Experimental generation of scalar and vector vortex Pearcey-Gauss beamsRodríguez-Fajardo, Valeria; Flores-Cova, Gabriela; Rosales-Guzmán, Carmelo; Perez-Garcia, Benjamin
doi: 10.1117/12.3057019pmid: N/A
In this work, two new types of structured light beams are introduced: the vortex Pearcey-Gauss (VPeG) beam, with homogeneous polarization, and the vector vortex Pearcey-Gauss (VVPeG) beam, featuring non-homogeneous, non-separable polarization. Scalar Pearcey-Gauss beams were generated using a spatial light modulator, while vortex and vector vortex beams were created using a q-plate with circular and linear polarization, respectively. Their intensity and polarization evolution along propagation were characterized using Stokes polarimetry and compared with simulations. The VVPeG beam transforms from linear to near full-Poincaré polarization, enriching the family of non-separable states with promising applications in optical metrology and tweezers.
Multipolar electromagnetic radiationMansuripur, Masud; Jakobsen, Per Kristen
doi: 10.1117/12.3064146pmid: N/A
An oscillating electric dipole, localized at the origin of coordinates and represented by a three-dimensional delta-function in the xyz-space, radiates a classical electromagnetic (EM) field into its surrounding free space at its oscillation frequency ω. Combinations of delta-functions and their various derivatives with respect to x, y, and z can be similarly used to model electric as well as magnetic multipole radiators. We examine the emitted EM energy and angular momentum for several multipoles modeled by such localized oscillators. A quantum interpretation of these classical results can be loosely related to photoemission processes involving transitions between various electronic states of an atom or a molecule.
Proposal of dynamic response sampling method for 6DoF control of irregularly shaped micro-scale objects with optical tweezersOmine, R.; Masui, S.; Michihata, M.; Takahashi, S.
doi: 10.1117/12.3063257pmid: N/A
3D position and orientation control (6DoF control) of micro-scale objects is needed among diverse applications such as cell manipulation, micro-assembly, and analysis of environmental microparticles. While optical tweezers technique is a promising tool for micro-manipulation including rotational control, the majority of previous studies depend on a priori knowledge on object shapes, which limits their applicability to real tasks where object shapes are usually irregular and not predetermined. To overcome this, we have proposed a concept of real-time adaptive optical tweezers, which generates illumination patterns of optical tweezers in real time based on acquired real-time information about objective particles. In this paper, as a new method which realizes real-time adaptive optical tweezers, we propose what we call Dynamic Response Sampling Method (DRSM). This method consists of two steps. Firstly, in the sampling step, illumination with randomly generated patterns and recording of instant 6DoF motion (i.e. velocity and angular velocity) are conducted. Secondly, a set of non-negative coefficients of superposition of the illumination patterns which realize desired 6DoF motion are calculated using algorithms such as the non-negative least squares method, then 6DoF control is realized using this superposed illumination pattern. We demonstrated this method in simulation and experiments. First, we confirmed that desired velocity and angular velocity are applied to Gaussian random ellipsoids (a model of irregularly shaped particles) with ray-optics based simulation. In addition, we successfully applied desired velocity to rounded L-shape resin microparticles (~20 μm) and irregularly shaped polystyrene microparticles (~50μm) in experiments.
Optical waveguides deformed by guided lightBánó, Gregor; Iványi, Gergely T.; Slabý, Cyril; Kubacková, Jana; Strejčková, Alena; Jurašeková, Zuzana; Tomori, Zoltán; Hovan, Andrej; Kelemen, Lóránd; Vizsnyiczai, Gaszton
doi: 10.1117/12.3065749pmid: N/A
Optical forces emerge when light travels through curved waveguides. This study presents experimental evidence that optical forces can cause significant mechanical deformation in micron-scaled curved optical waveguides made of a soft polymer material. The findings are further supported by an analytical model that considers the mechanical properties of the photopolymer waveguide.
Holographic optical tweezers for rotational control of self-assembled nanodiamondStewart, Adam; El-Helou, Anthony J.; Reece, Peter J.
doi: 10.1117/12.3060607pmid: N/A
Here we conduct a study of optical torques exerted by focused Laguerre-Gaussian (LG) modes on nanodiamond (ND) geometries in holographic optical tweezers (HOT). We model the interaction between structured light fields and self-assembled ND geometries, comparing nanodiamond and polystyrene materials. We find that ND particles in LG beam carrying orbital angular momentum (OAM) experience high axial torque that can drive rotations. These findings support the use of optically driven LG beam modes for alignment of nitrogen vacancy (NV) defect centers in ND crystals, where control over NV orientation is an important factor in quantum vector magnetometer experiments.
Taking advantage of the polarization-dependent light-driven dynamics of gold nanorodsRodrigo, José A.; Alieva, Tatiana
doi: 10.1117/12.3063912pmid: N/A
We introduce a multifunctional experimental setup and technique based on holographic curve-shaped laser traps to analyze the dynamics of light-driven colloidal gold nanorods (GNRs). The experimental results, supported by theoretical models and numerical simulations, demonstrate that the transport speed of GNRs along a designed trajectory is influenced by the polarization of light under constant laser power. Specifically, for the considered GNR, the speed was more than twice as fast under linear polarization compared to circular polarization. Moreover, the speed depends on the particle’s orientation. When the GNR is aligned with the propulsion direction, its speed is significantly greater than when it is oriented perpendicular to the propagation direction. The dependence of speed on asymmetric particle orientation arises from the interplay between optical and hydrodynamic forces acting on the particle. Furthermore, our study reveals that the dynamics of GNRs in structured traps and their spinning within point-like traps are significantly influenced by particle size and aspect ratio. Despite small statistical fluctuations in particle sizes according to the manufacturer, differences in spinning frequency and translational speed of GNRs from the same set can be effectively quantified, paving the way for dynamic single-particle characterization.
A comparison of nitrogen vacancy centre defect fluorescence characteristics in optically trapped nanodiamondsReece, Peter J.; Goh, Jin Tong; Stewart, Adam
doi: 10.1117/12.3066226pmid: N/A
Bright fluorescent nanodiamonds (NDs) that are suitable for combined optical trapping and magnetic resonance sensing experiments are typically prepared from high pressure high temperature (HPHT) diamond. The nature of the synthesis method yields a poly-dispersion of sizes and shapes, and with a range of optoelectronic properties that may be more or less suitable for magnetic resonance sensing. In this paper we explore the possibility of using trapping metrics and fluorescence properties as a proxy for identifying NDs with strong optically detected magnetic resonance (ODMR) contrast. Our results suggest that larger NDs, characterized by a strong fluorescence count and high trap stiffness typically yield more favourable ODMR contrast.
Synchronised motion of gold nanoparticles in a surfactant-assisted optothermal trapShukla, Ashutosh; Chand, Rahul; Boby, Sneha; Kumar, G. V. Pavan
doi: 10.1117/12.3063673pmid: N/A
Surfactants, commonly used to stabilise colloidal suspensions, notably affect the optical trapping of particles. This study focuses on opto-thermal trapping of gold nanoparticles in a surfactant solution, specifically Cetyltrimethylammomium chloride. By creating an optothermal trap with a single drop-casted gold particle at nominal powers, we observed that other particles are trapped at a radial position between 1 and 2 μm. When multiple particles are trapped, their diffusive motion around the centre particle is synchronised. We explore the phenomenon through simulated forces, probing how surfactants influence particle behaviour in optical trapping systems. We further study this trapping behaviour by variations of surfactant concentration, laser power and laser polarisation. We also checked the effect in the presence of different surfactants.
Trapping and chemical characterization of sub-microplastics using Raman optical tweezers with machine learningLu, Yuli; Toulkeridou, Evropi; Zheng, Changcheng; Kotsifaki, Domna G.
doi: 10.1117/12.3062593pmid: N/A
The accumulation of plastics in the environment and their fragmentation into micro- and nanoplastics represent a growing ecological and public health concern. Accurate detection and classification of these particles remain challenging due to their small size and the complexity of environmental matrices. Here, we present an advanced analytical platform that combines optical tweezers Raman spectroscopy (OTRS) with machine learning-driven principal component analysis (PCA) to enable precise identification of microplastics at the single-particle level. By analyzing 35 Raman spectra, we demonstrate the platform’s ability to effectively distinguish common plastics—such as polyethylene (PE), polypropylene (PP), and polystyrene (PS)—from organic matter without extensive sample preparation. This approach not only enhances sensitivity and specificity but also supports high-throughput, automated analysis, offering a scalable solution for real-time environmental monitoring. Our findings highlight the potential of this integrated method to improve microplastic surveillance and inform mitigation strategies in polluted ecosystems.