By using the Generalized Lorentz-Mie Theory (GLMT), which was successfully adapted from optics to acoustics, we present a thorough parametric study of acoustic forces in a standing-wave levitation trap, which allows us to identify the most relevant parameters of the levitation devices, while exploring the size ranges of the objects that can be acoustically levitated in these kinds of traps. We show that particles can be trapped either in pressure nodes or antinodes, depending solely on their size. This is analogous to the particle size-effect found in optical traps with complex light potentials. We present theoretical and experimental results for airborne levitation that are in excellent agreement.

We present a novel method for characterising nanoparticles through analysis of their light scattering. We examine the resultant angularly resolved Rayleigh scattering patterns by aligning and orienting single optically levitated nanoparticles in a vacuum with trapping light. We compare our experimental findings with simulations of the Rayleigh scattered field, which allow us to determine in-situ the morphology of individual nanoparticles. While primarily utilized in low-damping environments, this method can also be applied in traditional overdamped fluids, paving the way for precision measurements of single isolated nanoparticles.

Sculpted light refers to the generation of custom designed light fields. These light fields can be applied in many diverse fields ranging from interrogating single atoms or atom assembly to using these fields for optical micromanipulation and optical tweezers as well as creating new quantum devices and sensors. We consider here the study and application of light with structured intensity, polarization and phase. These sculpted lights can be used for intricate studies of light -matter interactions in a variety of environments. I will describe their use in transfer of transvers angular momentum of light and in studies of inertia.

We will discuss some of our recent results on fractional scalar and vector vortex beams representing the Hilbert Hotel paradox. Using full Poincare Bessel beams (FPB), we showed that one can create an infinite series of C-point singularities. We have also devised a novel method to measure the polarization coverage of Poincare beams and showed that the FPBs are the superposition of an infinite number of Poincare beams.

Topologically protected optical quasiparticles with sophisticated vectorial structures, i.e. analogous optical skyrmions, have attracted much attention, and they are classified into different topological textures, such as Neél-, Bloch-, and anti-skyrmion. However, the generation and application of analogous optical skyrmions are still an emerging topic in their infancy.

We herein propose a compact and robust approach to generate analogous optical skyrmions based on a single-path polarization interferometer with a spatial light modulator (SLM). Also, we report on the first demonstration of analogous optical skyrmions induced exotic surface reliefs onto azopolymers associated with the trans-cis-trans isomerization reaction.

We develop a simple, robust method of customizing the intensity statistics of laser speckles and introducing non-local correlations among the speckle grains. The tailored speckle patterns exhibit radically different topologies and varying degrees of spatial order. The various families of speckles are created by encoding high-order correlations into the phase front of a monochromatic laser beam with a spatial light modulator. Recently, we generate volumetric speckles with distinct tailored intensity statistics on multiple designated planes. The ability to design 3D speckle statistics opens many possibilities: three-dimensional imaging and sensing, optical trapping and manipulation.

Highly multi-mode media convert a coherent input field’s spatial profile into a granular speckle patterns. These speckle patterns are heavily dependent upon properties of the multi-mode medium and the input light field. Examining these speckle patterns enables extraction of these parameters; numerous spectrometers have been demonstrated by analyzing speckle. This is germane to precision measurement of optical wavelength, which is crucial in many applications including: laser spectroscopy, optical sensing, and laser locking. To the best of our knowledge we have demonstrated, for the first time, a transmission matrix method (TMM) speckle spectrometer capable of resolving the hyperfine structure of rubidium at 780nm. We compare this with other TMM speckle spectrometers in literature as well as discussing the advantages and disadvantages of the transmission matrix technique.

Numerous areas of photonics including optical microscopy, semiconductor analysis and lithography and fundamental science increasingly aim for precision at or below the nanoscale. As a result, the ability to perform sub-nanometric displacement and position sensing is highly desirable. We demonstrate that the speckle patterns generated by multiple reflections of light inside an integrating sphere provide an exceptionally sensitive probe of displacement. We use an integrating sphere divided into two independent hemispheres, one of which is free to move in any given direction. The relative motion of the two hemispheres produces a change in the speckle pattern from which we can analytically infer the amplitude of the displacement. Our approach results in a noise floor of 5 pm/ Hz (λ /160, 000) above 30 Hz in a facile implementation, which we use to measure oscillations of 17 pm amplitude (λ /50, 000) with a signal to noise ratio of 3.

Until recently, work in quantum optics focused on light interacting with bound-electron systems such as atoms, quantum dots, and nonlinear optical crystals. In contrast, free-electron systems enable fundamentally different physical phenomena, as their energy distribution is continuous and not discrete, allowing for tunable transitions and selection rules.

Recent theoretical and experimental breakthroughs involving quantum interactions of free electrons spawned an exciting new field: free-electron quantum optics. We developed a platform for exploring free-electron quantum optics at the nanoscale, and used it to demonstrate the first coherent interaction of a free electron with a photonic cavity and with the quantum statistics of photons.

These capabilities open new paths toward using free electrons as carriers of quantum information. Free electrons emerge as quantum optical sources for desired photonics states used in fault-tolerant quantum computation and communication such as Schrodinger cat states and GKP states.

Concepts of quantum optics with free electrons also promote new modalities in electron microscopy. We demonstrated the first instance of coherent amplification in electron microscopy. Our vision is to develop a microscope that can image coherence, going beyond conventional imaging of matter to also image the coherent quantum state of matter and probe quantum correlations between individual quantum systems.

When light interacts with media down to the nanoscale, it is spatially structured, e.g., in its amplitude, phase, or polarization, depending on media properties. This interaction can be used for various applications: For instance, we can advance standard imaging by extracting usually inaccessible information from nonparaxial structured light, such as the 3d orientation of nanoscale emitters. Moreover, we can advance quantum cryptography by 3d polarized structured light, encoded and decoded by an inversely designed integrated emitter structure. We will provide insights into these applications, showing the benefit of structured light meeting functional nanostructures.

Entangling photons in the orbital angular momentum (OAM) degree of freedom, demonstrated over 20 years ago, yields a promising pathway for increasing the dimensionality of quantum sources, of utility in high-dimensional communications as well as in efficient quantum computing algorithms in higher-dimensional Hilbert spaces. An efficient integrated-optic means of achieving this has, however, eluded the community thus far.

One potential solution to this problem may be found by exploiting the newly discovered phenomenon of topological confinement, which has yielded a multimode platform with as many as 60 stable OAM modes in optical fibers. This provides for a plethora of spontaneous four-wave mixing phase matching possibilities enabling control not only over the wavelengths at which the photon pairs can be generated, but also over the shapes of their joint spectral densities, ranging from correlated, uncorrelated, to anti-correlated.

This talk will describe recent experiments aimed at the development of compact, single-aperture devices whose biphoton emissions can be engineered to exploit the spatial dimension of light.

We prepared Poincare beams consisting of non-separable superpositions of polarization and spatial modes bearing orbital angular momentum. A geometric phase shifter varied the phase between the component polarization modes. As a consequence, the output beam projected by a polarizer carried a spatial pattern that rotated with an angular speed proportional to the difference in topological charge of the component modes and the rate of change of the phase. We investigated the encoding of information in the angular speed of the patterns for the purpose of communications. The detection of the encoded rotation consisted of two photodiodes located off center to the pattern and forming a shallow angle from the center of the beam. Their signal was used to determine the angular speeds of the patterns. We used various types of Gaussian, non-diffracting and Einstein beams in proof-of-principle communication schemes.

The beautiful topological structure of the retardance distribution in a glass window with inhomogeneous stress (a stress-engineered optic or SEO) leads to a variety of intriguing optical physics, optical engineering, and applications. I will give a bit of the history of stress engineering applied to complex light fields, review some of the work related to polarization and polarization measurement, describe Full Poincaré Bessel beams formed from an SEO, and discuss current and future applications for single-shot characterization of complex fields such as those used in inertial confinement fusion experiments.

The emerging field of “materials that compute” aims to mimic the intelligent responsiveness of biological systems – without the need for external electronics or processors. Examples are tactility, vision, camouflage, contractility and flight where complex natural sensors such as skin, eye and muscle seamlessly adapt to environmental stimuli through exquisitely programmed response sequences. In this talk, I will describe how our group contributes to this objective by applying our understanding of unusual (nonlinear) forms of light and their extraordinary behaviours in soft light­responsive polymer materials.

With an index of refraction approaching 9 at microwave frequencies, water is a high-index dielectric material suitable for studying morphology-dependent resonance (MDR) analogs of metallic plasmonic hotspots. We use experimental, analytical, and computational approaches to study MDRs in aqueous dimers, paying particular attention to formation of evanescent axial hotspots. We use hydrogel beads and thermal imaging, along with FEM simulations to explore polarization, orientation, and size-dependence in MDR hybridization. A novel analytical approach involving vectorial addition of spherical harmonics of monomer MDRs provides geometric insight into which modes most strongly interact to yield strong subwavelength electromagnetic hotspots in aqueous bispheres.

Sculpturing light pulses spatiotemporally with sophisticated controls of various degrees of freedom is one of the powerful tools for material interrogations and manipulations, as well as information transmission and processing. Even though exotic light fields are part of Maxwell’s solutions or wave equation’s eigenmodes, their presence and richness still surprise us with new or renewed physical insights and understandings. Also, the diversity of the modes and states of such light fields has inspired us to pursue their potential new applications, from information technologies to light-based sensing and imaging. In this talk, I will briefly review the recent progress in spatiotemporal light fields and then focus on our recent experimental efforts to generate, manipulate, and characterize such light pulses from strong-field (or high-field) to single photon levels.

The extensively employed technique of Stimulated Raman Scattering (SRS) has found widespread application in the domain of biomedical imaging. Typically, the CH band is harnessed for the identification of biomolecules. Nonetheless, the task of distinguishing between CH2 and CH3 bonds presents an ongoing challenge. In the present investigation, Circularly Polarized Stimulated Raman Scattering (CP-SRS) illumination was employed. This was carried out to explore the impact of polarization on the differentiation of CH vibrational modes. Intriguingly, it was observed that circular polarization notably repressed CH2 bonds in contrast to CH3 bonds. This selective effect facilitated the visualization of pure protein, eschewing the complexities posed by protein-lipid compounds. This unique unmixing approach significantly enhances the chemical specificity of SRS imaging. As a result, it holds remarkable implications for applications such as metabolic imaging and beyond.

Rapid beam scanning as a consequence of transverse mode-locking (TML) is demonstrated by mode conversion in an empty optical resonator. Phase-locked spectral components of an incident beam are matched to transverse mode resonances of the conversion resonator. This way, a TML beam is generated by simultaneous transmission of all spectral components. This can also be understood as conversion of a longitudinal mode-locked to a transverse mode-locked state, or equivalently, conversion from temporal amplitude modulation to spatial beam scanning. The Pound-Drever-Hall (PDH) scheme is used to stabilize the incident beam's optical frequencies to a compound transverse mode resonance, showing that continuous emission of a well-defined transverse mode-locked state is possible.

Dichroism is often associated with chiral systems and circularly polarized light that is used as a chiral reagent. The two mirror images of a chiral systems are discerned by studying the propagation of left- and right-circularly polarized light. Here we demonstrate (a) efficient chiral sensitivity with linearly polarized helical light beams carrying an orbital angular momentum, and (b) that dichroism is intrinsic to achiral systems including amorphous materials. We model helical dichroism by considering induced multi-pole moments in light-matter interactions. Our research challenges the conventional wisdom that dichroism does not exist in achiral systems, enables to control light-matter interaction and opens new opportunities in chiroptical spectroscopy.

We generalize the concept of optimally chiral light (OCL), which encompasses all fields with maximum chirality at a given energy density, such as circularly polarized light (CPL), to light in an isotropic medium, where the optical chirality is not well defined. We find the generalized optimal chirality condition by enforcing the constructive scattering of the chiral response of chiral molecules with the phase shift between the incident electric and magnetic fields. The generalized OCL displays powerful electric-magnetic symmetries that maximize chiral light-matter interactions with simplified expressions.

We first perform numerical simulations of the near-field optical chirality around the nanostructures and show how the local chiro-optical effects around symmetric and asymmetric plasmonic and plasmonic-dielectric nanostructures can be tailored. In particular, we study simple geometries based on plasmonic nanohole arrays or nanowires or nanospheres asymmetrically covered by metal. Then, we study the influence of the nanoscale effects the overall macroscopic chiro-optical response that we can measure in various ways. We first conventionally measure extrinsic chirality by shining a widely tunable laser on the sample and measuring polarization-dependent transmission or reflection, which depends on the sample’s orientation and the incidence angle. We also study asymmetric metasurfaces by photothermal techniques: photo-acoustic and photo-deflection techniques, to measure scattering-free absorption and diffraction effects, respectively. Finally, we reveal how the plasmonic asymmetry influences the polarization states of the transmitted light (spectral and incidence angle dependence).

Optical bottle beams (OBBs) are beams of light where a dark region is completely surrounded by light, but so far, this is not always the case. In modern OBBs, created by Bessel and vortex beams, nodal surfaces are present leading to a three-dimensional lobed structure in coherent beams. But is this always the case? We use a combination of computational modeling with novel phase retrieval techniques and polarization-dependent wavefront shaping to explore the creation of computer-generated holographic bottle beams. We discuss the creation of such beams, and how to maintain a “perfect bottle”.

This presentation demonstrates the creation and characterization of a family of structured light referred to as meronic beams. The topological structures of merons (half-skyrmions) and their higher order variants are characterized, and we show how meronic beams can be generated using gradient index lens cascades. This also includes the generation of quadrumeron and quadrumeronium beams as well as more complex light fields with high beam quality. Finally, we show how meron beams of arbitrary order can be generated using spatial light modulators and can be subsequently reconfigured to demonstrate tuning of the beam profile.

We show that the photonic spin distribution of a monochromatic electromagnetic field in the three-dimensional real space may form a hopfion texture. The topological property of such distribution is characterized by the integer-valued Hopf charges. We show that photonic spin texture of arbitrary Hopf charges may be created. When extending the distribution to four dimensions by introducing a parameter dimension, a monopole loop defect carrying quantized Hopf charge is encountered. Such photonic spin texture and defect may find application in control and sensing of nanoparticles, and optical generation of topological texture in the motion of particles or fluids.

As artificial intelligence (AI) use grows, the demand for computing resources has increased dramatically. Server costs are significant and highlight the need for more energy-efficient and cost-effective computing platforms for AI applications and future growth. One potential solution is optical hardware. Optical computing hardware has several advantages, such as high bandwidth parallelism and energy efficiency. However, one major limitation is the implementation of nonlinear calculations in the optical domain. We will discuss an approach that achieves the equivalent of optical nonlinearity vastly more effectively than current approaches. The essence of the technique relies on multiple linear scattering off data encoded onto a spatial light modulator (SLM) that uses low optical power to effectively synthesise a nonlinear operation. By exploiting this relationship, arbitrary nonlinear transformations are programmed digitally, and light effectively performs an all-optical computation without requiring electronic switching or high peak power to achieve non-linearity.

The efficient conversion of light from a multimode to a single mode optical fiber is an area of active research for applications such as telecommunications, astronomy, and high-power lasers. In this work, we demonstrate the ability to wavefront shape the input to a multimode fibre and achieve high efficiency coupling into a physically connected single mode fibre output. That is, without intermediate free space optics. The wavefront shaping creates a focused diffraction limited spot at the multimode fiber output, which is coupled to the core of the single mode fiber. Light that is not coupled to the single mode fiber core is coupled to the cladding and stripped. We have achieved up to 40% coupling with near diffraction limited output using phase only modulation.

We study the far-field patterns and the near-field evolution in free space of arrays of N x M point-vortices with equal unitary topological charge embedded in carrier beams with different geometries as a function of different control parameters. Particularly, we analyze the case of elliptical Gaussian beams with different eccentricity and a plane wave diffracted by a rectangular aperture. We identify a geometrical parameter characterizing the size of the lattice with respect to the size of the carrier in each direction, which ultimately determines the far-field pattern and the final configuration of the vortices, which exhibits structure transitions under some conditions. In the near field, we find an expression for the rotation angle of the whole structure, while preserved, as a function of the propagation distance, which depends on the separation distance between adjacent vortices in each direction. Our numerical results are verified with experiments, showing an excellent agreement.