Conference Agenda

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.

Transparent ceramics of Holmium-doped yttria (Ho:Y2O3) were fabricated by Hot Isostatic Pressing at 1720 °C / 190 MPa in argon, and the effect of YF3 addition on their microstructure, optical, vibronic and infrared emission properties was studied. The fluorine addition improves the ceramic transparency, accelerates the grain growth and enhances the luminescence lifetimes of Ho3+ states responsible for emissions at 2 µm and 3 µm.

In the context of the quest of organic laser diode, we propose a method to compare organic gain semiconductors in terms of laser threshold before integrating them into laser cavity. This method is based on three types of measurements for each material: 1-measurements of absorption and photoluminescence spectra to evaluate the re-absorption, 2-measurement of fluorescence lifetimes linking the potential laser gain to the current in the diode and 3-measurement of the gain of the amplified spontaneous emission. This approach is validated by laser threshold measurements carried out under optical pumping for two organic compounds DCM and DCJTB deposited on laser cavities

We report on a comprehensive spectroscopic study of singly Dy3+ doped and Er3+,Dy3+ codoped calcium fluoride (CaF2) crystals for midinfrared laser applications. The f-f transition probabilities of Dy3+ were determined by the Judd-Ofelt theory. The stimulated-emission cross-section reaches 0.25×10-20 cm2 at 2.93 µm corresponding to an emission bandwidth of 350 nm. The Er3+ → Dy3+ energy transfer efficiency in codoped crystals is quantified. The 4.4-µm Dy3+ emission is observed for the first time from fluorite crystals.

Surface-doping of lithium niobate wafers with rare earth or optically damage-resistant ions by physical vapour deposition and high-temperature in-diffusion is a cost-efficient and flexible method for the fabrication of thin-film LN or LNOI with dopants which are not common in crystal growth. LNOI doped with different concentrations of Er, Yb, Tm, Pr, Zn and Zr has been fabricated. As an example, the fluorescence spectra of Er:Yb:LNOI samples were recorded, and a high small-signal gain of 35 dB/cm was measured in ridge waveguides.

The objective of this work is to design a secondary luminescent concentrator (LC) -optically pumped by a YAG:Ce primary luminescent concentrator- then emitting photons between 1.0 and 1.5 µm in the SWIR. The main properties should be a good overlap of the absorption spectrum with the YAG:Ce emission, a high quantum efficiency value for the Ni2+ emission, and a good optical quality of the crystal to limit losses. Ni2+ doped lasers crystal such as LaMgAl11O19:Ni and YAlO3:Ni or LiGa5O8:Ni glass-ceramics can be proposed and are investigated within this work.

Lanthanum oxysulfide powders doped with Erbium ions were fabricated by the combustion method followed by sulfurization at 1000 °C under H2S + N2 atmosphere. X-ray diffraction confirms their single-phase nature (sp. gr. P-3m1). Raman spectroscopy reveals a maximum phonon energy of 389 cm-1. The effect of Er3+ doping level (0.5 – 7 mol%) on the visible and mid-infrared emission properties of Er:La2O2S was studied.

Studies on individual nano-emitters offer fundamental insights into their spectral properties and emission characteristics. The signal intensity of e.g. dye molecules in fluorescence assays can be improved by coupling them to plasmonic nano-antennas. The properties of the hybrid system crucially depend on the specific position of the emitter relative to the antenna, which however cannot be resolved by conventional microscopy. An approach is demonstrated that uses nanocones as the antennas and point-spread function deformations for localization determination. Intensity time traces are investigated to study binding statistics, location-dependent enhancement factors and fluorescence reshaping.

The objective of this work is to study the effects of plasmonic

nanoparticle arrays on the emission of organic semiconductors used for

OLEDs. As a first step, we report the investigation of the response of Agbased arrays in various configurations in terms of geometry and structure.

Metamaterials are artificially structured media offering multiple applications. Among them, epsilon-near-zero (ENZ) metamaterials are a platform for enhanced nonlinear optical phenomena. Multilayer hyperbolic metamaterials (MHMs) belong to the latter class and are tailorable structures for the study of the optical Kerr effect (OKE). In this work, different ENZ Au/SiN MHMs are crafted, their OKE parameters are spectrally characterized, and the nonlinear response temporal dynamics is studied.

Amorphous silicon carbide offers unique properties for the optimiza-

tion of microstructured optical elements. We present a study on the technologi-

cal processing, the resulting material properties as well as potential applications.

Persistent phosphors, especially in nanophosphor form, are valued for their long-lasting afterglow and are promising for applications like anticounterfeiting, data storage, and imaging displays. However, their use is limited by challenges in tuning their properties and low energy storage capacity. This work introduces a novel transversal strategy to enhance persistent luminescence in nanophosphor thin films by modifying their optical environment without changing their composition. Using the sol-gel method, we fabricated layered garnet films with time-dependent chromaticity and developed transparent ZnGa₂O₄:Cr³⁺ films embedded with TiO₂-based scattering centers. This design led to a 3.5-fold increase in afterglow intensity and faster charging, thanks to enhanced light absorption and improved outcoupling. This approach demonstrates a powerful and versatile way to optimize persistent nanophosphors, opening new opportunities for creating advanced coatings with dynamic luminescent properties, particularly for high-performance anticounterfeiting applications.

The benefits in terms of cost efficiency and versatility achieved through the development of flexible and stretchable electronics and optoelectronics have greatly fueled the exploration of flexible photonic technologies. Introducing mechanical flexibility to photonic structures enables novel functionalities, further broadening their range of applications. Alongside advancements in flexible photonics based on organic platforms, an emerging approach is gaining attention, emphasizing the use of inorganic, all-glass ultra-thin structures. For oxide-based materials, their intrinsic properties, such as transparency, high thermal resistance, and chemical stability, can be harnessed within appropriate systems.

We present flexible SiO2/HfO2 one-dimensional photonic crystals, fabricated via radio frequency sputtering. These systems exhibit a pronounced dependence of their optical properties on the angle of light incidence, particularly demonstrating a blue-shift of the stopband and a narrowing of the reflectance window. However, the most remarkable finding lies in the experimental evidence showing that even after breakage, with visible cracks forming in the flexible glass, the multilayer structures largely retain their integrity. This positions them as promising candidates for flexible photonic applications due to their robust optical, thermal, and mechanical stability.

This research is supported by the projects: CANVAS, LEMAQUME-QuantERA, Project PNRR NFFA-DI IR0000015, PRIN 2022 PNRR P2022YM8J3 - NANOSEES, HORIZON-TMA-MSCA-DN Met2Adapt.

This work focuses on the optimization of a compact square prismatic single stage solar concentrator to be realized either with BK7 glass or Silopren plastic. Zemax software is used to simulate and optimize the optical surfaces. The concentrator consists of a spherical surface atop a parallelepiped, placed above an inverted truncated pyramid. The simulated optical efficiency, without any antireflective coating, ranges between 89% and 96%, with a concentration factor of 400 suns, and an acceptance angle ranging between 0.8° and 1.0°. The collection surface is 5x5 mm2, and the total concentrator height is 10 mm. The optics has been designed to operate in micro-concentrating photovoltaic modules.

This study investigates thiophene oligomers as fluorophores incorporated within poly(methyl methacrylate) (PMMA) films, fabricated using slot die coating. This versatile technique ensures high optical quality and excellent reproducibility of the deposited films, provided reliable coating parameters are established. Optimized coating conditions yielded highly fluorescent films with a thickness of 30 µm, which were then employed to develop Luminescent Solar Concentrators (LSCs). Electrical characterization, conducted in accordance with standard procedures, revealed that oligomers exhibiting larger Stokes shifts demonstrated superior device performance due to reduced re-absorption losses. These findings underscore the potential of thiophene oligomers for efficient LSC applications.

Ridge low loss (0.16±0.02 dB/cm) waveguides were fabricated in Pr,Gd:LiYF4 epitaxial layers by precision diamond-saw dicing. The red waveguide laser generated 504 mW at 639.7 nm with a slope efficiency of 57.8%, a linear polarization and a laser threshold of 34 mW. Laser operation in the orange and deep red was also demonstrated.

J-aggregates thin films of cyanine dyes are very attractive organic nanomaterials formed by highly ordered assembly of supramolecular organic structures. These films show unique spectroscopic properties, making them promising candidates for integration into advanced electronic and photonic devices. Their spectra show very narrow resonances, resulting in spectral regions with high refractive index, comparable to semiconductors, and negative permittivity, similar to metals. This study focuses on the characterization of the optical properties of cyanine J-aggregates thin films, including refractive index and permittivity, in a wide spectral range from visible to near infrared wavelengths. Our findings highlight the potential of these structures for the development of sustainable photonic devices.

This study presents a technique for measuring the thermal conductivity of materials based on the strong reflectance change caused by the insulator-to-metal transition in VO₂ thin films. Unlike conventional pump-probe and frequency-domain thermoreflectance techniques, this approach is based on steady-state optical microscopy. The presented technique involves imaging the metallic domain induced by a continuous-wave laser beam illumination on the VO₂ surface as a function of laser intensity. By fitting the radius-intensity relationship with a theoretical model developed for this purpose, the thermal conductivities of three materials (silica glass, sapphire, and silicon) are accurately determined, yielding values in good agreement with the tabulated data.

Oligonucleotide optical switches are suitable molecules capable of turning on or modifying their light emission on molecular interaction with well-defined molecular targets. Among all the possible switches, molecular beacons (MBs) represent a powered tool for the detection of RNAs, such as micro-RNA (miRNA), long noncoding RNA (lncRNA), and messenger RNA (mRNA), which play an important role as indicators of the progress of different pathologies in the human body, from the chronic ones to cancer. In this work, the decennial activity carried on by the authors on the design of MBs specific for different targets, on their use as biorecognition elements for different optical setups (i.e. fluorescence o SERS based platforms), on their application for drug delivery in cell, etc., has been reported.

Nanostructures on bodies of biological inhabitants in severe environments can exhibit excellent thermoregulation, which provide inspirations for artificial radiative cooling materials. However, achieving both large-scale manufacturing and flexible form-compatibility to various applications needs remains as a formidable challenge. Here a biomimetic strategy is adopted to design a thermal photonic composite for high-efficiency daytime radiative cooling. Cicadae, thermophilic insects that have been startlingly reported to have higher population densities as the urban heat island (UHI) intensity is growing, have attracted little attention for their thermoregulation. In this work, the optimized thermoregulatory ability of golden cicada’s hair is first studied. Then, a microimprint combined with phase separation method is developed for fabricating a biomimetic photonic material made of porous polymer–ceramic composite profiled in microhumps. The composite demonstrates high solar reflectance (97.6%) and infrared emissivity (95.5%) in atmospheric window, which results in a cooling power of 78 W m-2 and a maximum subambient temperature drop of 6.6 °C at noon. Moreover, the technique facilitates multiform manufacturing of the composites beyond films, as demonstrated by additive printing into general 3D structures. This work offers biomimetic approach for developing high-performance thermal regulation materials and devices.

We utilize the de novo protein design to create bioinspired four-helix bundle maquettes capable of supporting artificial chromophore arrangements. These robust, water-soluble scaffolds were functionalized with Zn-pheophorbide a (ZnPa) and Rhodamine 101 (R101). The resulting complexes exhibited broad visible absorption, and modulated ZnPa emission due to energy transfer from R101 to ZnPa. Spectroscopic analyses supported by Molecular Dynamics simulations revealed the occurrence of excitonic coupling between ZnPa and R101. Our work demonstrates the potential of rationally engineered proteins as a sustainable platform for developing light-harvesting systems.

Photonic structures integrated with responsive photoresists have garnered significant attention, particularly following the advancements in two photon lithography. The pH responsive photonic array presented exhibits robust structural stability and generates progressively changing structural colours in transmission across various pH buffered solutions, highlighting their strong potential for biosensing applications.

Lanthanide β-diketone complexes, renowned for their luminescence, are pivotal in designing multifunctional advanced materials for diverse applications, including lasers, energy harvesting, and sensing. This work utilizes supramolecular Eu³⁺ bis-β-diketones as dopants in poly-methyl-methacrylate (PMMA) to fabricate highly transparent, luminescent polymeric slates. These systems, exhibiting exceptional molar brightness, are explored as luminescent solar concentrators (LSCs) for building-integrated photovoltaics (BIPVs). PMMA/Eu³⁺ slates, synthesized via cast polymerization, demonstrate high transparency (AVT=92%, CRI>98) and effective UV absorption (300-400 nm), crucial for both aesthetic integration and UV protection. Coupling these slates with Si solar cells yielded LSC-PV devices, characterized according to standard guidelines. Notably, these devices achieve comparable performance to literature analogues, despite a 10-100 fold reduction in Eu³⁺ content, demonstrating efficient material utilization.