Optical trapping is a non-invasive technique for manipulating nano- and microscopic objects and is widely used to investigate biological processes, such as membrane viscosity, membrane-cytoskeleton interactions, and the regulation of cellular functions. Optical vortex beams can maintain orbital angular momentum (OAM) and have recently been used for optical manipulation. When nanoparticles in aqueous solutions are rotated at the laser focus owing to the optical forces derived from the optical vortex beam, their subsequent motion is governed by the OAM. The dynamics of nanoparticles attached to the biological membrane may be further affected by the viscoelasticity of the membrane and hydrodynamic coupling; however, it is unclear whether such rotational motion on lipid bilayers can be controlled. In this study, we applied an optical vortex beam to the two-dimensional rotational manipulation of fluorescent nanoparticles attached to a supporting lipid bilayer (SLB) and investigated their rotational behavior. We revealed that the single nanoparticles attached to the SLB rotated more slowly than those in an aqueous solution, but their orbital motion was still clearly driven by the OAM of the beam. The orbital radius of rotation was tuned according to the magnitude of the topological charge, and an angle velocity that changed linearly in proportion to both the laser power and nanoparticle diffusion coefficient was identified, which was consistent with theoretical calculations. These results suggest that optical vortex beams can manipulate nanoparticles attached to SLB with controllable rotational dynamics. Such rotational manipulation of nanoparticles on lipid bilayers can provide a platform for studying the effects of nanoparticle rotation on the local organization of membrane components and can be useful for developing methods to regulate their dynamic properties.

Optical beams with spatially variant coherence properties from an unpolarized laser

Propagation of perfect optical vortex beams in a strongly nonlocal nonlinear medium

All-in-one laser self-mixing prototype for optical power and beam size measurement using back-scattered light

Beam optics analysis and preliminary results of 120 keV multi-slit accelerator prototype for neutral beam injector

Based on the birefringence phenomenon of vortex beam in uniaxial crystals for optical path design, yttrium vanadate crystals and waveplates are used to realize coherent mixing of vortex beam. A crystal-type spatial light mixer applied to a vortex beam communication system is designed. The effects of beam polarization, waveplate optical axis, crystal transmittance, and other factors on the performance of the mixer are explored. Simulations show that the mixer output phase error is extremely small, the insertion loss is about 1.9 dB , and the overall loss is close to 36.6%. Finally, it is applied in the vortex optical coherent communication system, and the effectiveness of the optical mixer is experimentally verified with a phase deviation of 3°, a splitting ratio close to 1, and a mixing efficiency of 78.5%. Vortex beam mixer extracts information such as phase, amplitude, and polarization of the signal light by combining optical beams with orbital angular momentum modes. It enables mode multiplexing, topologically protected transmission, and high-order modulation. This technology is widely applied in space optical communication, high-speed fiber-optic systems, and quantum communication.

The formation of optical solitons in nonlinear media is governed by the balance among diffraction effects, potential well confinement, and nonlinear effect interactions, a dynamic process that is critically determined by the configuration of the potential well. The results demonstrate that adjusting the spatial arrangement of the potential well enables precise control over the structural shaping of the optical beam. The introduction of a rotational structure within the potential well can induce rotational dynamics in the optical field. The gradual change potential well structure supports the stable morphological transformation of solitons, accommodating isotropic and anisotropic modulation. These findings provide a theoretical foundation for potential applications in advanced optical technologies, such as beam shaping and optical signal processing.

Abstract An audio coding method based on multi-ring optical perfect vortex beam (MR-OPVB) is proposed, which uses its orbital angular momentum (OAM) as the information carrier, and realizes efficient signal coding through MR-OPVB. The coaxial interference method of fundamental-mode Gaussian beams was used to extract OAM information, focusing on the interference effects between perfect vortex waves of different radii and their impact on OAM recognition, as well as strategies to mitigate such interference disturbances. Convolutional neural network was used to recognize the mode of MR-OPVB affected by atmospheric turbulence, which can achieve 99.8% recognition accuracy in moderate turbulence conditions. The trained resnet-18 model was utilized to identify and decode the MR-OPVB affected by atmospheric turbulence, and the distortion rate of the recovered audio signal was 0.954%. This study offers a coding concept for optical perfect vortex beam communication and validates that machine learning can effectively enhance the quality of free space optical communication.

ABSTRACT Optical vortex beams, carrying orbital angular momentum (OAM), are of great interest for applications in optical communications, particle manipulation, and quantum information processing. However, achieving high‐efficiency generation and manipulation of vortex beams with a single compact element, particularly in the visible range, remains challenging. Here, we demonstrate laser‐written geometric phase fork gratings in silica glass that enable simultaneous generation and propagation control of vortex beams with an efficiency up to 98.4% at 515 nm. By tailoring the phase‐gradient period and topological charge ( l = 1–100), we achieve tunable control over the vortex beam's topological charge, diameter, and diffraction position. The fabricated gratings maintain high efficiency across a broad spectral range from 450 to 690 nm. Furthermore, we demonstrate spin–orbit coupling between incident vortices and fork gratings, verifying that the output OAM values follow the expected addition rule l out = l in ± l fork . In addition, the fork gratings exhibit excellent thermal stability (up to 800°C) and optical damage threshold (close to pristine silica glass). These results establish nanopore‐based geometric‐phase fork gratings as a scalable, broadband, high‐performance platform with outstanding thermal and optical tolerance for next‐generation OAM photonics.

Angular dependence of low divergence optical beams propagated in the marine atmospheric surface layer

Peripapillary choroidal melanoma provides a unique challenge; proximity to visually important structures, such as the optic disc and fovea, confers a high risk for the development of maculopathy and optic neuropathy, leading to poorer visual outcomes with most forms of radiotherapy. Ocular proton therapy (OPT) requires an aperture to shape the beam to the tumour. An aperture 'notch' may minimise damage to the optic disc and/or the fovea. This study aims to explore if there are any additional advantages to incorporating a notch over the optic nerve beam area. Retrospective audit (cohort study). Participants included eighty-three patients treated at Liverpool with proton beam therapy from January 2012 to March 2020 for their peripapillary choroidal melanoma. All had a minimum of two and a half years of follow-up vision data; this was to ensure there was enough visual acuity assessment data to perform sufficient analysis. Patients excluded had choroidal melanoma situated over 3 mm from the optic disc, as these were unlikely to have an aperture notch. A retrospective audit was undertaken in accordance with the Declaration of Helsinki, and registered with the Royal Liverpool Hospitals audit department (audit reference number: Ophth/SE/2024-25/25). Data was collated from the Liverpool Ocular Oncology database, clinic letters and the individual proton beam 3D plans. Robust statistical analysis using a mixed effects model was used to explore associations between notched beams and vision loss and complications. The primary outcome measure is visual acuity loss post-proton beam therapy. Secondary outcome measures were enucleation and other complication rates. Analysis shows that at 10 years post-OPT, there would be an expected 0.058 (p = 0.077) logMAR of vision saved using a notch for the optic disc compared to no notch (normal apertures); this is considered clinically significant. This cohort also loses vision at a slower rate than other cases. No other predictors were found to be statistically significant for loss of vision, and notched beams showed no advantage in reducing rates of complications. There is some evidence of a trend that utilising a notch for optic disc does show long-term vision benefit; it demonstrates a clinically significant benefit in patients with peripapillary choroidal melanoma.

On-chip laterally confined GHz acoustic modes with tunable helicity open the way for advanced optomechanical functionalities. Here, we demonstrate a novel concept for the electrical generation of GHz membrane-like helical drum modes on a chip, and propose their application to the future generation of optical beams with tunable orbital angular momentum (OAM). Our concept relies on the strong dependence of the frequency spectrum of Lamb-like acoustic modes on the thickness of the propagating medium. Modes generated by a piezoelectric resonator in a thicker (or thinner) substrate region remain confined in this region via reflections at the lateral boundaries with thinner (thicker) substrate regions. If the generation region is disk-shaped, the lateral reflections form drum-like modes, which we experimentally confirm with radio-frequency spectroscopy and interferometric maps of the surface displacements. Furthermore, we show that an array of sector-shaped piezoelectric transducers powered with appropriate radio-frequency phases creates acoustic vortices with tunable OAM polarity, which we transfer to an optical beam. Our analytical and finite-element models yield useful insights into the acoustic coupling of bulk and surface modes that can guide adaptation to other material systems. These acoustic drum modes provide a flexible platform for acousto-optical chiral functionalities in the GHz frequency range.

Abstract Features of complex vector light become important in any interference effects, including scattering, diffraction, and nonlinear processes. Here, we are investigating the role of polarization-structured light in atomic state interferometers. Unlike optical or atomic path interferometers, these facilitate local interference between atomic transition amplitudes and hence the orthogonal optical polarization components driving these transitions. We develop a fully analytical description for the interaction of generalized structured light with an atomic four state system, that is, multiply connected via optical as well as magnetic transitions. Our model allows us to identify spatially dependent dark states, associated with spatially structured absorption coefficients, which are defined by the geometry of the polarization state and the magnetic field direction. We illustrate this for a range of optical beams including polarization vortices, optical skyrmions, and polarization lattices. This results in a new interpretation and an enhanced understanding of atomic state interferometry, and a versatile mechanism to modify and control optical absorption as a function of polarization and magnetic field alignment.

As a paraxial wave packet is reflected or refracted from a planar interface separating two material media, it experiences spatial and angular shifts of its center position with respect to predictions of the geometrical ray picture. These in-plane and out-of-plane beam shifts are known as Goos-Hänchen and Imbert-Fedorov shifts, respectively. We discover a universal link between the phase-space nonseparability of an incident wave packet of any degree of spatial coherence and the reflected beam shifts. We unveil coherence Goos-Hänchen and coherence Hall effects, absent in the fully coherent limit. While the former effect can trigger a pronounced enhancement of the spatial Goos-Hänchen shift, the latter enables control of the spatial Imbert-Fedorov shift, from complete cancellation at a certain incidence angle to dramatic enhancement of the shift to giant magnitudes for nearly incoherent incident wave packets. Our results are equally applicable to optical, x-ray, and neutron, as well as matter waves, and they showcase novel phenomena in wave-matter interactions.

Scaling acoustic vortex traps with topological charge.

Dynamic optical beam steering characteristics based on cascaded liquid crystal polarization gratings

Optimization of the Launched Optical Beam Profile for High-Speed Avalanche Photodiodes to Enhance the Wide Dynamic Range Performance

We present the design of a microbeam system as a major utilization of the planned K100 MeV compact cyclotron dedicated to accelerating Q/A = 1/2 ions. The maximum beam energy is 25 MeV/u, which can be considered suitable for high-energy microprobing, and a microbeam is formed by quadrupole focusing. Both vertical and horizontal microbeam lines are employed to comfortably accommodate living cells and chips as targets, respectively. Linear beam optics simulation is performed to achieve a demagnification factor of over 10 while high-order optics are being evaluated to minimize optical aberrations. In the vertical beam line, the slits are placed at two peak dispersive locations to reduce the beam-size spreads caused by momentum dispersion of the cyclotron beam. The particle tracking code TURTLE is used to calculate dispersion effects including the slits and non-linear fields of the quadrupole and dipole magnets. Finally, an initial design of the vertical target chamber is carried out to evaluate the requirements of radiobiology users such as handling of a large number of samples in a short time.

The EuPRAXIA project [Walker et al., J. Phys.: Conf. Ser. 874, 012029 (2017)] aims to construct two state-of-the-art accelerator facilities based on plasma accelerator technology. Plasma-based accelerators offer the possibility of a significant reduction in facility size and cost savings over current radio frequency (RF) accelerators. The two facilities—one laser-driven, one a beam-driven—are envisioned to provide electron beams with an energy in the range of 1–5 GeV and beam quality comparable to existing RF machines. This will enable a versatile portfolio of applications from compact free-electron laser drivers to sources for medical and industrial imaging. At the heart of both facilities is the use of plasma-based accelerator components and systems, which encompass not only the accelerating medium itself but also a range of auxiliary systems such as plasma-based electron beam optics and plasma-based mirrors for high-intensity lasers. From a technical standpoint, a high-degree of control over these plasma devices will be essential for EuPRAXIA to achieve its target performance goals. The ability to diagnose and characterize these plasma devices and to simulate their operation will be further essential success factors. Additionally, compatibility with extended operation at high-repetition rates and integration into the accelerator beamline will also prove crucial. In this work, we aim to review the current status of plasma components and related systems for both laser-driven and beam-driven plasma accelerators and to assess challenges to be addressed regarding implementation at future EuPRAXIA facilities.

We report the development of an instrument combining an ultrafast, high-repetition-rate, polarization-tunable monochromatic extreme ultraviolet (XUV, 21.6eV) beamline and a next-generation momentum microscope end station. This setup enables time- and angle-resolved photoemission spectroscopy of quantum materials, offering multimodal photoemission dichroism capabilities. The momentum microscope simultaneously detects the full surface Brillouin zone over an extended binding energy range. It is equipped with advanced electron optics, including a new type of front lens that supports multiple operational modes. Enhanced spatial resolution is achieved by combining the small XUV beam footprint (33 × 45μm2) with the selection of small regions of interest using apertures positioned in the Gaussian plane of the momentum microscope. This instrument achieves an energy resolution of 44meV and a temporal resolution of 144fs. We demonstrate the capability to perform linear, Fourier, and circular dichroism in photoelectron angular distributions from photoexcited 2D materials. This functionality paves the way for time-, energy-, and momentum-resolved investigations of orbital and quantum geometrical properties underlying the electronic structures of quantum materials driven out of equilibrium.