Applications In Optical Manipulation Research Articles

Switchable hybrid-order optical vortex lattice.

Optical vortex (OV) modulation is a powerful technique for enhancing the intrinsic degrees-of-freedom in structured light applications. Particularly, the lattices involving multiple OVs have garnered significant academic interest owing to their wide applicability in optical tweezers and condensed matter physics. However, all OVs in a lattice possess the same order, which cannot be modulated individually, limiting its versatile application. Herein, we propose, to our knowledge, a novel concept, called the hot-swap method, to design a switchable hybrid-order OV lattice, in which each OV is easily replaced by arbitrary orders. We experimentally generated the switchable hybrid-order OV lattice and studied its characteristics, including interferograms, retrieved phase, energy flow, and orbital angular momentum. Furthermore, the significant advantages of the switchable hybrid-order OV lattice are demonstrated through the independent manipulation of multiple yeast cells. This study provides a novel scheme for accurate control and modulation of OV lattices, which greatly facilitates the diverse applications of optical manipulation and particle trapping and control.

Generalized Lorenz-Mie theory and simulation software for structured light scattering by particles

Structured light refers to an optical field with modulated phase and amplitude, characterized by distinct spatial patterns. It has applications in optical manipulation, 3D imaging, remote sensing, and communications. The Generalized Lorenz-Mie Theory (GLMT) extends foundational Mie theory to accommodate complex structured lights, enabling precise characterization of structured light-particle interactions. GLMT has emerged as a central theoretical framework for analyzing interactions between spherical particles and arbitrary structured light. This paper introduces ABSphere, simulation software utilizing GLMT to model structured light-spherical particle interactions. It then comprehensively reviews representative structured lights, including Laguerre–Gaussian, Bessel, and Airy beams, elucidating their interactions with spherical particles. Understanding structured light scattering behavior is crucial for elucidating underlying interaction mechanisms with spherical particles. The paper also emphasizes the significance of modeling structured light scattering by particles and discusses future directions for ABSphere software. Through continuous theoretical refinements and advancements, deeper understanding of structured light-particle interaction mechanisms can be achieved, enabling innovations in optical applications and technologies.

Sub-wavelength focused light and optical trapping application based on two-mode interference from an optical micro-/nanofiber

The ability to focus light on a subwavelength scale is essential in modern photonics. Optical microfiber-based sub-wavelength focusing will allow a miniaturized, flexible and versatile tool for many applications such as biomedical imaging and optomechanics. For a separate mode exited from an optical micro-/nanofiber endface, the photons will experience significant diffraction into the free space. This situation can be changed by incorporating two-mode interference along with the specific spatial distributions of both <i> <b>E</b> </i>-field amplitude and phase. Herein we report a novel approach to realizing sub-wavelength focusing based on the two-mode interference exited from an optical microfiber endface. By utilizing specific distributions of <b><i>E</i></b> -field amplitude and phase of two interacting optical modes, interference field patterns with a single focus (e.g., via a two-mode set of HE<sub>11</sub> and HE<sub>12</sub>) or multiple foci (e.g., via a two-mode set of HE<sub>11</sub> and HE<sub>31</sub>) can be obtained. Then, it is proved that the constructed foci will readily facilitate and selective trapping of nanoparticles. Circular polarization of optical mode is utilized in order to bring in angular symmetry of sub-wavelength focusing patterns compared with linear polarized optical modes. Our simulation results show that the smallest focal spot produced from the EH<sub>11</sub> and HE<sub>12</sub> mode interference has a full width at half-maximum (FWHM) of ~ 348 nm (i.e. 0.65<i>λ</i>). Such a subwavelength focusing field is applied to the optical trapping of an 85 nm-diameter polystyrene nanosphere. Further calculation reveals that the stable trapping can be fulfilled with axial and transverse trap stiffness of 11.48 pN/(μm·W) and 64.98 pN/(μm·W), as well as axial and transverse potential well of 101 <i>k</i><sub>B</sub>T/W and 641 <i>k</i><sub>B</sub>T/W via two-mode interference of HE<sub>11</sub> and HE<sub>12</sub>. These values demonstrate the great improvement over conventional tapered fibers. Further investigations show that different foci, via a two-mode set of HE<sub>11</sub> and HE<sub>31</sub>, exhibit unlike trap stiffness and potential wells, justifying the potential for nanoparticle size sorting. Based on the flexible all-fiber device, this subwavelength focusing strategy by two-mode interference may find promising applications in optical manipulation, superresolution optical imaging, data storage and nanolithography.

Dynamics of quadratic phase controlled Hermite-Gaussian beams in fractional systems based on different variable coefficients and potentials

The Hermite-Gaussian (HG) beam has many potential advanced applications in optical communications, electron acceleration, nonlinear optics and bio-optical disease detection, owing to its distinctive mode and intensity distribution. The research on HG beam are significant in the development of optics, medicine and quantum technology. However, the controlling of the evolutions of HG beam with quadratic phase modulation (QPM) in fractional systems under variable coefficients and potentials has been rarely studied. In this work, the propagation dynamic behaviors of the HG beam with QPM are investigated based on the fractional Schrödinger equation (FSE) under different variable coefficients and potentials by using a split-step Fourier algorithm. In the free space, the focusing spot of the beam becomes larger as the positive QPM coefficient increases or the Lévy index decreases. The QPM coefficient has little effect on the focusing amplitude when the Lévy index is 2. When the QPM coefficient is negative, the focusing of the beam disappears. Under the joint action of cosine modulations and QPM, the transmission of the beam oscillates not by the cosine law, but presents a large and a small breathing structure. The positive and the negative coefficient of QPM only alter the breathing sequence. The evolution period and width of the beam decrease as the modulation frequency increases. The trajectory of split beams turns into a parabolic shape under the linear modulation. In the joint influence of linear modulations and QPM, the HG beam exhibits either focusing or not focusing. Furthermore, the focusing position and focal plane of the beam decrease as the Lévy index increases. When the Lévy index is small, the beam keeps a straight-line transmission without distortion at a longer distance under the joint effect of the power function modulation and a positive QPM. The transmission of the beam also stabilizes and the beam width becomes larger with a negative QPM. Under a linear potential, the splitting of the HG beam disappears with the increase of the linear coefficient and shows a periodic evolution. The propagation trajectory of the beam shows a serrated pattern. By adding QPM, the beam is significantly amplified. Additionally, the evolution period of the beam is inversely proportional to the linear coefficient, and the transverse amplitude turns larger as the Lévy index increases. The interference among beams is strong, but it also exhibits an autofocus-defocusing effect under the joint action of a parabolic potential and QPM. In addition, the positive coefficient and the negative coefficient of QPM only affect the focusing time of the beam. The frequency of focusing increases as the Lévy index and parabolic coefficient rise. These features are important for applications in optical manipulations and optical focusing.

Liquid crystal micro-Fresnel zone plate with fine variable focusing properties

This study presents a liquid crystal micro-Fresnel zone plate (LC-MFZP) with fine variable focusing properties. The LC-MFZPs are fabricated via photochemical processes without any mechanical process. The focusing properties are investigated through numerical simulations and experiments. LC-MFZPs can generate a focusing spot with a specific incident wavelength such that the transmitted phase difference between their adjacent ring zones is π rad. When this difference is changed by the electrical reorientation of the LCs, the focusing spot disappears because the diffraction condition is no longer satisfied. Subsequently, another focusing spot at a specific incident wavelength is generated to satisfy the diffraction condition. The positions of these focusing spots differ because the focal lengths depend on the incident wavelength. Consequently, LC-MFZPs can be used to electrically control the focal length. This study may find applications in optical manipulation and optical trapping.

Epicycle-model-guided arbitrary shaped customization of structured light

Structured light has been exploited as an important tool for particle manipulation along a desired complex path. However, generating the required structured light illumination for the creation of an arbitrary shape without an analytic expression as a guide is challenging, specifically for designing a structured beam by mapping the shape of an arbitrary object. To address this issue, we propose an effective scheme to customize structured light freely and precisely by modifying the epicycle model in astrophysics. Predesigned structured beams can be identified with or without explicit analytic expressions of the desired shapes. Moreover, we study the roles and relationships between the number of epicycles and the number of key points. The local stretching and transformation of a specific structured beam are also analyzed. The advantages of the proposed method are demonstrated by conducting dynamic manipulation experiments using polystyrene particles. This method is simple and intuitive and provides an effective toolkit for the design of structured light for more complex tasks, thus facilitating advanced applications in optical manipulations.

Rotating axis measurement based on rotational Doppler effect of spliced superposed optical vortex

Abstract In most rotational Doppler effect (RDE) measurements, the optical axis and the rotating axis of the object are required to be aligned. However, the condition is very difficult to achieve in practical applications of rotation detection, which seriously affects the received signal. Moreover, it is necessary to focus the beam on the rotating axis of a rotating surface in applications ranging from manufacturing to physical experiments. For example, the manufacture of diffraction optical elements requires aligning the beam to the rotating axis of the spindle. Therefore, how to determine the azimuth of the rotating axis has become an urgent problem to be solved. Based on a new type of superposed vortex beam with multiple topological charges (TCs), we report a new scheme for determining the position of rotating axis by only single RDE measurement, which greatly improves the measurement efficiency. According to the mode decomposition and conservation of angular momentum and energy, we reveal the RDE mechanism of the new structured beam named spliced superposed optical vortex (SSOV) and explain why the SSOV with asymmetrical defect is sensitive to the rotating axis of the object. In addition, in order to prove the effectiveness of the method, a proof-of-concept experiment is conducted to detect the position of object’s rotating axis in eight azimuth ranges, i.e., [iπ/4, (i + 1)π/4](i = 0, 1, 2, 3, 4, 5, 6, 7). The idea of breaking the symmetry of the optical vortex (OV) and adding additional parameters in this study may have great potential for applications in optical manipulation and communication. Finally, considering that the orbital angular momentum (OAM) mode purity and quality of the incomplete OV and the SSOV will decrease during the far-field propagation, a new method for pre-correction of SSOV is proposed in this research, which overcomes the effects caused by Gouy phase shift and diffraction to some extent. Combined with inertial navigation, these methods above can also be applied to remote sensing, manufacturing, and physics experiments.

Optical Manipulation of Nanoparticles: A Selective Excitation Approach Using Highly Focused Orbital Angular Momentum Beams

Orbital angular momentum and polarization states of highly focused vector vortex beams can be engineered to selectively excite the desired multipoles in nanoparticles, making them ideal candidates for complex optical applications. A platform based on the generalized Lorenz–Mie theory integrated with the complex source point method is developed to model the interaction of such beams with particles analytically. The existing platform is extended for obtaining the full‐vector electromagnetic fields, outlining the observed effects that adding a substrate brings to the problem space. Despite the cross‐coupling between different multipoles induced by the substrate, it is concluded that the proper choice of beam parameters enables the selective excitation of multipoles even in the critical case of a plasmonic substrate. The proposed formalism is general and allows a multipole study of the optical forces. Selective excitation is exploited to control the imparted optical forces on particles placed on a plasmonic substrate. 3D trapping regions are achievable for highly absorptive and high‐refractive‐index particles. Motion trajectory analyses are performed to demonstrate the trapping stability, concluding that highly focused optical beams, owing to the exceptional selective excitation ability, are suitable candidates for novel optical manipulation applications.

Controllable self-rotating array beam with an arc-shaped accelerating trajectory.

In this study, a modified interfering vortex phase mask (MIVPM) is proposed to generate a new type of self-rotating beam. The MIVPM is based on a conventional and stretched vortex phase for generating a self-rotating beam that rotates continuously with increasing propagation distances. A combined phase mask can produce multi-rotating array beams with controllable sub-region number. The combination method of this phase was analyzed in detail. This study proves that this self-rotating array beam has an effectively enhanced central lobe and reduced side lobe owing to adding a vortex phase mask compared with a conventional self-rotating beam. Furthermore, the propagation dynamics of this beam can be modulated by varying the topological charge and constant a. With an increase in the topological charge, the area crossed by the peak beam intensity along the propagation axis increases. Meanwhile, the novel self-rotating beam is used for optical manipulation under phase gradient force. The proposed self-rotating array beam has potential applications in optical manipulation and spatial localization.

Optical force exerted on the two dimensional transition-metal dichalcogenide coated dielectric particle by Gaussian beam

Two-dimensional transition-metal dichalcogenide (TMDC) exhibits a series of distinctive optical and electrical characteristics, which make it has a good application prospect in the field of optical manipulation. Based on the Mie theory, we investigate the radiation force exerted on the TMDC wrapped dielectric particle by Gaussian wave. Theoretical calculations show that the optical force spectra exhibit two resonant peaks in the visible region, which are generated by the interband exciton transitions in TMDC. Magnitude and morphology of the excitonic peaks could be modulated effectively by tuning the number of coated TMDC layers. Furthermore, the excitonic peaks transform significantly with particle size due to the variation of coupling strength between the dielectric particle and TMDC coating. The investigation provides potential applications in optical manipulations and light-matter interactions.

Optical Bottle Shaping Using Axicons with Amplitude or Phase Apodization

We investigate the formation of single and multiple optical bottle beams on the optical axis using a diffractive axicon with amplitude or phase apodization. The proposed approach allows one to control the location and the contrast of the boundaries of the generated dark intensity regions on the optical axis. Experimental results obtained using a spatial light modulator are in good agreement with numerically obtained ones. We successfully used the designed and experimentally formed set of three optical bottle beams for trapping light-absorbing agglomerations of carbon nanoparticles in air under the action of photophoretic forces. This confirms the efficiency of the proposed approach for optical manipulation applications.

Generation of higher-order Laguerre–Gaussian modes from a diode-pumped Pr3+:LiYF4 laser with an intra-cavity spherical aberration

We demonstrate, for the first time to the best of our knowledge, the direct generation of higher-order Laguerre–Gaussian (LG) petal modes, formed of the coherent superposition of positive and negative LG modes with the topological charge of ± ℓ as an eigen mode, from a compact diode end-pumped P r 3 + : L i Y F 4 (YLF) laser with an intra-cavity lens configuration. The on-axis displacement of the intra-cavity lens with spherical aberration allows the selective operation of the desired higher-order LG modes with | ℓ | ≤ 31 from the laser cavity at 640 nm and 607 nm. Such visible higher-order LG modes will offer new applications in optical manipulation, quantum/optical underwater telecommunication, and microfabrication.

Generating Ultralong-Superoscillation Nondiffracting Beams with Full Control of the Intensity Profile

Nondiffracting light beams receive substantial attention in various areas due to their properties of diffractionless propagation and achievable subwavelength beam size. Extending the propagation distance and compressing the beam size of nondiffracting beams are crucial to their practical applications. However, it remains challenging to achieve nondiffracting light beams with a subwavelength subdiffracting transverse size and a long propagation distance with controllable intensity profiles in both transverse and longitudinal directions. Here, we propose an optimization method to generate an ultralong-superoscillation nondiffracting light beam with full control of the beam intensity profile. A 45\ensuremath{\lambda}-long-superoscillation nondiffracting light beam, the transverse sizes of which are within the range of 0.37\ensuremath{\lambda}--0.4\ensuremath{\lambda} along the propagation axis, is experimentally demonstrated by a metalens based on continuous phase modulation using geometrical phase metasurfaces. Our method provides an attractive way to controllably generate ultralong-superoscillation nondiffracting beams on a subwavelength scale and might find fascinating applications in optical manipulation, materials processing, data storage, microscopy, and spectroscopy.

Statistical properties of a partially coherent vector beam with controllable spatial coherence, vortex phase, and polarization.

We report on a partially coherent radially polarized power-exponent-phase vortex (PC-RP-PEPV) beam with various distributions of intensity, controllable coherence width, vortex phase, and polarization. The statistical properties of the PC-RP-PEPV beam depend on topological charge, power order, polarization states, and coherence width, which differ from those of conventional radially polarized beams. Here, the initial radial polarization state will transform to complex ellipse polarization state during propagation. By modulating the topological charge of the PC-RP-PEPV beam, the intensity structure of the beam can be adjusted from circular to polygonal. Finally, PC-RP-PEPV beams were experimentally generated, and were consistent with numerical simulation results. This work has applications in optical manipulation, optical measurements, and optical information processing.

Circular Airy beam with an arbitrary conical angle beyond the paraxial approximation

An arbitrary conical angle is introduced to the circular Airy beam (CAB) beyond the paraxial approximation, with the possibility to demonstrate its obvious tunability for the propagation properties of the CAB. The expressions are worked out to describe the electric field based on the angular spectrum representation, where a closed-form approximation of the angular spectrum is derived by using the stationary phase method. It is found that the nonparaxiality becomes obvious for large conical angles. In particular, the field intensity at the focal point can be enhanced about 10 times with respect to the conventional CAB by simply tailoring the conical angle. Meanwhile, the longitudinal component of the field is enhanced and gradually plays a leading role as the conical angle is increased. Moreover, the longitudinal gradient of the field intensity is also enlarged for large conical angles, suggesting a stable optical trapping for microparticles, which may find many applications in optical manipulations.

Propagation dynamics of Laguerre-Gaussian beams in the fractional Schrödinger equation with noise disturbance.

The evolution of Laguerre-Gaussian (LG) beams in the fractional Schrödinger equation (FSE) with Gaussian noise disturbance is numerically investigated. Without noise disturbance, the peak intensity of LG beams increases with the increment of radial or azimuthal indices, and the turning point of the peak intensity between different radial indices exists. As propagation distance gets longer, the intensity of the outermost sub-lobe exceeds that of the main lobe. When Gaussian noise is added, for a given noise level, the stability of peak intensity is enhanced as the Lévy index increases, while the center of gravity shows the opposite phenomenon. Moreover, the increment of the radial index can weaken the stability of the center of gravity. We also investigate the stability of the peak intensity of Airy beams in the FSE, and generally, the stability of LG beams is better than that of Airy beams. All these properties show that LG beams modeled by the FSE have potential applications in optical manipulation and communications.

Chiral discrimination by polarization singularities of a metal sphere

The practical applications of chiral discrimination are usually limited by the weak chiral response of enantiomers and the high complexity of detection methods. Here, we propose to use the C lines (i.e., lines of polarization singularities) emerged in light scattering by a metal sphere to detect small chiral particles. Using full-wave numerical simulations and analytical multipole expansions, we determined the absorption dissymmetry of deep-subwavelength helices (i.e., chiral particles) at different positions on the C lines. We find that the absorption dissymmetry can be much larger than that induced by circularly polarized plane wave excitation, and it can be attributed to the asymmetric absorption of the induced electric and magnetic dipoles. We also show that the absorption dissymmetry strongly depends on the anisotropy of the helices. The results may find applications in optical manipulations, optical sensing, and chiral quantum optics.

Quasi-perfect vortices generated by Pancharatnam-Berry phase metasurfaces for optical spanners and OAM communication

Optical vortex (OV) can be used in the fields of optical manipulation and optical communication because of its inherent orbital angular momentum (OAM). The size of the OV ring increases with the correlated topological charge (TC), making the OV with large TC not suitable for optical rotation and short-distance communication. Perfect vortex (PV) has attracted much attention due to that its optical transmission profile is almost independent of TC. In this manuscript, we proposed a method to generate quasi- perfect vortices (Q-PVs) by Pancharatnam–Berry (PB) phase metasurfaces, the so-called Q-PV can be regarded as an annularly focused optical vortex whose focal ring in the focal plane has an angular phase gradient. It has a similar property to PV in that its light profile hardly changes with TC in the focal plane. We demonstrated that the Q-PV can be used for optical spanners that particles are trapped and rotated on the specific orbit. Non-coaxial and coaxial Q-PV arrays were further generated for OAM communication applications. We believe that the proposed Q-PVs has potential applications in optical manipulation and optical communication.

Controllable multi-point light focusing of feedback wavefront shaping based on phase superposition Hadamard encoding algorithm

To achieve controllable multi-point light focusing, we develop a new feedback wavefront shaping optimization algorithm called phase superposition Hadamard encoding algorithm (PS-HEA). This algorithm combines the phase superposition method with the Hadamard encoding algorithm, and uniformity coefficient H is introduced to improve the uniformity of multi-point focusing. With the PS-HEA algorithm, we experimentally realized uniform focusing and multi-point customized intensity ratio focusing of light through the scattering medium and demonstrated the strong anti-noise and light control capabilities of PS-HEA in multi-point light focusing. Our research may pave the way for potential applications of optical manipulation and optogenetics.

Orbital angular momentum and beyond in free-space optical communications

Abstract Orbital angular momentum (OAM), which describes tailoring the spatial physical dimension of light waves into a helical phase structure, has given rise to many applications in optical manipulation, microscopy, imaging, metrology, sensing, quantum science, and optical communications. Light beams carrying OAM feature two distinct characteristics, i.e., inherent orthogonality and unbounded states in principle, which are suitable for capacity scaling of optical communications. In this paper, we give an overview of OAM and beyond in free-space optical communications. The fundamentals of OAM, concept of optical communications using OAM, OAM modulation (OAM modulation based on spatial light modulator, high-speed OAM modulation, spatial array modulation), OAM multiplexing (spectrally efficient, high capacity, long distance), OAM multicasting (adaptive multicasting, N-dimensional multicasting), OAM communications in turbulence (adaptive optics, digital signal processing, auto-alignment system), structured light communications beyond OAM (Bessel beams, Airy beams, vector beams), diverse and robust communications using OAM and beyond (multiple scenes, turbulence-resilient communications, intelligent communications) are comprehensively reviewed. The prospects and challenges of optical communications using OAM and beyond are also discussed at the end. In the future, there will be more opportunities in exploiting extensive advanced applications from OAM beams to more general structured light.