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The invention of optical tweezers almost forty years ago has triggered applications spanning multiple disciplines and has also found its way into commercial products. A major breakthrough came with the invention of holographic optical tweezers (HOTs), allowing simultaneous manipulation of many particles, traditionally done with arrays of scalar beams. Here we demonstrate a vector HOT with arrays of digitally controlled Higher-Order Poincaré Sphere (HOPS) beams. We employ a simple set-up using a spatial light modulator and show that each beam in the array can be manipulated independently and set to an arbitrary HOPS state, including replicating traditional scalar beam HOTs. We demonstrate trapping and tweezing with customized arrays of HOPS beams comprising scalar orbital angular momentum and cylindrical vector beams, including radially and azimuthally polarized beams simultaneously in the same trap. Our approach is general enough to be easily extended to arbitrary vector beams, could be implemented with fast refresh rates and will be of interest to the structured light and optical manipulation communities alike. [ABSTRACT FROM AUTHOR]

Circular Airy Gaussian vortex (CAGV) beams have gained great popularity in areas of research such as optical tweezers and optical communications due to their fascinating properties, such as auto-focusing and self-healing. The propagation dynamics of these beams is dictated by their topological charge and launch angle. For example, larger topological charges and positive launch angles enhance the maximum intensity in the focal plane while simultaneously shortening the focal length of autofocusing. Crucially, while the generation of single CAGV beams has been widely reported, the simultaneous generation of multiple CAGV beams, has remained challenging. Here, we put forward a novel technique that enables the simultaneous generation of multiple CAGV beams with independent topological charges or initial launch angles from a single digital hologram encoded on a spatial light modulator (SLM). Our technique enables the independent manipulation of each CAGV beam, their topological charge and launch angle, at refresh rates limited only by the SLM (60 Hz). This technique paves the way for the simultaneous manipulation of microparticles in three dimensions and provides with an alternative way to realize optical communications with multiple spatial modes of light. [ABSTRACT FROM AUTHOR]

The on-demand tailoring of light's spatial shape is of great relevance in a wide variety of research areas. Computer-controlled devices, such as spatial light modulators (SLMs) or digital micromirror devices, offer a very accurate, flexible and fast holographic means to this end. Remarkably, digital holography affords the simultaneous generation of multiple beams (multiplexing), a tool with numerous applications in many fields. Here, we provide a self-contained tutorial on light beam multiplexing. Through the use of several examples, the readers will be guided step by step in the process of light beam shaping and multiplexing. Additionally, we provide a quantitative analysis on the multiplexing capabilities of SLMs to assess the maximum number of beams that can be multiplexed on a single SLM, showing approximately 200 modes on a single hologram. [ABSTRACT FROM AUTHOR]

Complex vector light modes, characterized by a non-uniform transverse polarization distribution, have pervaded a wide range of research fields. In this study, we propose an approach that enables the simultaneous generation of multiple vector beams based on a spatially segmented digital hologram and two or more cascaded beam displacers. More precisely, an input beam is separated into multiple parallel copies spatially separated, which are then sent to the center of each segmented hologram, enabling independent modulation of each beam. The modulated beams are then judiciously recombined with a beam displacer to generate multiple vector modes in a simultaneous way. We demonstrated our technique with two arbitrary vector modes but the technique can be easily extended to more by inserting additional beam displacers. To assess the quality of the generated vector modes, we employed Stokes polarimetry to reconstruct their transverse polarization distribution and to measure their degree of non-separability. We envision that this technique will find significant applications in various fields, including optical communications, optical sensing, and optical tweezers to mention a few. [ABSTRACT FROM AUTHOR]

Vector beams display varying polarisation over planes transversal to their direction of propagation. The variation of polarisation implies that the electric field cannot be expressed as a product of a spatial mode and its polarisation. This non-separability has been analysed for particular vector beams in terms of non–quantum entanglement between the spatial and the polarisation-degrees of freedom, and equivalently, with respect to the degree of polarisation of light. Here we demonstrate theoretically and experimentally that Mathieu–Gauss vector modes violate a Bell-like inequality known as the Clauser–Horn–Shimony–Holt–Bell inequality. This demonstration provides new insights on the violation of Bell inequalities by a more general class of vector modes with elliptical symmetry. [ABSTRACT FROM AUTHOR]

Complex vector modes represent a general state of light nonseparable in their spatial and polarization degrees of freedom, which have inspired a wide variety of novel applications and phenomena, such as their unexpected propagation behaviour. For example, they can propagate describing periodic polarization transitions, changing from one vector beam to another. Here, we put forward a novel class of vector modes with the capability to experience an abruptly autofocusing behaviour. To achieve such beams, we encode the spatial degree of freedom in the Circular Airy Gaussian vortex (CAGV) beams. We demonstrate the experimental generation of arbitrary CAGV vector beams and evince some of their properties, such as a rotation of intermodal phase. We anticipate that the fascinating properties of theses modes will prompt the development of novel applications associated to their autofocusing behaviour and polarization distribution. [ABSTRACT FROM AUTHOR]

Autocorrelation measurement based on second-harmonic generation (SHG), the best-known technique for measuring the temporal duration of ultrashort pulses, dates back to the birth of ultrafast lasers. Here, it is proposed and experimentally demonstrated that such well-established technique can be used to measure the orbital angular momentum of ultrashort Laguerre–Gauss (LG) pulses. By analyzing the spatial spectrum (i.e., the far-field pattern) of the SHG signal with a spatially-resolved detector, the full spatial structure of ultrashort LG pulses, including both azimuthal and radial indices, are unambiguously determined. The results provide an important advancement for the well-established autocorrelation technique by extending it to reach its full potential in laser characterization, especially for structured ultrashort pulses. [ABSTRACT FROM AUTHOR]

• Kinetics of RAFT (co)polymerization of pentafluorophenyl (meth)acrylate are reported. • An automated parallel synthesizer facilitated the generation of experimental data. • Control using a dithiobenzoate for acrylate polymerization depended on the solvent. • Control for methacrylate copolymerizations depended on initial comonomer composition. Pentafluorophenyl methacrylate (PFPMA) and pentafluorophenyl acrylate (PFPA) are frequently used monomers to produce advanced materials for biomedical applications via (co)polymerization reactions. This contribution reports kinetic investigations of the reversible addition fragmentation chain transfer (RAFT) copolymerization of PFPMA and methyl methacrylate (MMA) mediated by a dithiobenzoate chain transfer agent (CTA) at 70 °C in dimethyl formamide (DMF). Control with respect to the molar mass of the copolymers was observed for initial PFPMA monomer feeds ≤40 mol%. The rate of PFPMA incorporation decreased with increasing initial PFPMA feed ratios. Reactivity ratios were estimated with a nonlinear regression that utilizes a visualization of the sum of squares space method (r PFPMA = 1.06 and r MMA = 0.44). The slight preference for MMA-type radicals to add PFPMA monomers increased the rate of consumption of PFPMA especially in low initial PFPMA monomer feeds. In addition, kinetic investigations of the RAFT homopolymerization of PFPA revealed an induction period and poor control on the polymer molar mass in the polar solvents acetonitrile and DMF using a dithiobenzoate CTA. A better control using the same CTA was observed in 1,4-dioxane. Polymerizations carried out in the presence of a trithiocarbonate CTA were less affected by the solvent polarity and a good control on the polymer molar mass was achieved in acetonitrile and 1,4-dioxane even at high monomer conversion (>95%, dispersity value (Ð) ≤ 1.19). [ABSTRACT FROM AUTHOR]

• Quaternized monomer is polymerized into tailored thermoresponsive quasi -block copolymers. • Obtained quasi -block copolymers show thermo-induced self-assembly in aqueous solutions. • Thermal transitions are tuned as a function of M n , composition of quaternized monomer and temperature. • Quaternized cationic sites favor the formation of metastable nanostructures. • A material which is practically an homopolymer can show self-assembly properties. We describe the sequential incorporation of the quaternized monomer N -(2-(Methacryloyloxy)ethyl)- N,N -dimethylheptan-1-ammonium (QDM) (from 1 up to 5 mol %) into 2-((dimethylamino)ethyl methacrylate) polymer chains (PDMAEMA), via reversible addition-fragmentation chain transfer (RAFT) technique, to yield quasi -block copolymers (PDMAEMA- qb -P(DMAEMA- co -QDM)) with modified hydrophilic nature and thermo-induced self-assembly properties in aqueous solutions. This chemical modification promotes the formation of metastable nanostructures in aqueous medium. The morphological transitions were investigated by means of atomic force microscopy (AFM), dynamic light scattering (DLS), rheology and turbidimetry. The results indicated that the obtained nanostructures were stabilized by associative and cationic interactions conveyed by the quaternized moieties within the polymer chains. The size of these nanostructures could be modified as a function of molar mass, copolymer composition and temperature. The method described denotes an interesting alternative to modify the thermo-induced self-assembly behavior of PDMAEMA based copolymers employing low amounts of quaternized moieties. [ABSTRACT FROM AUTHOR]

It is well known that when a laser is reflected from a rough surface or transmitted through a diffusive medium, a speckle pattern will be formed at a given observation plane. An important parameter of speckle is its size, which for the case of homogeneous illumination, well-known relations for its computation have been derived. This is not the case for structured light beams of non-homogeneous intensity and phase distribution. Here, we propose and demonstrate, using Hermite- and Laguerre-Gaussian light modes, that the mean size of the speckle generated by these structured light beams can be measured assuming a homogeneous illumination. We further provide with mathematical expressions that relate the speckle size to the generalised definition of "spot size". To reinforce our assessment, we compare the mean speckle size generated by structured light modes with that generated by wave fronts of constant phase and amplitude and show that in both cases the mean speckle size is almost identical. Our findings reveal a fundamental property of speckle, which will be of great relevance in many speckle-based applications and will pave the way towards the development of novel applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • GMMA was copolymerized with NHSMA, NIPAM, and BuA. • Reactivity ratios of GMMA-based copolymers were calculated by Mayo-Lewis equation. • Glass transition temperatures were estimated by Fox, Brostow and Kwei equations, and compared to experimental measurements. • Cloud point temperatures of aqueous solutions were evaluated by turbidimetry. • Cell viability of thermoresponsive copolymers were analyzed for the L929 cell line. Understanding the chemical composition of biocompatible copolymers is crucial for diverse biomedical applications such as the conjugation of polymers to drugs, peptides or proteins. Here, we report the Reversible Addition-Fragmentation Chain Transfer (RAFT) copolymerizations and reactivity ratios (r) of the less explored biocompatible copolymer systems based on glycerol mono-methacrylate (GMMA) monomer. Hence, we investigated the copolymerization of GMMA with the comonomers N-hydroxy succinimide methacrylate (NHSMA), N-isopropylacrylamide (NIPAM) and butyl acrylate (BuA). The estimated r values and sequence length distributions suggest that a chain radical of GMMA monomer prefers cross propagation in the system GMMA/NHSMA (r GMMA = 0.32 r NHSMA = 1.01). In the case of GMMA/NIPAM (r GMMA = 2.55 r NIPAM = 0.11) and GMMA/BuA (r GMMA = 3.31 r BuA = 0.66) systems, as shown by the relatively high r GMMA values in both copolymerizations, the formation of gradient copolymers might be favored. To understand the role of the comonomer composition in the thermal and solution properties of the final materials, the glass transition temperature (T g) values of the copolymers, as determined by differential scanning calorimetry (DSC), were compared to build T g vs. composition plots generated with the Fox, Brostow and Kwei equations. DSC investigations also revealed an interesting effect of molecular interactions between the polymer chains possibly formed via hydrogen bonding conveyed by the GMMA groups in the copolymers. Furthermore, light transmittance measurements of the poly(GMMA- stat -NIPAM) copolymer system in aqueous solutions revealed that the cloud point temperature (T cp) of the solutions increases with the content of GMMA groups in the copolymer; however, this behavior was limited by the NIPAM composition (>0.74 mol fraction). Interestingly, a copolymer material with a GMMA/NIPAM composition (F GMMA /F NIPAM) of 26/74 exhibited a T CP = 38 °C, which is close to the human body temperature. Finally, cytotoxicity assays indicated the excellent biocompatibility of the obtained copolymers, which suggests that these copolymer systems might be suitable alternatives for bioconjugated systems in biomedical applications. [ABSTRACT FROM AUTHOR]