Conference Agenda

Requirements for high-performance optics are continously increasing. As a result, substrate geometries and coatings grow more and more complex, posing challenges with respect to precision optics manufacturing, deposition technology and metrology as well as cost effectiveness and lead times. Navigating these constraints can be demanding, especially for beginners in the field. Possible issues, trade-offs and lessons learned will be presented here.

This tutorial will concern at least the following TOMs:

TOM3: Optical System Design, Tolerancing and Manufacturing

TOM7: Ultrafast Phenomena

TOM10: Applications of Optics and Photonics

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Thorlabs manufactures an extensive family of mid-IR fluoride fiber using proprietary techniques that provide world-class purity, precision, and strength. These techniques give us excellent control over the fibers' optical and mechanical properties, allowing a wide range of configurations to be drawn. In this tutorial we will highlight these techniques, the history of fluoride fiber R&D, and the state of fluoride fiber technology today and in the future.

This tutorial will concern at least the following TOMs:

TOM3: Optical System Design, Tolerancing and Manufacturing

TOM 6: Optical Materials

TOM 10: Applications of Optics and Photonics

Optical frequency comb based on microresonator (microcomb) is an integrated coherent light source

thanks to its high integrity, low power consumption, and low phase noise. Especially, octave spanning

microcombs via dispersion engineering can realize a chip-scale 2f-3f or f-2f self-referencing scheme and

has the potential to promise a high-precision frequency standard. In practice, the stability of the soliton

comb source is the basis of subsequent signal processing. However, achieving a long-term stable soliton

comb can be challenging due to thermal effects or center frequency jitter induced by the pump. This often

requires a complex feedback system, which hinders the minimization of the device.

Domain reversal engineering stands out as an essential procedure for realizing effective nonlinear conversion on periodically poled lithium niobate on insulator (PPLNOI), laying a promising foundation for nonlinear photonic integrated circuits (PICs). However, the domain reversal for thin-film lithium niobate has been confined to the chip scale, hindering its use in extensive nonlinear photonic systems. Here, we present a wafer-scale periodic poling platform on a 4-inch LNOI wafer, covering reversal lengths from 0.5 to 10.17mm and periods ranging from 4.38 to 5.51 μm with high fidelity. The efficient poling is enabled by a single operation over ~1 cm^2 area, using strategically grouped electrode pads and adjustable comb line widths. We achieved a 100% success rate and a 98% high-quality rate on average, showcasing high throughput, stability and scalability, making it more economically viable than chiplet-level poling. Our research holds immense potential to significantly enhance ultra-high performance for applications in optical communications, photonic neural networks, and quantum photonics.

We reported structured NIR dual-optical parametric oscillators (OPOs) and tri-wavelengths yellow-orange beams from a monolithic periodically poled lithium tantalate. The structured dual-OPOs comprise of dual-signal wavelength at 980 and 964 nm, which are residing on the opposite sides of TEM10 cavity mode. By introducing additional up-conversion processes, a structured tri-wavelength yellow-orange TEM20 cavity mode can be observed. We consider a numerical model by including a Laplacian operator in the transverse plane to simulate the distribution of dual OPO. Our calculation indicates that the structured mode was attributed to the transversally inhomogeneous nonlinear optical gain.

Optical damage resistant ridge waveguides for blue and near UV wavelengths have been fabricated using high-temperature Zr and Zn diffusion doping and vapor transport equilibration (VTE) of congruent LiTaO3 crystals. For both dopants high optical damage thresholds >10 MW/cm2 for 532 nm light were demonstrated at room temperature, which can be increased by a factor ~3 when heating the samples to ~150°C. Ridge waveguides with low optical losses of ~0.4 dB/cm were fabricated using diamond-blade dicing. First-order periodic poling with grating periods of ~3 um can be used for efficient nonlinear frequency conversion for both SHG (800 nm pump) or SPDC (400 nm pump) processes.

The aim of the PhD project is to develop a new trend in modulation system for Exail company: thin film (<1 µm) lithium niobate (LN) electro-optic modulator. It exhibits better performance in term of bandwidth, power consumption and footprint than legacy ones [1-3]. This PhD is a cooperation between Exail photonics which is world-renowned for the performances of their electro-optic modulators and FEMTO-ST institute which can offer the possibility to grow stoichiometric LN thin film by means of direct liquid injection metalorganic chemical vapor deposition (DLI-MOCVD). This cooperation opens the possibility to obtain industrialization of optical device based on CVD LN stoichiometric layers which allow to have enhanced performances such as higher electro-optic coefficient than that of congruent compositions of commercial single crystals. Thus, all steps from MOCVD layer deposition to modulator realization can be done here in Besançon

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.

In modern optical engineering, tunable optical devices play a crucial role in dynamically controlling key optical parameters, enhancing functionality and adaptability. Various mechanisms, such as electrical gating, optical pumping, mechanical actuation, phase transitions, magneto-optical effects, and nanostructured nonlinearities, enable real-time adjustments at the nanoscale level. This facilitates enhanced functionalities like tunable focusing, beam steering, frequency tuning, and polarization control, along with improved imaging and aberration correction in optical systems. A novel approach involves selectively controlling spatial regions for optical tuning, achieved through organic mixed ion-electron conductors like PEDOT:PSS. This conductive polymer offers flexibility, thermal stability, and easy fabrication, with remarkable electrostatic tunability by injecting mobile ionic species from an adjacent electrolyte. By adjusting the bias between electrodes connected to the polymer, full control over material properties can be achieved, enabling the realization of a tunable broadband gradient index material without complex fabrication processes.

Nanosphere lithography is a cost- and time-efficient tool for the fabrication of various nanostructured materials. Multiple steps of metal layer deposition at different oblique angles were shown to produce complex asymmetric and chiral shapes. Here, we investigate samples in which polystyrene nanospheres are covered by Ag or combination of Ag and Au at a single step (under 45°). In this way, we obtain metasurfaces with asymmetric shells, with a nanohole array formed due to the shadowing effect. We investigate chiro-optical properties of four samples by exciting them in the 700-1000 nm range, at angles of incidence from -45° to +45°; we report on dissymmetry in the total extinction between left and right circularly polarized excitation gext, which follows the rules of extrinsic chirality. We then resolve the transmission of Ag metasurface in terms of hyperspectral Stokes parameters, and we connect the S3 parameter with gext. Finally, we characterize nanohole arrays obtained from the same samples when the nanospheres are removed; we further perform electromagnetic simulations to gain insight into the “egg” shaped nanohole.

All-dielectric, sub-micrometric particles obtained through solid state dewetting support Mie resonances together with a high-quality monocrystalline composition. Although the scattering properties of these systems have been qualitatively investigated, a precise study on the impact given by the effective com-plex morphology of a dewetted nanoparticle to the Mie scattering properties is still missing. Here, by us-ing morphological characterization, phase field modelling and light scattering simulation, we provide a realistic modelling of the single scatterer optical properties. Moreover, by means of the Dark-field Scan-ning Optical Microscopy characterizations and numerical simulations of light scattering, we show how the presence of a pedestal enriched with silicon placed under the SiGe-nanoparticle results in a sharp peak at high energy in the total scattering cross-section. Exploiting a tilted illumination to redirect scat-tered light, we can discriminate the spatial localization of the pedestal-induced resonance, extending the practical implementations of dewetted Mie resonators in the field of light scattering directionality and sensing applications.

Multilayered metal-dielectric nanostructures display both strong plasmonic behavior and hyperbolic optical dispersion. The latter is responsible for the appearance of two separated radiative and non-radiative channels in the extinction spectrum of these structures. This unique property can open plenty of opportunities towards the development of multifunctional systems that simultaneously can behave as optimal scatterers and absorbers at different wavelengths, an important feature to achieve multiscale control light-matter interactions in different spectral regions for different types of applications, such as optical computing or detection of thermal radiation. Nevertheless, the temperature dependence of the optical properties of these multilayered systems has never been investigated. In this work, we study how radiative and non-radiative processes in hyperbolic meta-antennas can probe temperature changes of the surrounding medium. We show that, while radiative processes are essentially not affected by a change in the external temperature, the non-radiative ones are strongly affected by a temperature variation. By combining experiments and temperature dependent effective medium theory, we find that this behavior is connected to enhanced damping effects due to electron-phonon scattering. Our study shows that our system can be used as very sensitive thermometers via linear absorption spectroscopy.

The influence of rapid thermal annealing (RTA) onto chalcogenide Ge-Sb-Se thin films is reported, focusing on changes in optical properties. These materials possess broad mid-infrared transparency covering the most critical absorption bands for (bio)chemical sensing and high third-order optical nonlinearities for potential applications in nonlinear photonics. The parameters of the RTA process within this study include the annealing temperature, heating rate, and the two sample processing methods – one by placing the sample inside the graphite susceptor and the other by simply laying the sample onto the silicon wafer. Selenide thin films were found to undergo a shift of the absorption edge upon the RTA, resulting in an optical bandgap energy increase (bleaching effect) and a notable refractive index decrease. As a result of structural relaxation, such changes show a great potential of RTA in fine-tuning of optical performance of chalcogenide thin films and planar chalcogenide waveguides. The authors acknowledge the IBAIA (101092723) Horizon Europe project, the ANR AQUAE (ANR-21-CE04-0011-04) project of the French National Research Agency (ANR), and project No. 22-05179S of the Czech Science Foundation (GAČR) for financial support.

Random laser (RL) based on Rhodamine 6G (Rh6G) doped silica xerogel, fabricated by a conventional sol-gel (SG) synthesis, was observed around 590 nm, in a large band typical from dye RLs. Different from other previous works, where the xerogel is just impregnated or infiltrated of dye solution, here the Rh6G was added during the SG synthesis. The obtained material was grinded using a mortar and a pestle, and the resulting powder was carefully packed in a sample holder and pumped at 532 nm using a 6 ns pulsed laser. We used spectral and images measurements to perform statistical analysis and describe experimentally the Parisi replica breaking symmetry (RSB) phenomenon in a complex system. These results show that RSB obtained from images is a promising method for RL characterization. Indeed, by calculating the RSB maps, we demonstrate that the RL emission is not a homogenous process, depending on the scattering and gain properties of different regions.

In the last few years, quantized nanolaminates (QNL) have become increasingly popular as a metamaterial in the development for optical coatings. Experiments were often performed using IBS or ALD coating techniques, which yield excellent accuracy but are very time consuming to coat. By using a magnetron sputter system with rotating substrate table, we are able to produce these layers at very high deposition rates and to use these nanolaminates as standalone high index material in optical designs. Due to the properties of QNL to increase the band energy and thus shift the absorption edge into lower wavelength ranges, it is possible to create designs in the UV range that would not be possible with simple Ta2O5-SiO2 material combination in regular designs. In this work we show a selection of different designs such as anti-reflective coatings, mirrors and short pass filters at wavelengths from 266-355nm which covers an important range in laser applications.

Two-dimensional transition metal dichalcogenides (2D TMDCs) have gained significant attention from the scientific community due to their exceptional properties, making them extremely attractive for optoelectronic and photonic applications. However, many exfoliation or synthesis techniques yield 2D crystals with limited crystalline quality and/or small lateral size. Here, we report a facile Au-assisted exfoliation method, yielding high-quality, large-area monolayers with lateral sizes of hundreds of micrometers. A self-assembled monolayer of (3-aminopropyl)triethoxysilane (APTES) is employed to improve the adhesion between the 2D material and the target substrate, dramatically improving the yield and reliability of the exfoliation process. The monolayer nature of the final sample is then assessed by means of Imaging Spectroscopic Ellipsometry (iSE), which enables a quick and reliable thickness mapping over millimeter-sized areas

Strong coupling with light has emerged as a powerful tool for modifying the properties of optical materials. Typical systems are based on a fluorescent layer embedded in a single optical cavity, whereby the excitonic emission is converted into a polarized, energy-tunable and dispersive polariton emission. There, excitons and photons coexist in the same volume and therefore any change in the emission properties of the excitonic material comes at the expense of simultaneously modifying the photonic environment where excitons reside, i.e., layer thickness and refractive index. Here, we demonstrate remote control over the intensity and total decay rate of the fluorescent layer by adding an extra purely photonic cavity strongly coupled to the first one. By modifying the resonant condition of the extra cavity, we reduce the total decay rate and suppress the fluorescence intensity of the fluorescent layer without explicitly affecting the first cavity. Such modification of the optical properties of the layer is the consequence of a resonant configuration that spatially segregates photons and excitons into different cavities.

Thanks to their excellent photoluminescence quantum yields, their facile and low-cost production, and their processing versatility, CsPbBr3 perovskite nanocrystals (NCs) stand out as excellent candidates to implement light-emitting devices. Elucidating their stimulated emission mechanisms is fundamental to achieve much more efficient and versatile perovskite lasers. In particular, two questions remain open: why the Amplified Spontaneous Emission (ASE) band is significantly shifted from the fluorescence one, and why the former seems to suddenly emerge from, and coexist with, the latter. These characteristic features have led to a debate, which is not settled yet, on which is the mechanism behind the ASE band shift. In this communication, we try to settle this debate and address these questions through experimental ASE measurements combined with numerical simulations. We show that the ASE behaviour in CsPbBr3 NCs thin films stems from a combination of reabsorption, excited state absorption, excitation of differently polarized waveguide modes, and the coexistence of short- and long-lived localized single excitons. The results in this work help understanding the stimulated emission mechanisms in perovskites and provide insightful information on research avenues to increase the efficiency of the light-emitting devices based on these materials.

Year by year, the importance of plastic nanostructures in photonics is increasing. Indeed, polymers represent an interesting alternative to more traditional metal oxides, being easily processable and allowing for light, free-standing and flexible structures. In the field of energy efficiency and sustainability, we bring in two positive examples of the use of plastic photonic crystals: sensing and thermal shielding. In sensing they allow for easy detection of analytes, such as the byproducts of food degradation; a colour change identifies the spoilage, with possible application of these plastic sensors in smart packaging applications. On the other hand, they can be of interest for thermal shielding applications. Indeed, they can be engineered as thin, transparent films able to reduce indoor heating by sunlight and in turn the energy consumption related to the use of air conditioning.

A Tm:LiYF4 laser operating on the 3H4 → 3H5 transition is integrated into a high-power diode-pumped Nd:ASL laser for intracavity upconversion pumping at 1.05 µm. This architecture leads to a record-high output power at 2.3 µm ever extracted from any upconversion pumped Thulium laser. The continuous-wave Tm-laser yields 1.81 W at 2.3 μm at 32 W of laser-diode pump power at 0.8 µm, rivalling direct diode pumping. The intracavity pumping mitigates weak absorption inherent to the upconversion pumping scheme and disperses the deposited heat over two laser crystals. This laser design minimizes heating of the Tm-crystal and enhances the tolerance to Tm3+ excited-state absorption, being promising for high-power 2.3-µm solid-state lasers based on thulium ions.

We report on an original chaotic dynamic behaviour of a passively Q-switched 2.3-µm Thulium laser operating on the 3H4 → 3H5 transition. The experiment employs a Tm:LiYF4 laser crystal within various laser cavity configurations, involving optional additional cascade laser operation on the 3F4 → 3H6 transition at 1.9 µm. The saturable absorber employed is Cr2+:ZnSe, which is exclusively saturated by the 2.3 µm laser emission. A precise analysis of the Q-switching dynamics shows a pronounced inclination of the cascade laser scheme towards chaotic operation. To investigate the origins of chaos, we originally monitor the metastable 3F4 level population using cascade laser operation at 1.9 µm, which proves to be a crucial underlying parameter for explaining the observed instabilities. This analysis allows for explaining the specific dynamics of the Q-switched 2.3 µm Tm-laser intrinsically linked to Tm3+-doped materials. A very atypical route to chaos for a Q-switched laser is demonstrated involving type I intermittencies. The obtained results are of great interest for studying the premises of chaos in pulsed solid-state lasers.

We present a functional glass coating that embed several functionalities suitable for cover glass

applications in solar energy harvesting applications, including omnidirectional anti-reflection, dynamic solar

control, and self-cleaning. Yttrium hydride oxide (YHO) and sulphated titania (SO4-TiO2) thin films were

deposited on the nanopillar structures using magnetron sputtering methods. Nanopillar terminated glass were

achieved by colloidal lithography templating methods on iron free glass, realizing nanopillar structures with

dimensions /2. The resulting nanopillar structures exploit Mie scattering for wide angle light collection.

The YHO and SO4-TiO2 films block UV light and YHO photo-darkens upon solar light absorption with and

reverts to its transparent state in darkness in reproducible manner with colour neutral spectral characters. The

results demonstrate possibilities to increase e.g. solar cell device efficiency by smart cover glass materials

without adding further control and maintenance solutions.

The controlled manipulation of optical responses from quantum emitters on the nanoscale is crucial for creating tunable light sources in nanophotonic devices. In this work, we study the coupling of a thin film made of phase-change material (VO2) with a 20 nm-thick silica layer containing Er3+ ions. We demonstrate that the thermally induced semiconductor-to-metal transition of VO2 enables the dynamic tuning of the local density of optical states near erbium emitters. This modulation enables the real-time control of Er3+ emission lifetime at the telecom wavelength (1.54 μm). We achieve a decay rate contrast of factor 2 between high temperature, when VO2 is metallic and room temperature, when VO2 is semiconductor. The experimental findings are in excellent agreement with predictions obtained using the classical dipole oscillator analytical model. A complete hysteresis cycle is measured by varying the sample temperature in the range between room temperature and 100 °C. The hysteresis parameters are consistent with those obtained by GIXRD and transmittance measurements of the VO2 layer as a function of the temperature, confirming the active role provided by the phase-change material. The results make the investigated system an optimal candidate for the development of tunable photon sources at telecom wavelength.

Erbium-doped “mixed” yttria-scandia (ScxY1-x)2O3 transparent laser ceramics were fabricated by vacuum sintering at 1750 °C from laser-ablated nanoparticles. Their absorption and mid-infrared emission properties were studied. The addition of Sc3+ induces a strong inhomogeneous spectral line broadening, modifies the crystal field and affects the distribution of Er3+ ions over C2 and C3i symmetry sites. Due to their broadband emission properties, Er:(ScxY1-x)2O3 ceramics are appealing for 2.8-µm lasers.

Depressed cladding waveguides in a Dy:YAG crystal were fabricated by femtosecond direct laser writing. Their μ-luminescence characterization in the visible revealed well-preserved emission properties in the core region, a strong material modification within the damage tracks, and an anisotropic stress field associated with ear-like side structures. The developed waveguides are promising for yellow lasers.