In this talk we will discuss how to engineer the dispersion relation of photonic platforms to provide robust propagation of classical and quantum states of light. In the first part, we will unveil how to leverage the interaction of nonlinearity with higher orders of dispersion to create novel types of solitons, wave packets that propagate unperturbed for long distances. These objects have advantageous energy-width scaling laws with respect to conventional nonlinear Schrodinger solitons and show promise for applications in ultrafast lasers and integrated frequency combs. Subsequently, we will cover recent developments in topological quantum photonics. Topological photonics studies topological phases of light and leverages the appearance of robust topological edge states. We will emphasize our experimental demonstration of nonlinearly generated and topologically protected photon pairs and path-entangled biphoton states in silicon waveguide arrays. Further, we will detail our latest experiments demonstrating entanglement between topologically distinct modes, highlighting topology as an entanglement degree of freedom.

Holography encodes information using classical light interference with applications ranging from microscopy to data storage. Quantum entanglement enables information processing with capabilities beyond technology based on classical principles. Here we introduce a holographic imaging concept that is conditioned on the coherence, and thus the entanglement, between the qubit terms in a quantum entangled photon state. By harnessing the nonlocal properties of entanglement, we remotely reconstruct an image encoded in the phase of spatial-polarisation hyper-entangled photons. The nonlocal nature of our measurements removes the need for path overlap, resulting in insensitivity to mechanical instabilities, while polarisation encoding provides robustness against random phase disorder. Furthermore, the measurement of correlations removes the sensitivity to the presence of stray light.

Space-time (ST) wave packets are pulsed beams endowed with tight spatio-temporal spectral correlations, whereby each spatial frequency is associated with a single wavelength resulting in propagation invariance at an arbitrary group velocity. Previously, our group introduced an experimental methodology to synthesize 2D ST wave packets, i.e. light sheets, based on 2D pulse shaper. Here, we demonstrate a new experimental method to synthesize ST wave packets localized in all dimensions, including 3D space and 1D time. We show that 3D ST wave packets propagate longer distances without spreading compared with traditional Bessel beams, and propagate at subluminal and superluminal group velocities.

Optical tweezers normally rely on the intensity gradient force to trap and manipulate microscopic objects in the transverse plane of a laser beam. The phase gradient of light provides a new degree of freedom to create transverse optical force on the trapping plane, which has been applied to control micro- and nanoparticles. Here we introduce holographic beam shaping methods to create complex light with structured intensity and phase, and demonstrate versatile optical nano-manipulation, such as optical trapping, sorting, and transporting of nanostructures by dynamically sculpting the phase profile of light.

The optical train of microparticles waveguide the light and stabilized itself due to strong optical and hydrodynamic forces. Particles develop one after another from the reservoir in direction of light propagation similarly to a chain developing from a spool or a train. We experimentally study the effect and numerically evaluate the forces acting on micorparticles in the train. When number of particles in reservoir is small we observe rapid shooting of microparticles like from the optically powered cannon.

Optical signaling through bio-soft matter is an emerging area of interest for biomedical applications. However, modern communication protocols require high capacity OAM, Polarisation and wavelength multiplexed signaling. Utilizing nonlinear optical effects, we investigate the conservation of polarization and orbital angular momentum through self-trapping and pump/probe coupled waveguides of light in sheep red blood cell suspensions at 532 nm and 780nm wavelengths. This study provides a basis for future exploration for signaling in soft matter systems.

The manipulation of the transverse profile of light beams is ubiquitous in optics. However, the independent control and shaping of copropagating transverse spatial modes, i.e. spatial mode multiplexing, is a complex task. In recent years, a number of technologies have emerged, each tailored for different propagation mediums. We will give a thorough introduction to this topic, from its mathematical formulation to the different implementations available today, focusing on free-space shaping. We will present a few applications of this technology, both in the classical and quantum domains, focusing on the particular challenges brought by it, such as cross-talk.

The development of high-quality photonic sources of high-dimensional entanglement and techniques for their manipulation is crucial for the advancement of quantum technologies. We present an efficient technique for generating and characterizing high-dimensional spatially entangled two-photon states with a record quality, dimensionality, and measurement speed. We demonstrate how to precisely manipulate such states by tailoring reprogrammable optical circuits in complex scattering media consisting of off-the-shelf multimode fiber and spatial light modulation. Our techniques open a clear pathway for the adoption of high-dimensional quantum states of light in the high-capacity, noise-robust quantum networks of tomorrow.

This talk will describe new microscopy methods that use computational imaging to enable 3D phase (refractive index) and 3D fluorescence measurements in samples that are thick or incur multiple scattering, such as embryos or whole organisms. We use image reconstruction algorithms that are based on large-scale nonlinear non-convex optimization to model the multiple scattering effects of light passing through the sample, and discuss end-to-end learned designs for optimizing the hardware configurations.

We demonstrate a device capable of controlling simultaneously all the degrees of freedom of a light beam (spatial/polarisation and spectral/temporal, 38,000 spatiotemporal modes are fully controlled through the C-band), after propagation through a multimode optical fiber that adds extra mode coupling. For this, we have combined a polarisation-resolved multi-port spectral pulse shaper (control of 1D spatial/polarisation and spectral modes) and a multi plane light conversion device (conversion 1D to 2D spatial/polarisation modes). The ability to deliver accurate volumetric light fields could be applied to control both linear and non-linear optical processes.

We used spatial light modulation to deflect coherent light beams into trajectories specified by gravitational lensing. We programmed symmetric and asymmetric lensing objects, including adding orbital angular momentum. In the far field we observed Einstein rings and arcs for symmetric lensing objects, and various types of Einstein arcs for asymmetric lensing objects, similar to what is seen in astronomical observations. In the near field we observed the caustics produced by gravitational lensing, not possible in astronomical observations, which consisted of Bessel patterns for symmetric objects, and Mathieu-like patterns and astroids for asymmetric objects.

A significant limiting factor for orbital angular momentum (OAM) based free-space communication is the unavoidable signal degradation caused by atmospheric turbulence. Its main effect, in fact, is to induce crosstalk between the various OAM states, thus introducing additional noise and rendering the detection of different OAM states quite challenging. In this work, we consider partially coherent, self-focusing fields carrying OAM beams. We then compare their performance through turbulent atmosphere with that of perfectly coherent vortex beams. We show how the innate self-focusing character of partially coherent beams results in a better resilience against turbulence-induced noise than their coherent counterparts.

The conventional way of generating Bessel beams (BBs) is based on axicon and other diffractive optical elements such as light modulators. These methods involve space-consuming optics. To overcome this limitation, over the past years, efforts were made to create BBs using miniaturized optics and generation of BBs directly from optical fibers. We propose a novel photonic structure 3D micro-printed on the end-face of an optical fiber, generating BBs of various orders. With our approach, we report for the first time the generation of high-order BBs from optical fibers. The results showcase Bessel beams ranging from orders zero- to 20.

Metasurface technology has allowed the use of ultrathin optical materials to manipulate the amplitude, phase, and polarization of light, leading to a versatile platform for digitising optical holograms with nanoscale resolution. To date, however, the bandwidth of a metasurface hologram has remained too low for practical use. Recently, twisted light holography was introduced, opening the possibility of storing holographic information in different OAM modes. We present the design and 3D laser nanoprinting of a large-scale complex-amplitude metasurface for ultrahigh-dimensional OAM-multiplexing holography in momentum space. Such a metasurface hologram allows lensless reconstruction of a record high number of 60 independent holographic images.

Speckle patterns are sensitive to wavelength variations, and can be used to measure such variations. Recently, a new way of producing speckles have been introduced, using an integrating sphere. Here, we derive a general model predicting the change occurring in a speckle pattern as a result of a generic transformation in this particular geometry. Applying this model to a wavelength variation, we show that the speckle sensitivity is mainly governed by two parameters: the radius and surface reflectivity of the sphere. We show analytically and experimentally that integrating spheres offer sensitivity four orders of magnitude above that of commonly-used multimode optical fibres offering excellent prospects for speckle metrology.

We present a computational study of the trapping, packing and dynamics of clusters of Rayleigh particles in Bessel beams. We examine the effect of beam order on the cylindrical packing arrangements of the clusters. In addition, we explore the influence of the orbital angular momentum of the Bessel beam, on the nature of the packing arrangements formed and draw comparisons with the confining effect of a fluid vortex.

In this paper the use of a patterned surface to create an optical conveyor for spherical, and near spherical particles is explored. Using a surface constructed of a repeating micron-sized motif, we simulate the effects of moving a particles in the near micron regime above the surface. To reduce optical calculation overheads, a fluid index matched to the substrate of the meta-surface is used, as this allows use to ignore scattering effects due to the presence of a substrate. We also explore optical force changes in the axis perpendicular to the surface that occur due to changes in size of the particles, and the choice of incident wavelength.

In this presentation, we will outline a method to detect the position of fiber bends in both few-mode and multi-mode fiber by measuring the distortion of OAM modes during propagation. The complex mode coupling that occurs can make it difficult to directly infer what caused the optical distortions one observes. Therefore, we implement a novel optical element enhanced Machine Learning approach that combines all-optical mode transformation with a Support Vector Machine Learning algorithm to accurately determine the location of a fiber bend with greater than 87% accuracy in MM fiber and 68% in FM optical fiber.

The chirality of electromagnetic beams is a property relevant to various nanophotonic applications, yet this property is challenging to characterize at the nanoscale. We have found that electromagnetic beam chirality can be probed through the optical force exerted on a cantilevered, chiral tip. We demonstrate that the differential force, i.e. the difference in the force induced by a focused beam and an auxiliary beam of opposite handedness, exhibits a direct correspondence to the beam’s time-averaged helicity density. Measurement of the differential force yields spatially resolved maps of the helicity density of tightly focused beams with sub-diffraction limited resolution.

This video was recorded for SPIE Photonics West 2022

We demonstrate the laser induced forward transfer of fluorescent dye solution thin films by employing a single 532-nm nanosecond optical vortex pulse. Upon irradiating the laser pulse, a single microdroplet is ejected from the donor film, and it is forwarded onto a glass substrate a few hundreds of micrometers away from the film. The optical vortex enables us to print well-aligned microdots with the same diameter of 30 µm on the substrate, whereas a conventional Gaussian beam prevents the production of microdots in uniform size. The optical vortex laser induced forward transfer allows the development of micro-patterning of functional materials.

We demonstrate a non-Hermitian system by introducing topological dynamics in coherent laser arrays. It consists of a large set of mutually interacting optical vortices subject to arbitrary topological transformations realized by metasurfaces in a closed environment. Like atoms in a crystal, the vortices are arranged in a regular lattice producing Bragg diffraction peaks. Prior art focussed on demonstrations of single vortex sources employing concepts from non-Hermitian and topological photonics to add charge reconfigurability and to mitigate manufacturing fault effects. We extrapolate these concepts to vortex arrays that demonstrate tunability and robustness akin to those of topical single vortex sources.

The digital age and advances in engineering have triggered a wave of low-cost, accessible, and customisable microscopes. Already utilised for outreach, education and field work, the potential of these devices extends beyond accessible prototypes, and into microscopy in research and medical settings. The open-source, 3D-printed OpenFlexure Microscope is one such device, with development focused on supporting the diagnosis of malaria in sub-Saharan Africa. This project motivated the redesign and verification of core functionality, to ensure that automated scanning, focusing, and tiling of blood samples is sufficiently reliable to support the workflow of frontline healthcare professionals. This talk will cover examples of "smart" microscopy, where on-line analysis of data is used to identify and correct errors in the experiment.