Conference Agenda

Analysis of defects in optical materials is crucial for their applicability in cutting-edge optical components. Since calcium fluoride (CaF2) is highly regarded for optical applications, understanding the nature of defects within CaF2 is particularly significant. These defects have been conventionally identified through absorption and photoluminescence (PL) emission studies. In this work, we investigate the defects by measuring laser-induced fluorescence (LIF) spectra over a long irradiation. By decomposing the PL spectrum into multiple Gaussian PL bands, we identify the defects within the CaF2 material. The measurement of irradiation-induced PL can be rationalized by the stabilization of F-centers via the formation of M-centers. PL mapping has been also studied to study the potential link between the surface oxygen contamination of CaF2 samples and polishing techniques.

Metal-Organic Frameworks (MOFs) have emerged as promising candidates for detecting metal ions owing to their large surface area, customizable porosity, and diverse functionalities. In recent years, there has been a surge in research focused on MOFs with luminescent properties. These frameworks are constructed through coordinated bonding between metal ions and multi-dentate ligands, resulting in inherent fluorescent structures. Their luminescent behavior is influenced by factors like structural composition, surface morphology, pore volume, and interactions with target analytes, particularly metal ions. This study investigates the impact of Fe3+ cation exchange on the structural, thermal, and photoluminescent (PL) properties of MIL-53(Al) MOF samples. Incorporating Fe3+ ions induces structural distortions, altering coordination environments and leading to amorphization. Enhanced metal-ligand bonds boost thermal stability, delaying decomposition processes. Raman peak changes reflect ionic and charge disparities, disorder from cation exchange, and electronic effects. PL emission spectra variations reveal MOF framework influence on emission characteristics, with Fe3+ exchange quenching PL intensity and shortening lifetimes due to structural distortions and stronger linker binding, favoring non-radiative decay. These findings underscore the complexity of MOF interactions, crucial for applications like catalysis, gas storage, and luminescent devices. Cation exchange emerges as a promising strategy for tailoring MOF properties to specific needs.

3D-hollow microstructures with few tens of micrometer in diameter and up to 330 µm in length with an optical-quality surface roughness (Ra ≤ 1 nm) have been fabricated in the volume of lithium niobate by selective etching of fs-laser written structures and post-etching annealing. The fs-laser writing parameters and the annealing process have been refined to reduce the average surface roughness and the shape change. Systematically investigating the annealing process, a functional description of the temporal evolution of the surface roughness was found completing the data set of processing parameters for selective etching of fs-laser written structures, allowing to control the fabrication process of the hollow microstructures concerning both shape and surface roughness precisely. Thus, our results represent another milestone within the research towards monolithic micro-(opto)fluidic applications inside the multifunctional crystal lithium niobate.

Planar X-cut lithium niobate (X-LiNbO3) optical waveguides were prepared by proton exchange in benzoic acid. We carried out Raman spectroscopy of proton exchange (PE) and annealing proton exchange (APE) in the cross-section of the substrate. The E(TO1) mode after annealing indicates compositional disorder near the surface, while it is not visible by Raman before annealing. In order to isolate the PE film, undercut has been performed by focused ion beam (FIB). The isolated film presents no more ETO1 but spectra characteristic of LiNb3O8. Ab-initio calculations confirm stable proton exchange layers of HNbO3. The focused ion beam seems to have activated the cubic phase of HNbO3 to monoclinic LiNb3O8. Rhombohedra LiNbO3, cubic HNbO3 and monoclinic LiNb3O8 transform coherently.

Vanadium dioxide has attracted much interest due to the drastic modification of the electrical and optical properties it undergoes following the transition from the semiconductor to the metallic state, which takes place at a critical temperature of about 68°C. Many advanced fabrication methodologies have been proposed to improve the performance of VO2 thin films for phase-change applications in optical devices. Here, a purely optical approach is proposed, combining Phase-Transition by Continuous Wave Optical Excitation and Polarized Raman Mapping to acquire both morphological and thermal behaviour information of pulsed laser deposited polycrystalline VO2 thin films. The combination of the two techniques allows to reconstruct a complete picture of the properties of the samples in a fast and effective manner, for comparison and optimization purposes, but also to unveil an interesting stepped structure of the hysteresis cycles.

There has been an unprecedented increase in the growth of photonic components over the last 25 years based on different photonic materials; each having structural/functional limitation in integrated devices.

The challenge is that the semiconductors are grown inside MBE chambers, whereas the polymeric waveguides are fabricated by spin-coating. By comparison, glass and crystal-based materials are processed via sputtering and sol-gel techniques. None of these materials processing techniques, therefore, are compatible for a single-step device fabrication, due to the incompatibilities of chemical and physical properties of individual materials. A solution for overcoming the materials limitation is to develop a multi-materials deposition chamber which allows sequential/heterostructure growth on a substrate, without compromising the structural, spectroscopic, and device performances. The rare-earth-ion doped glass- and crystal-based devices are pumped with semiconductor lasers, suggesting that the glass-semiconductor devices might perform better when structurally integrated which may also help in reducing the pump-power for achieving efficient population inversion.

We explain the applications of PLD for controlling the structure of thin-films grown on inorganic and metallic substrates for photonic device and photo-active coatings for biological applications, respectively. Examples of materials deposited on dissimilar substrates are discussed with applications such as photonic devices and photo-bioactive surfaces for sensing.