Conference Agenda

Hyperspectral imaging (HSI) is a very powerful tool to study artworks in a non-contact way. Nevertheless, typical HSI systems, which rely on spatial-scanning and dispersive spectrometers, suffer from high-light losses and are difficult to operate for analysing complex artworks. Here we review the capabilities of a HSI system based on TWINS, an innovative Fourier Tranform (FT) spectrometer, which allows wide-field imaging. We demonstrate how, by coupling the TWINS to different imaging systems, it is possible to achieve multi-scalar configurations from very large field-of-view (FOV) acquisition to microscopy. Further, we show how the high-collection throughput of the device allows for the sequential and fast detection of multi-modal signals’, as diffuse reflectance, transmittance, photoluminescence (PL) and Raman.

The characterization of deterioration processes in wooden artifacts is crucial for assessing their state of conservation and ensuring their preservation. Advanced imaging techniques are currently being explored to study the effect of chemical changes on the structural and mechanical properties of wood. Combined second harmonic generation and two-photon excited fluorescence (SHG/TPEF) imaging is a recently introduced non-destructive method for the analysis of cellulose-based samples. The study of age-related wood degradation based on nonlinear signal variation is a promising avenue. This work involves nonlinear multimodal analysis of naturally aged and dendrochronologically dated spruce samples. SHG/TPEF imaging and fluorescence lifetime imaging microscopy (FLIM) were used to demonstrate the influence of molecular deterioration and rearrangement of biopolymers on the fluorescence emitted by lignin and the second harmonic signal generated by cellulose. Imaging based on spectral filter detection and time-resolved analysis of the nonlinear fluorescence signal was used to delineate and potentially quantify ageing-induced morpho-chemical changes in the ultrastructure of wood cells. The analysis of cell structures by optical sectioning revealed variations between wood samples of different ages and different cell structures.

This work introduces a novel method to multivariate analysis applied to fused hyperspectral datasets in the field of Cultural Heritage (CH). Hyperspectral Imaging is a well-established approach for the non-invasive examination of artworks, offering insights into their composition and conservation status. In CH field, a combination of hyperspectral techniques is usually employed to reach a comprehensive understanding of the artwork. To deal with hyperspectral data, multivariate statistical methods are essential due to the complexity of the data. The process involves factorizing the data matrix to highlight components and reduce dimensionality, with techniques such as Non-negative Matrix Factorization (NMF) gaining prominence. To maximize the synergies between multimodal datasets, the fusion of hyperspectral datasets can be coupled with multivariate analysis, with potential applications in CH. In this work, I will show examples of this approach with different combinations of datasets, including reflectance and transmittance spectral imaging, Fluorescence Lifetime Imaging and Time-Gated Hyperspectral Imaging, and Raman and fluorescence spectroscopy micro-mapping.

The discovery of the Herculaneum papyri in the 18th century at the Villa dei Papiri has captivated scholars due to their preservation from the 79 A.D. eruption of Vesuvius and their rich historical content. These papyri, containing knowledge from Greek philosophical schools, present significant challenges for readability and interpretation due to their carbonized condition. The ERC Advanced Grant “GreekSchools” project aims to develop new protocols using optical methods to enhance text analysis, facilitating a new critical edition of Philodemus’ "Arrangement of the Philosophers." To uncover hidden texts and locate overlapping layers, we employ advanced non-invasive techniques across various spectral regions, including Macro X-Ray Fluorescence Imaging (MA-XRF), Shortwave-Infrared Hyperspectral Imaging (SWIR HSI), technical photography in the visible (VIS), ultraviolet (UV), and infrared (IR) regions and high-resolution digital microscopy in the VIS and NIR. This contribution compares various acquisition methods and image processing techniques in the NIR and SWIR regions to enhance the visualization of the writing patterns.

Throughout the 20th Century, plastics found extensive use in fashion, art, and design due to their versatile nature. However, their degradation over time poses challenges, impacting material integrity, particularly in museum collections. To tackle this issue, different scientific techniques have been employed to study polymers. In this work, a complementary multi-analytical approach is proposed to investigate the light stability of ABS compounds, selecting LEGO® bricks as reference material. The method is based on fluorescence emission and lifetime integrating point-like analysis and imaging systems to corroborate chemical and spatial information specifically addressed at the surface level. The latter has shown promising results in studying ABS objects, offering insights into degradation and aiding conservation efforts.

Micro-Spatially Offset Raman Spectroscopy (micro-SORS) is an advanced Raman technique that allows the non-destructive analysis of inner portions of cultural heritage artefacts, providing insights on their composition in a non-destructive way. The contribution delves into the methodological and technological advancements of micro-SORS at the CNR-ISPC Raman Spectroscopy Laboratory in Milan over the past decade. Developed in 2014, micro-SORS has become a versatile tool for characterizing artefacts from various historical periods and cultural contexts. Significant progress has been made in refining instrumentation and methodology, resulting in high-performance micro-SORS prototypes, including benchtop and portable systems. Key topics focus on investigating layered materials (e.g., paintings and painted objects) and studying the diffusion of conservation treatments and decay products into various substrates. The aim is to obtain information about the materials' composition, the efficacy of treatments, and the conservation state of the objects under analysis. Additionally, mapping/imaging micro-SORS has been developed to reconstruct the distribution of compounds hidden by opaque layers, such as concealed text in sealed letters. Lastly, this presentation will cover challenges associated with in-situ micro-SORS analysis, including environmental constraints and data interpretation, and will explore strategies for overcoming these.

Ultramarine Blue (UB) pigment, derived from lapis lazuli, holds a significant place in the history of late medieval and Renaissance Europe, owing to its unusually bright colour and stability. Its prohibitive price, which equalled that of gold, meant that it was only used by estimated artists. In this work we present a non-invasive, multimodal approach to the characterization of the photoluminescent properties of different variants of the pigment. The ultimate goal of this research is to propose a protocol for the identification of UB in artworks thanks to the combination of Raman spectroscopy and time resolved-photoluminescence spectroscopy and imaging.

The 1960s saw the emergence of plastic as an indispensable component in various fields, including art and design. Acrylonitrile-butadiene-styrene (ABS) is widely used by artists and designers for a range of applications including sculptures and decorative pieces. Consequently, the necessity to conserve ABS from deterioration is a crucial issue in the field of cultural heritage preservation. Many studies have highlighted the criticality of the stability of the polybutadiene component when exposed to light. We propose a new multimodal spectroscopic approach to assess the conservation status of plastic design objects. This nondestructive approach combines correlative Brillouin and Raman micro-spectroscopy (BRaMS),

external reflection IR spectroscopy and portable NMR relaxometry. BRaMS is a novel nondestructive technique in the field of heritage conservation, allowing simultaneous monitoring of chemical and mechanical changes occurring at the sample surface. The present study focused on photochemically aged LEGO® bricks made of ABS and aimed to i) correlate chemical and mechanical changes induced by light exposure and ii) introduce a surface degradation index (SDI), measurable in situ by external reflection IR spectroscopy, to assess the state of conservation of plastic artefacts. Finally, non-invasive investigations were carried out on real design objects using the MObile LABoratory (MOLAB) platform.

This study explores the use of hyperspectral imaging (HSI) to monitor the effectiveness of plasma-generated atomic oxygen (AO) treatment for non-invasive cleaning of cultural heritage object. Silk samples dyed with indigo blue, including those soiled with soot to mimic historical artifacts, were treated with plasma-generated atomic oxygen for varying durations. Using HSI with a TWINS birefringent interferometer, diffuse reflectance and light-induced fluorescence are observed. That allowed a precise evaluation of sample degradation avoiding any invasive sample extraction. This research not only contributes to the field of cultural heritage conservation but also enhances understanding of indigo colour degradation processes and the evaluation of non-invasive cleaning techniques on sensitive materials.

We propose a new spatial light modulator (SLM) concept, relying on a local thermal modification of a thick liquid crystal layer, that is optically-induced through the absorption of a control beam. This innovative thermo-optically addressed SLM, coined TOA-SLM, has shown dynamic phase control capabilities over multi-octave light spectrum, as a promising candidate for spatial or temporal manipulation of ultrafast pulses. In addition to being ultra-broadband and programmable, such a device is low-cost, large-aperture and un-segmented with a high number of control points. The construction and training of a neural network-based statistical model provides configurable design of a prototype TOA-SLM. This step, together with the ultra-broadband acceptance of the device and its ability to introduce continuous and deep phase modulation over a large aperture, opens the way for ultrafast laser aberration compensation using this new technology.

We present results that show the possibility to arbitrarily shape the

driving laser for high-order harmonic generation with a spatial light modulator

in order to control different parameters of the generated harmonics

Dark optical solitons are solutions to the nonlinear Schrödinger equation in normal dispersion media with positive Kerr nonlinearity, exhibiting a discrete π phase jump. These solitons are valuable to applications within telecommunication. Recent advancements have demonstrated the generation of two-colour bright-dark soliton pairs through cross-amplitude modulation in laser cavities, resulting in mode locking. In this study we present for the first time full field characterization of the electric field of a dark pulse. We achieved this by performing Blind Frequency Resolved Optical Gating measurements using the synchronous bright pulse as the gate pulse. The retrieved dark pulse verifies the existence of the expected π phase jump in the phase of the dark pulse, confirming theoretical predictions.

This work presents a universal seeder architecture based on filamentation and parametric amplification from an Ytterbium pump laser for the generation of pulses with versatile properties in terms of central wavelength, bandwidth, CEP, and contrast for seeding high power amplifiers based on various technologies.

We present a general temporal shaping method based on spectral phase-only modulation for ultrafast laser sources. We explain the working principle of this technique and use it experimentally to generate a rampshaped pulse at the output of a laser source delivering 30 μJ 200 fs pulses at 500 kHz. This pulse is then launched inside a multipass cell to demonstrate non-linear wavelength shifting. A spectral tunability of 11 nm around the center wavelength of 1030 nm is achieved.

Dual-comb spectroscopy combining key advantages of fast, broadband and accurate measurements has been established in the infrared as a method for the investigation of a variety of samples, more recently for the field studies of atmospheric gases with kilometer-scale absorption path lengths.

We could recently extend the application capabilities of field-deployed dual comb spectroscopy by developing a portable dual-comb spectrometer operating in the visible spectral region for atmospheric monitoring of NO2, a pollution gas of major importance. In combination with a multi-pass approach through the atmosphere, an interaction path length of almost a kilometer is reached while achieving both advanced spatial resolution (90 m) and high detection sensitivity (5 ppb).

By transposing DCS into the UV spectral region, the highly energetic UV photons can be exploited to drive electronic and rovibronic transitions in molecular (gas) species. We realized UV dual comb spectroscopy using two broadband ultraviolet frequency combs centered at 871 THz and covering a spectral bandwidth of 35.7 THz. We obtain rotational state-resolved absorption spectra of formaldehyde, a prototype molecule with high relevance for laser spectroscopy and environmental sciences in 100 µs of measurement time.

The experimental investigation of chemically and biologically relevant dynamics induced by visible or ultraviolet (UV) light requires high temporal resolution and spectroscopic techniques capable of resolving the complexity of these processes. Time-resolved photoelectron spectroscopy has proven to be a key tool for the study of these dynamics, but most studies have been conducted with a limited temporal resolution of about 100 fs. Furthermore, typical schemes employ a deep-UV probe, which limits the observation window and leads to spectrally congested traces. In this work, we present a UV pump – extreme-UV probe beamline with sub-20 fs temporal resolution, unambiguously characterized by an in-situ photoelectron cross-correlation measurement. As an example of the capability of the setup, we show a time-resolved investigation of the non-adiabatic dynamics of acetylacetone. The extreme temporal resolution allows us to resolve the passage through the first conical intersection and to identify the coherently excited vibrational modes.

Traditional amplifier-based pump-probe systems offer versatility but are often limited by their complexity and low measurement speeds, particularly when probing samples that require low excitation fluences and high sensitivities. To circumvent this limitation, we introduce a pump-probe system that leverages a novel 60 MHz single-cavity dual-comb oscillator and an ultra-low noise supercontinuum enabled by polarization maintaining all-normal dispersion fiber. The presented system can operate in equivalent time sampling mode (also known as asynchronous optical sampling) or in arbitrary optical delay generation mode. This dual-mode operation facilitates a broad range of time-resolved studies. We have employed this system to study the non-fullerene electron acceptor Y6, a compound of significant interest in solar cell development, revealing its response at various probe wavelengths with ultra-high sensitivity. The results demonstrate the system's potential to advance the field of ultrafast spectroscopy

We report an unexpected result of the anisotropy of the nonlinear optical response of carbon nanotubes, inherent to their chirality. Using a model based on the resolution of the semiconductor Bloch equations, we theoretically demonstrate that, upon irradiation with an intense linearly polarized laser pulse along the axial direction, chiral nanotubes exhibit an oscillating azimuthal current that is absent in achiral species. This current induces a magnetic field parallel to the axis of the nanotube that radiates like a loop antenna.

ADASOPS pump-probe spectroscopy is a multi-timescale technique that is spreading rapidly especially in the field of biomolecule dynamics. Based on slight variations of the laser repetition rate, it is simple to implement and can cover a time range extending from a hundred femtoseconds to a millisecond or more. We have studied the energy fluctuations associated with this approach and have proposed a method for overcoming any instabilities.

Nonlinear optics lies at the heart of classical and quantum light generation. The invention of periodic poling revolutionized nonlinear optics and its commercial applications by enabling robust quasi-phase-matching in crystals such as lithium niobate. However, reaching useful frequency conversion efficiencies requires macroscopic dimensions, effectively limiting on-chip integration with ultracompact footprints.

Here we realize a periodically poled van der Waals semiconductor (3R-MoS2). Due to its exceptional nonlinearity, we achieve macroscopic frequency conversion efficiency (0.01%-0.1%) over a microscopic thickness of only 3μm, 10−100× thinner than current systems with similar performances.

Further, we report the generation of photon pairs at telecom wavelengths via quasi-phase-matched spontaneous parametric down-conversion. This work opens the new and unexplored field of phase-matched nonlinear optics with microscopic van der Waals crystals, unlocking new applications that require simple, ultracompact technologies such as on-chip entangled photon-pair sources for integrated quantum circuitry and sensing.

Multi-pass cells, known for their efficient spectral broadening, currently face a challenge in their peak power scalability. To address this, we implemented a strategy where the input pulse was split into 8 replicas, resulting in an increased pulse energy following nonlinear compression. The used laser delivered 208 fs pulses at 1030 nm, with pulse energies reaching up to 140uJ. Using 3 calcite crystals, the input pulse was divided and passed through the MPC, achieving a spectral broadening down to a 40 fs bandwidth limit. Subsequently, the replicas were recombined using an identical set of crystals and compressed via chirped mirrors. FROG measurements revealed a duration of 43 fs. The recombination losses amounted to less than 5 % of the output energy. This method is particularly attractive and cost-effective for spectral broadening of ultrafast lasers with adjustable repetition rate.

We present a single-stage nonlinear compression of a high power, high repetition rate Yb-doped amplifier based on a gas-filled multi-pass cell (MPC). The amplifiers delivers 100 W, 570 fs pulses at 1030 nm.

At the output of the 6.15 bar Ar-filled MPC, we measure 91 W, 22.4 fs corresponding to a transmission higher than 90 % and a compression factor of 26.

In the last years, differentmethods of laser pulse post-compression have proven their efficiency. Nonlinear spectral broadening achieved when coupling an ultrafast pulse in a gas-filled multi-pass-cell (MPC) provides common pulse compression factors of 10 to 20, depending on the initial pulse duration. We report here on the compression of up to 2 mJ, 330 fs pulses of an Ytterbium (Yb) laser down to sub-20 fs (compression factor of 17), using gas-filled MPCs, at the limit of temporal pulse breakup. Numerical calculations reproducing the experiment data, and demonstrating the importance of the driver pulse profile on the shape of the broadened spectra, are discussed.

In my presentation, I will discuss the innovative prospectives presented by Free Electron Lasers (FELs) for attosecond science. Specifically, it will elucidate how attosecond metrology and spectroscopy can be implemented at seeded FELs by substituting the necessity for synchronization between the attosecond pulse train and the infrared laser pulse with a correlated examination of the single-shot photoelectron spectra.

Ultrashort light pulses can be used to manipulate electronic and optical properties of solids at extreme temporal scales, paving the way to the study of ultrafast electron dynamics. In recent years, attosecond-based spectroscopic techniques have proved to be an instrumental tool in such studies. To this end, we investigated the effects of crystal orientation on ultrafast photoinjection dynamics in germanium using attosecond transient reflectance spectroscopy (ATRS) aided by time-dependent density functional theory (TD-DFT) calculations. Our results show that ATRS is sensitive to subtle changes in the transient reflectance due to crystal orientation, although carrier photoinjection in germanium is qualitatively robust against crystal rotation, displaying similar photoinjection processes and timings at two different crystal angles.

High-order harmonic spectroscopy is a robust method for probing electron dynamics under the influence of a driving field, capturing phenomena as brief as attoseconds. It relies on the extreme non-linear process of high-harmonic generation (HHG), where intense laser pulses are directed at a material, causing it to emit high-energy photons in harmonics of the laser frequency. In this contribution we explore the possibility to generate high-order harmonics from low-dimensional crystalline solids driven under grazing incidence. We demonstrate that, in this unconventional geometry, the electron wavefunction is ejected from the solid and, subsequently, redirected to it to generate harmonics. Most appealingly, we show that the crystal’s periodicity imprinted in the electron’s wavefunction introduces a revival dynamics closely connected with the matter temporal Talbot effect. These Talbot oscillations are ultrafast (< femtosecond) and leave a distinct signature in the high-frequency harmonic spectrum, in the form of structures extending beyond the main spectral cutoff.

We explore via numerical modeling the generation of very short photon wavelengths in hollow core waveguides (HCW) filled with He gas at high pressures. Propagation of femtosecond driving pulses is first solved using a split-step method and tested against other methods. The propagation along the HCW reveals mode beating seen in quasi-periodic oscillations of the field intensity and phase which in turn will determine the single atom response to the field.

We explore both cylindrical and conical HCW in which the guide diameter varies along the propagation direction. This second configuration generates very high harmonic orders in a regime of quasi-phase matching. We found three spectral ranges which show amplification, at 3.5, 7.6, and 11-13 nm, which are of great interest given their practical applications in spectroscopy, XUV metrology and photolithography.

Ultrafast charge transfer processes in organic materials which occur in organic materials are fundamental for advancing solar energy conversion technologies. Understanding these phenomena on a short time scale induced by visible and ultraviolet (UV) light is crucial for future control and engineering of these molecules. Here, we present a novel attosecond beamline featuring Resonant Dispersive Wave emission for generating sub-3 fs tunable pump pulses in the UV region and High Harmonic Generation (HHG) in a semi-infinite gas cell for isolated attosecond pulse generation in the Extreme ultraviolet range.

In recent years, optical nanofibres have become a promising platform for trapping, manipulating and controlling atomic systems. In this work, I will highlight our recent work on the demonstration of multiphoton processes using optical nanofibres embedded in a Rb MOT for the generation of entangled photons and the excitation of Rydberg atoms for all-fibred quantum networks.

We show that step-index multimode optical fibres retain memory of the radius at which they were illuminated, despite the output looking like a seemingly random speckle pattern. We characterize this radial memory effect, and discuss its application to spatial multiplexing for data transmission.

Optical nanofibers (ONFs) are highly suitable candidates for studying Brillouin scattering, thanks to their sub-optical and sub-acoustic wavelengths dimensions. The strong confinement of photons and acoustic phonons enhances the interaction and gives rise to several Brillouin backscattering spectra. In this work, we provide an experimental method based on pump/probe interaction in the radiofrequency domain to measure the Brillouin gain at different acoustic resonances.

We present measurements of the temperature of optical microfibers self-heated by a cw laser emitting at 1.48 µm. The experimental method we have implemented is simple and enables to perform for the first time to our knowledge spatially distributed measurements along the tapers and the microfiber part. Temperature rise of more than 20 °C is measured for moderate powers (200 mW) and relatively large radii (1.45 µm). The results are confronted to a numerical model we have developed and enable to determine range of values for the couple thermal transfer coefficient/surface absorption coefficient.

Optical fibers are of great technological importance due to their well-known unique features. Metasurfaces (MSs) are inhomegeneous 2D array of optical resonators, able to impress to the impinging beam an arbitrary modulation in amplitude, phase, polarization or frequency. Their integration on the tip of an optical fiber is able to enormously expand the fiber functionalities, by endowing a simple optical fiber with extraordinary capabilities of light manipulation. MSs are able to replace traditional bulky optical components, with the great advantage of reducing the size of the devices, thus representing a key element in a multitude of applications in modern optics, including fiber communications, analog computing, optical trapping, sensing, and imaging. In this work we exploit the paradigm of the metasurfaces based on partial-phase control in order to realize OFMT for two main applications: beam splitting and light focusing. In particular, we realized several OFMT featuring beam splitting at different angles and almost equal power on the two beams, and a focusing single-mode OFMT able to efficiently focus light at few microns from the fiber end facet, without the need of a beam expander. We show the design procedure, the fabrication process and the experimental characterization of the devices.

By using our Membrane-on-Fiber technology, we can design, fabricate and transfer complex semiconductor nanophotonic structures on the tip of optical fibers. We report fiber-tip sensors of refractive index, biomolecules, electric field and pressure, combining ease of fabrication and high precision. Using a strongly-localized and narrow-linewidth nanophotonic cavity, we also demonstrate the sensing of single ultrafine particles with diameters down to 50 nm.

Here we have developed an advanced surface-enhanced Raman scattering (SERS) platform that enables the ultrasensitive, rapid and highly specific identification of tumour biomarkers in liquid biopsies. Our focus is on the detection of Thyroglobulin (Tg), the most important tumour biomarker for the diagnosis and prognosis of thyroid cancer. Specifically, SERS-active substrates fabricated by nanosphere lithography on chip or on tips of optical fiber (OF) were functionalised with Tg Capture antibodies. Gold nanoparticles were functionalized with Detection antibodies and conjugated with a Raman reporter. The sandwich assay platform was validated in the planar configuration and a detection limit of only 7 pg/ml was successfully achieved. A careful morphological characterisation of the SERS substrates allowed us to strictly correlate the coverage area with the Tg concentration. The same approach was successfully demonstrated in the washout of fine needle aspiration biopsies from cancer patients. The strategy was transferred to the Lab On Fiber (LOF) SERS platform and successfully used to detect Tg concentration. The proposed SERS-enhanced immunoassay platform has proven to be highly versatile and can be used with both microfluidic chip POC devices and SERS-OF-based optrodes to perform sensitive, specific and rapid ex vivo assays for Tg detection in liquid intraoperative biopsies.

In this contribution, we propose the use of an advanced all-optical self-heated sensing platform for highly sensitive monitoring of the volumetric water content (VWC) in the soil. The sensor is realized by properly integrating, inside a standard metallic needle, a fiber optic heating device based on core offset light coupling method and a Fiber Bragg Grating (FBG) acting as thermal monitor. The performance of the proposed device was validated through a series of measurements in the range [9 - 36] %VWC in the soil temperature range between 5 and 40 °C. Collected results have demonstrated that the presented platform is able to perform highly stable, fast and robust measurements, with time response lower than 10 seconds. The possibility of tuning the value of the injected power according to the application makes the proposed sensing solution extremely flexible and versatile for its exploitation in large areas and/or long-distance.

We investigate the potential of forward-stimulated Brillouin scattering in optical fibers to detect changes of the fiber diameter with nanometer resolution

Brillouin scattering has found extensive applications in advanced photonics functions, including microwave photonics, signal processing, sensing, and lasing. More recently, it has been employed in micro- and nano-photonic waveguides. Tapered optical fibers, due to their small transverse dimensions, exhibit a range of optical and mechanical properties that render them highly attractive for both fundamental physics research and technological applications. By employing a heat brushing technique, we can create suspended subwavelength silica rods over several centimeters with minimal loss. In contrast to standard telecom fibers, where Brillouin scattering is characterized by a single Lorentzian resonance centered at 10.86 GHz (@ 1550 nm), tapered silica fibers exhibit multiple Brillouin resonances at various frequencies ranging from 5 GHz to 10 GHz, originating from surface, shear, and compression elastic waves. Surface acoustic waves are sensitive to their environment, while compression waves efficiently convert light. Recently, we demonstrate that a large evanescent optical field surrounding the nanofiber, exibit an efficient Brillouin scattering in gas. We show drastic Brillouin scattering enhancement by increasing the gas pressure (CO2, 47 Bar) with a maximum Brillouin gain which is 79 times larger than in a SMF.

In this paper, we have presented a novel and compact bicolor Bessel beams (bi-BBs) generator based on a single-mode fiber integrated with an axicon-like microstructure (AM). The proposed design utilized two Bessel beams manifested as pump beam of circular distribution at λ=405 nm and STED beam of donut distribution at λ=532 nm. Through numerical simulations, a type of AMs has been found to support STED system light source. The influence of the AM size variance on the characteristics of bi-BBs was also investigated. With optimized AM, the bi-BBs emitted from a single-mode fiber greatly reduces the coaxial alignment difficulty of the free space STED systems and may also provide a new way to achieve mirrorless STED super-resolution systems.

We present the design of composite optical nanofibers coated with different nonlinear materials (PMMA and TiO2) for the realization of new all-solid Raman wavelength converters. Two coating processes, multilayer dip-coating and atomic layer deposition, have been successfully developed and optimized for the functionalization, inducing only relatively low losses comprised between 0.5 dB and 1.76 dB on 2 cm. Encapsulation has also been demonstrated. The Raman modal gain coefficients have been calculated to lie between 0.3 and 0.4 m-1W-1. Based on our previous results obtained with nanofibers immersed in different liquids, Raman threshold in the ns second regime should be obtained with few cm long nanofibers. This work opens the way to a new family of composite nanofibers for different applications in nonlinear optics.

We explore fiber Fabry-Pérot (FFP) resonators, a new platform for frequency comb generation We experimentally identified mirror diffraction losses dependent on the effective area of the fiber and simulated them via Fourier optics. In the nonlinear regime, a linear stability analysis of a generalized Lugiato-Lefever equation revealed optimization of reflectivity and detuning, leading to a significant reduction in the required power threshold for comb generation compared to linear regime, and to improved energy frugality. Furthermore, controlled or exploited birefringence in various experimental settings enabled the generation of Kerr frequency combs and stimulated Brillouin lasers. In this communication we propose an overview of the practical characteristics related to the fabrication and use of these resonators.

An innovative integration method was recently proposed to integrate miniaturized optical sources on the facet of an optical fiber in a monolithic fashion. Recent advancements concerning the coupling efficiency improvement will be presented.