This paper describes a prospect for broadband mid-infrared (mid-IR) highly coherent supercontinuum generation. Tellurite and chalcogenide glass with high transparency up to the mid-IR range are used as fiber materials. We successfully develop all-solid hybrid microstructured optical fibers made of tellurite and chalcogenide glass to control chromatic dispersion and demonstrate that highly nonlinear soft glass microstructured optical fibers are promising media for broadband mid-IR highly coherent supercontinuum generation.

The advances in fluorescent diamond-based magnetic field sensors have led this technology into the field of fiber optics. Recently, devices employing diamond nanobeams or diamond chips embedded on an optical fiber tip enabled achieving fT-level sensitivities. Nevertheless, these demonstrations were still confined to operation over localized magnetic field sources. A new approach of volumetric incorporation of nanodiamonds into the optical fiber core enables optical fibers sensitive to magnetic field at any point along the fiber length. We show that information on the perturbed spin state of a diamond nitrogen-vacancy color center can be transmitted over a macroscopic length in an optical fiber, in presence of noise from large concentration of the color centers along the fiber. This is exploited in optical readout at the fiber output not only of the magnetic field value, but also spatially variable information on the field, which enables the localization of its source.

Optical fibers that can sustain large elastic deformations are promising building blocks in soft robotics, medical and wearable devices, and advanced textiles. Thus far, however, the fabrication methods developed for soft optical fibers have remained unmatured. Here, we present thermal drawing as a materials and processing platform to fabricate 10s of meters-long soft, multi-material optical fibers with intriguing architectures. It offers unprecedented opportunities to realize step-index soft optical fibers, as well as photonic crystal fibers for transmission, reflection, and sensing.

We report on successful refractive index profiling of commercially available step-index and in-house made graded-index multimode specialty optical fibers by means of X-ray computed microtomography. Our results demonstrate that the latter is an advantageous technique for characterizing large core optical fibers, which allows for retrieving information about the refractive index at optical frequencies by exploiting the absorption coefficient of X-rays.

Adaptative objects based on shape-memory materials are expected to significantly impact numerous technological sectors including optics and photonics. In this work, we demonstrate the manufacturing of shape-memory optical fibers from the thermal stretching of additively manufactured preforms. First, we show how standard commercially-available thermoplastics can be used to produce long continuously-structured microfilaments with shape-memory abilities. Shape recovery as well as programmability performances of such elongated objects are assessed. Next, we open the way for light-guiding multicomponent fiber architectures that are able to switch from temporary configurations back to user-defined programmed shapes. We strongly expect that such actuatable fibers with light-guiding abilities will trigger exciting progress of unprecedented smart devices in the areas of photonics, electronics, or robotics.

Assisted by the ultimate light manipulation properties offered by flat optical devices, we developed different schemes to impart orbital angular momentum on several beams that originate wavepackets with controllable spatial and temporal distributions.

Spontaneous Four Wave Mixing (SFWM) which generates photonic pairs is studied if it is addressed by optical vortices carrying an orbital angular momentum (OAM). We show that the output beams are OAM-correlated and that the entanglement depends on the 4-level scheme used to realize SFWM.

We exploit gas-phase molecules as light-matter interface to store an orbital angular momentum (OAM) or a superposition of OAM states (OAM-based photonic qubits) carried by ultrashort laser pulses. The interplay between spin angular momentum and OAM is exploited to encode the amplitude and spatial phase information of light beams into rotational coherences of molecules. This last is restored on-demand over tens of picoseconds with a reading beam by taking advantage of field-free molecular alignment. The underlying mechanism at the origin of the storage can be interpreted by the spatial structuring of the molecular sample induced by the field. The excitation indeed produces an inhomogeneous spatial distribution of molecular alignment (amplitude & orientation) whose periodical revivals associated with the quantum beatings of the rotational wavepacket enables to restore the spatial beam structure on-demand. The strategy is successfully demonstrated in CO2 molecules at room temperature. Besides applicability as storage medium with THz bandwidth application, the use of molecules as light-matter interface opens new functionalities in terms of optical processing and versatile control of OAM fields.

Fully polarized light, cylindrical vector beams, and beams with opposite orbital angular momentum (OAM) and their superpositions are respectively represented as points on the Poincaré sphere (PS), the higher-order Poincaré sphere (HOPS) and the OAM Poincaré sphere (OAMPS). Here, we study the mapping of inner points between these spheres, which we regard as incoherent superpositions of points on the surface of their respective sphere. We obtain points inside the HOPS and OAMPS by mapping incoherent superpositions of points on the PS, i.e., partially polarized states. To map points from the PS to the HOPS, we use a q-plate, while for mapping points from the HOPS to the OAMPS, we use a linear polarizer. Furthermore, we demonstrate a new polarization state generator (PSG) that generates efficiently partially polarized light. It uses a geometric phase (GP) blazed grating to split an unpolarized laser into two orthogonal polarization components. An intensity filter adjusts the relative intensity of the components, which are then recombined with another GP grating and directed to a waveplate, thus achieving every point inside the PS. The proposed PSG offers advantages over other methods in terms of energy efficiency, ease of alignment, and not requiring spatial or long-time integrations.

Several types of super-resolution microscopy, such as Stimulated Emission Depletion (STED), Reversible Saturable Optical Fluorescence Transitions (RESOLFT) or Switching Laser Mode (SLAM) microscopies, employ Laguerre-Gaussian beams (also called vortex or doughnut beams) to obtain fluorescence information within a sub-wavelength region of the specimen under observation, thus breaking the diffraction limit and producing images of greatly improved quality. However, in general, these techniques operate on a point-by-point basis, so we need to raster scan the sample in order to build a full, meaningful image, which takes time. Parallelization of the illumination is the only way to make these microscopies more suitable for live cell imaging applications. Here, we demonstrate the parallel production of arbitrary arrays of Gaussian and Laguerre-Gaussian lasers foci suitable for super-resolution microscopy, together with the possibility to fast scan through the sample, by means of acousto-optic spatial light modulation, a technique that we have pioneered in the past in several other fields.

Plasmonic nanostructures with achiral, but asymmetric shapes can exhibit chiro-optical phenomena at the nanoscale, given that the nanostructure-light interaction symmetry is broken. Such behaviour is defined as extrinsic chirality, and it is induced by properly arranging the experimental set-up. We show measurement techniques for extrinsic chirality in low-cost, asymmetric samples with nanostructures organized in metasurfaces. We employ widely tuneable chiro-optical characterization of transmission and reflection, as well as the circular polarization degree of the transmitted signal; near-infrared range (680-1080nm) and oblique incidence allow for the detection of resonant features in extrinsic chirality. Other, unconventional experiments use photo-thermal consequences of chirality governed absorption in metasurfaces. Photo-acoustic spectroscopy directly gives circular dichroism as a differential absorption of the left and right circular polarizations exciting the sample. Photo-deflection spectroscopy gives additional information of diffraction phenomena governed by the extrinsic chirality. We showed that these techniques can monitor the extrinsic chiral behaviour of the hybrid plasmonic metamaterials. Moreover, they can be used in combination with fluorescence-detected circular dichroism to measure the emission properties of fluorescent materials.

Circular dichroism spectroscopy is a key probe of the structural and optical properties of chiral materials, however, commercial circular dichroism spectrometers are large, prohibitively expensive and rarely offer environmental control of the sample under test. Here we demonstrate two low-cost (<£2,000) and portable imaging systems controlled by our own bespoke open-source control software which are capable of spatially mapping the circular dichroism of chiral solid state films. By coupling these imaging systems with a temperature controlled stage, we show that we can rapidly identify the thermal processing conditions required to maximise circular dichroism in chiral solid state films by measuring circular dichroism in situ during thermal annealing of a sample under test. The accuracy and spatial resolution of these circular dichroism imagers are cross-compared against our previous studies using an existing circular dichroism imaging system at the Diamond Light Source and are shown to be in good agreement, with a sensitivity down to 250 mdeg and a spatial resolution of 100 μm.

Lattice resonances, collective electromagnetic modes supported by periodic arrays of metallic nanostructures, produce very strong and spectrally narrow optical responses. Recently, there has been significant effort devoted to exploring their chirality (dissymmetric response to right- and lefthanded circularly polarized light) in arrays built from complex unit cells. In this communication, we investigate the lattice resonances of square bipartite arrays in which the relative positions of the nanostructures can vary in all three spatial dimensions, i.e., 2.5- dimensional arrays. Despite the achirality of their unit cell, the lattice resonances supported by these systems can display an almost perfect chiral response and very large quality factors due to the constructive and destructive interference between the electric and magnetic dipoles induced in their nanostructures. Our results provide the fundamental understanding to achieve strong chiral lattice resonances in structurally achiral 2.5-dimensional periodic arrays.

Exotic light fields combining non-trivial spin and angular momentum may not be eigenstates of either the spin or orbital angular momenta operators. For these fields, it is relevant to define a Generalized Angular Momentum operator of which they are eigenvectors. Their associated eigenvalues can take, depending on the case, non-integer values.We report that this new quantity is conserved via non-linear phenomena, such as High Harmonic Generation.

Understanding high-order harmonic generation (HHG) from solid targets holds the key of potential technological innovations in the field of high-frequency coherent sources. Solids present optical nonlinearities at lower driving intensities, and harmonics can be efficiently emitted due to the increased electron density in comparison with the atomic and molecular counterparts. In addition, crystalline solids introduce a new complexity, as symmetries play a role in the anisotropic character of the optical response. An extraordinary playground is, therefore, the scenario in which solids are driven by vector beams, since crystal symmetries can be directly coupled with the topology of the driving laser beam. In this contribution we analyze the topological properties of the HHG radiation emitted by a single-layer graphene sheet driven by a vector beam. We show that the harmonic field is a complex combination of vortices, whose geometrical properties hold information about the details of the non-linear response of the crystal. We demonstrate, therefore, that the analysis of the topological structure of the harmonic field can be used as a spectroscopic measurement technique, paving the way of topological spectroscopy as a new strategy for the characterization of the optical response of macroscopic targets.

We review here our recent work in achieving mid-infrared (MIR) fibre lasing beyond 5 microns wavelength in Ce3+-doped selenide-chalcogenide fibre, as well as the observed photoluminescence in samples of the same composition but in particulate and bulk glass form as well as unstructured fibre and in the SIF (step index fibre) in which fibre lasing took place.

The passive Q-switching performance of an in-band pumped Dy-doped fluorozirconate fibre laser emitting around 3.1 um is investigated. Passively Q-switched laser operation is demonstrated employing semiconductor saturable absorber mirrors. Stable operation is achieved, with a minimum pulse duration of 464 ns, a highest repetition frequency of 210 kHz and peak pulse powers up to 3 W.

We demonstrate an athermal Brillouin strain sensor using heavily GeO2-doped optical fibers. We also report nonlinear evolution of Brillouin temperature sensitivity as a function of wavelength and strong Brillouin gain in these fibers.

We experimentally demonstrate that simple tapered Ge-Se-Te glass rods with femtosecond pumping enables efficient multi-octave mid-infrared supercontinuum generation, from 1.7 to 16 µm, while keeping an excellent spatial beam profile.

We present the complete (analytical, numerical and experimental) analysis of intermodal-vectorial four-wave mixings proccesses in birefringent fibers. We analyze phase-matching condition and overlap coefficients to indicate possible processes. Then, we demonstrate multiple four-wave mixing processes in LP01 and LP11 modes numerically and experimentally. Finally, we extend theoretical analysis to account higher order modes: LP02 and LP21.

The amount of transverse orbital angular momentum (OAM) carried by the spatiotemporal

optical vortices (STOVs) is being hotly debated. In this contribution I unveil the mystery of the amount of total, intrinsic and extrinsic transverse OAM carried by STOVs. They do not carry any total transverse OAM about a static transverse axis crossing the STOV center. Yet, STOVs carry a transverse OAM about a moving transverse axis crossing the STOV center permanently, which is identified with the intrinsic OAM, and an opposite extrinsic transverse OAM about the fixed axis. These results raise questions about the interpretation of second-harmonic and high-harmonic experiments or simulations with STOVs, and the capability of STOVs to transmit OAM to particles. Other advances such as observation of vortex splitting and topological charge flipping of high-order STOVs in free space and in dispersive media, and the transverse torque exerted by optical elements will be discussed.

Moving from diffractive optics to metalenses, novel tools for structuring light are provided for the integration in compact optical layouts. Here we propose new metaoptics designed for light shaping into structured beams implementing on-demand vectorial configurations. Different optical layouts are achieved in order to generate orbital angular momentum (OAM) vector beams with different shape and peculiarities.

Airy wave packets constitute a very peculiar type of structured light: during their propagation, their transverse profile undergoes a self-accelerating displacement while it remains shape invariant. They are thus the only non-dispersive beam-type solution to the Helmholtz paraxial equation in free space. Such properties are possible by virtue of their infinite power content. However, experimentally, Airy beams can only be reproduced in an approximate manner, with a limited extension and hence a finite power content. To this end, different cutoff procedures have been reported in the literature, based on a convenient tuning of the transmission properties of aperture functions. In this Communication, we present and discuss our latest advances in the analysis of the effects that convolving an Airy beam with different aperture functions have on their propagation properties. More specifically, we make use of a trajectory-based methodology, which allows us to analyze and explain the beam propagation in terms of trajectories directly connected with the beam local phase variations.

We demonstrate spontaneous emission of discretized conical wave when an ultrashort pulse propagates nonlinearly in a multimode fiber. Our theoretical predictions are experimentally and numerically confirmed, providing a general understanding of phase-matched radiations emitted by nonlinear waves in multidimensional dispersive optical system.

We present a complete Mueller matrix (MM) imaging polarimeter based on liquid-crystal retarders and a pixelated polarization camera. The polarimeter is calibrated and optimized at the pixel level. Therefore, the instrument is applied for the precise characterization of optical components used for the generation of structured light, like patterned retarders and patterned polarizers.

UVA one-photon hyperspectral light sheet imaging was performed here to capture and reconstruct three dimensional metabolic maps of mouse embryos during development. We explored numerically and experimentally the advantages of phasor-based hyperspectral approach for detecting embryo metabolism with a single wavelength excitation compared to the conventional detection approach using bandpass filters.

In this work we present a microscope on a chip for automatic structured light sheet imaging of single cells. This integrated platform has been fabricated by femtosecond laser micromachining in glass substrates and it encompasses integrated optical elements such as waveguides, lenses and beam splitters as well as a microfluidic channel for sample delivery. Processing fluorescent cells, we have proven enhanced image resolution, automatic and continuous imaging as well as device ease of use

Root hairs are a delicate single-cell system whose growth is regulated by a fine mechanism characterised by the presence of a tip-high Ca2+ gradient that shows regular oscillations in growing root hairs. We show a method based on the use of Light sheet fluorescence microscopy (LSFM) which allows the quasi-physiological analysis of Arabidopsis thaliana plant roots hairs with excellent spatial and temporal resolution over a wide field of view. We show how the healthy growing root hairs are linked to precise oscillations and how a disruption of this mechanism can be associated to specific genes.

Minimally invasive endoscopy using coherent fiber bundles shows great potential for numerous applications in biomedical imaging. With a diffuser on the distal side of the fiber bundle and computational image recovery, single-shot 3D imaging is possible by encoding the image volume into 2D speckle patterns. In comparison to equivalent lens systems, a higher space-bandwidth product can be achieved. However, decoding the image with iterative algorithms is time-consuming. Thus, we propose utilizing a neural network for fast 2D and 3D image reconstruction at video rate. In this work, single-shot 3D fluorescence imaging with an ultra-thin endoscope is demonstrated, enabling applications like calcium imaging for in vivo brain diagnostics at cellular resolution.

Scanning fluorescence microscopes can image large tissues at the diffraction-limit. Scanning systems are also used for manipulation such as laser severing or optogenetic activation.

The conventional approach to image tissues with a scanning microscope involves scanning the entire bounding box enclosing the tissue, plane by plane, which is time-consuming and results in a high light dose.

We have developed a “smart” microscope that adapts its scanning scheme to the morphology of embryonic cell sheets, with no prior knowledge of the structure of interest. The surface of the tissue is first delineated from the acquisition of a very fractional scan of sample-space, using a robust estimation strategy. Subsequent high-resolution imaging can then be restricted to this targeted structure of interest, yielding a ~20-fold reduction in the scan path and, thus, an equivalent reduction in light dose and increase in speed. Additional scan path reduction can also be obtained using a propagative scanning approach. The resulting reduction in light dose (order of magnitude) is highly beneficial in terms of photobleaching.

We demonstrate the efficacy of our smart-scanning technique imaging Drosophila embryos and demonstrate how it can also be employed in a smart dissection scheme to make precise cuts on large non-planar tissues.

Evaluation of disease models is facilitated by live imaging which can be used to follow the behavior of the model during disease evolution, and when comparing before and after therapeutic intervention. When exploring in vitro samples for disease modeling in culture, there is a need for live, 3D, non invasive, real time, label free, subcellular resolution, dynamic, longitudinal imaging, which is currently lacking from the microscopy toolkit. Dynamic full field optical coherence tomography meets these needs and shows promise as a next generation tool for 3D live microscopy. Full-field optical coherence tomography is an interferometric technique to image transverse planes inside a sample in one shot, thus allowing distortionless rapid en face and volumetric imaging. Dynamic full field OCT is an evolution of full field OCT, where a series of frames is collected by the camera and the contrast generated by natural movements of subcellular organelles within the sample is revealed. Here, we present a new dynamic full field OCT module that may be interfaced to commercial microscopes, designed for use by biologists for long term applications in culture conditions. We present its application to models of disease in 2D and 3D samples.

A low-powered, non-invasive digital holographic microscopic imaging technique for embryo quality assessment is presented. Two groups of 2 cell-stage embryos cultured in media of different lipid concentrations have been characterized with digital holographic microscopy for lipid aggregation. The study suggests refractive index measurements are reflective of the lipid and dry mass content in embryos thus making DHM a prospective label-free diagnostic tool for quality assessments in assisted reproduction.

It has recently been discovered that biological live cells can behave like optical microlenses.

This has opened a new path towards future disruptive scenarios with the possibility of using such biolenses for the next technological developments in optics and photonics. Live cells can be employed and exploited as optical components for incredible applications ranging from simple imaging, to soft matter manipulation and biomedical diagnosis. In fact, the optical properties of such biological lenses can reveal new biomarkers useful for medical diagnosis. Different examples of application of biolenses will be illustrated and discussed. Furthermore, a new perspective for engineering biolenses to tailor their photonic properties will also be presented. Furthermore, it will be demonstrated that in-flow staining-free cytotomography based on digital holography allows for a complete and accurate 3D characterization of biolenses.

Whether host phenotypic alterations induced by parasites are reversible or not is a core issue to understand underlying mechanisms as well as the fitness costs of infection and recovery to the host. Clearing infection is an essential step to address this issue, which turns out to be challenging with endoparasites of large size relative to that of their host. Here, we took advantage of the lethality, contactless and versatility of high-energy laser beam to design such tool, using thorny-headed worms and their amphipod intermediate host as a model system. We show that laser-based de-parasitization can be achieved using blue laser targeting carotenoid pigments in Polymorphus minutus but not in the larger and less pigmented Pomphorhynchus tereticollis. Using DNA degradation to establish parasite death, we found that 80% P. minutus died from within-host laser exposure. Survival rate of infected gammarids to laser treatment was higher than uninfected ones. The failure to kill P. tereticollis was also observed with nanosecond-green laser, an alternative laser source targeting lipid. We discuss the possible causes of amphipod death following parasite treatment and highlight the perspectives that this technology offers.