication of integrated optical

beam splitters and microlenses. By carefully controlling laser parameters and

subsequent post-processing steps, we achieve structures with high optical qual-

ity and functional performance. The results demonstrate the potential of fem-

tosecond laser technology in integrating complex optical components, opening

new possibilities for the development of lab-on-chip systems.

Single-molecule detection is crucial for probing molecular interactions, but weak fluorescence signals and the risk of photodamage from high laser intensities limit current approaches. Conventional enhancement methods often require dried samples or introduce compatibility issues, making them unsuitable for dynamic, in-solution measurements. We present a hybrid platform that combines photonic crystals (PhCs) with hexagonal boron nitride (hBN), which provides an effective surface for constraining single-stranded DNA (ssDNA), allowing vertical immobilization while preserving lateral mobility. Simulations show a 218-fold increase in electric field intensity at the hBN surface, enabling significantly brighter fluorescence without increasing laser power. This localized enhancement reduces the risk of photodamage by minimizing overall light exposure. The platform maintains label compatibility and molecular mobility, offering a scalable and biocompatible solution for real-time single-molecule tracking and high-sensitivity biosensing.

We describe the rules to enhanced the Brillouin interaction in silica nanofiber.

We report a focused optical vortex array (FOVA) generator prepared by printing a Dammann spiral zone plate on the composite fiber facet using femtosecond laser two-photon polymerization. The generation of FOVA is verified by simulation and experiment. The all fiber generator of FOVA exhibits high flexibility and compactness, making it a suitable candidate for applications in fields such as optical manipulation and optical communications.

Polarization-maintaining properties for a nested tube negative curvature hollow-core fiber are numerically investigated when the whole fiber cross-section is subjected to physical deformation leading to elliptical fiber forms. The results indicate that ellipticity provides a useful fine-tuning mechanism for polarization maintaining operation of fiber.