This PDF file contains the front matter associated with SPIE Proceedings Volume 12606, including the Title Page, Copyright information, Table of Contents, and Conference Committee information.

We demonstrated the visualization of quantized vortices in superfluid helium with silicon nanoparticles. Nanoparticles were produced in situ with pulsed laser ablation and dispersed within the superfluid helium. The dispersed nanoparticles were utilized to decorate the quantized vortices, allowing for the imaging and visualization of the dynamics of the vortices, such as vortex reconnection.

In recent years, optical holographic data storage system has gradually become a research hotspot and a strong competitor of big data storage due to its high data transfer rate, long storage life and high storage density. In the collinear amplitude modulated holographic data storage system, in order to improve the storage density, a high magnification objective lens is usually used as the recording lens to record the encoded data pages in the holographic storage medium. Therefore, when the objective lens is focused on the holographic storage medium, the accuracy and reliability of data recording and reading can be guaranteed. However, in the process of normal use of the system, environmental interference and other factors will inevitably lead to defocusing of the objective lens, which will result in high bit-error-rate (BER) and low signal-to-noise ratio (SNR) of the recorded and read coding information, affecting the accuracy and reliability of information reading. In this paper, we propose a collinear amplitude modulated holographic data storage system objective defocusing correction model using deep learning. Only a training model with defocusing distance of 100μm can be used to correct the defocusing of the objective lens with defocusing distance less than 100μm. The reconstructed BER is reduced to less than 1/10 of the original data, and the SNR is increased to more than 5 times of the original data. The reliability and accuracy of system record reading are improved.

Phenanthraquinone-doped poly (methyl methacrylate) (PQ/PMMA) photopolymers have been considered a promising holographic recording medium for polarization holography due to their neglectable shrinkage, controllable thickness, and photoinduced anisotropy. Past studies have demonstrated that the polarization properties of PQ/PMMA materials are caused by the anisotropy of the photosensitizer PQ molecules. In addition, when measuring the photobirefringence value of the PQ/PMMA material, we can obtain a curve of photobirefringence values that is positively correlated with time. We prepared a new photopolymer material based on PQ/PMMA material. Specifically, we introduced the photoinitiator Triethanolamine (TEA) on the basis of PQ/PMMA material. Then we use the experimental optical path to record two beams of the orthogonal polarization interference light. By measuring the polarization state of diffracted light and the photoinduced birefringence curve of the material, we found the negative photoinduced birefringence phenomenon in PQ/PMMA material for the first time.

Simultaneous use of magnetism and photoluminescence (PL) of spinel ferrites must be attractive especially in clinical medicine. We synthesized spinel ferrites containing Cd, Cu, and Cr, that is, Cd_0.5Cu_0.5Cr_0.05Fe_1.95O₄ , by the chemical co-precipitation method; then the as-prepared material was sintered; these as-prepared and sintered materials were characterized using powder X-ray diffraction (powder XRD) and scanning electron microscopy (SEM); also, the physical properties were evaluated using vibrating sample magnetometry (VSM) and PL spectroscopy.

In the holographic data storage system, we can use deep learning method to learn the relationship between phase patterns and their near-field diffraction intensity images. In the practice, pixel crosstalk always exists. We found the pixel crosstalk between adjacent variable phase pixels was benefit for quick and accurate phase retrieval based on deep learning. We validated our idea by the simulation of adding phase disturbance between pixels on the spatial light modulator.

Polarization holography can record and reconstruct information by means of polarization state modulation. It can record the amplitude, phase and polarization information of light field by recording the polarization grating of two coherent waves with different polarization states. This technology has been used to record two or four pairs of 2-level grayscale images in the case of two or four channels in the past. Now we designed experiments to record and reconstruct two different 4-level grayscale images at the same point of polarization-sensitive media through the faithful reconstruction of linearly polarization holography by matching the exposure time and the polarization angles of the two interference waves. We verify that it is possible to reconstruct two 4-level intensity images at the same point to achieve polarization and intensity multiplexing.

Surface features of natural materials such as cuticles, shells, and leaves continue to be used as models for creating sophisticated infrastructure, landscape, and microdevice designs. Optical microscopy is the easiest and most accessible tool for examining such surface features and micropatterns. This method, however, fails to probe opaque surfaces like thick skin and leaves since it needs enough light to penetrate the sample. In this work, we demonstrate the feasibility of probing the natural structures of a superhydrophobic leaf using simple optical microscopy by replicating the leaf surface on an elastomer via soft lithography. Optical images of the replica revealed intricate details of features present on the leaf, including the stoma, cuticle boundary, and trichome. Contact angle measurements were also conducted to investigate the wettability of the real leaves and their replicas. Finally, we utilized the fabricated replicas as optical gratings that were observed to generate various diffraction patterns with fluctuating intensities. Our work offers a new perspective on alternative optical microscopy strategies and optical beam tuning using biomimetic, low-cost materials.

This paper investigates the variable polarization of linearly polarized waves reconstructed via photorefractive volume holography. Linear polarization states were recorded inside an iron-doped lithium niobate crystal and reconstructed. Diffraction efficiencies were measured. Results revealed that there are statistically significant shifts in reconstructed polarization states.

Optical trapping and rotation of resonant nanoparticles combined with determination of its internal and external temperatures create a perfect platform for study of rheology, temperature and basic thermodynamics in the micro- and nanoscale.

We present optical trapping and levitation of silver-coated hollow glass spheres using a LG₀₁ vortex laser. We successfully levitate reflective targets ranging from 53μm to 93μm in diameter with powers ranging from 50mW to 1W. Our system is designed for long working distance trapping (40mm-100mm) which is desirable for in-vacuo alignment and manipulation of mass-limited microtargets for high energy plasma applications, by limiting optical component damage from high-intensity light-matter interactions.

We show a new class of nanogap antenna structure that has chiral dissymmetry - the field intensity at the nanogap is high for a particular handedness of circularly polarized incident light, while not for the other. To find such a structure, we employed a computational inverse design technique, called topology optimization. With circularly polarized incident light, we found the mathematical algorithm is capable to find a complex spiral-like structure that is difficult to attain only by our intuition or knowledge. We calculated the field enhancement at the nanogap to evaluate dissymmetry against the handedness of the circular polarization. The resultant factor of dissymmetry was as high as 1.40, demonstrating the validity of the chiral antenna structure as well as the topology optimization techniques for the design problem of nanophotonic structures involving a complex electromagnetic field such as circular polarization or optical vortex.

Controlling the motion of materials using fluorescence can open up new directions in optical manipulation. However, fluorescence is a stochastic process, and the net force on a large number of emitters becomes necessarily small. To solve this problem, we formulate optical force induced by superfluorescence, which is a synchronous photoemission. By using the formulation for a simple model, we find that, when the emitters are properly placed, the forces on each emitter exhibit synchronous behavior as well as the fluorescence dynamics, causing a significant net force.

We present the first demonstration of the 2-dimensional fabrication of surface reliefs with spiral two-, four-, and six-arms, named "galaxy-shaped surface relief," in an azo-polymer film by employing petal-like modes formed of the superposition of positive and negative Laguerre-Gaussian modes. This demonstration provides new physical insights into the interaction of light and matter to develop rewritable optical data storage with ultrahigh data capacity.

Micro-manipulation enables us not only to move micro-objects but also control flow in micro-scale. Micro-scaled flow plays an important role in a wide range of fields including microfluidic devices and microbiological systems. Although these systems are frequently placed in viscous or complex fluids, micro-scaled flow in complex fluids have not been studied much compared to that in a simple liquid. In this study, we experimentally studied flow field induced by an optical driven nematic liquid crystal (NLC) droplet in an aqueous glycerol solution. The rotation of the droplet can be controlled with circularly polarized light. In a viscous fluid, slip at the surface of the droplet was observed and the slip velocity increased with the rotation speed of droplet, Due to the slip, the magnitude of flow velocity induced by the rotating droplet becomes smaller than that in water. As an application of the rotating NLC droplet, we used it for micro-viscometry. The estimated viscosity in an aqueous glycerol solution by micro-viscometry is quantitatively compared with the literature value. The difference between them is discussed by slip effect. This technique leads to further investigation for local viscosity in soft matter.

We develop a generalized optimisation algorithm based on gradient ascent to design mode sorters and optical circuits using multi-plane light conversion. We experimentally demonstrate the sorting of photons based on their orbital angular momentum state, Zernike mode, step-index multimode fibre (MMF) mode, or, most generally, a random spatial mode basis of up to 55 modes. In simulations, we showcase the future potential of these devices to undo the scrambling introduced by the propagation of light through optical fibres: we design a passive device, which we term an optical inverter, that is complementary to a MMF and reverses its scrambling effect on light. We describe how this enables real-time imaging directly through MMFs.

In this work, we have studied the dynamics of 7-ions Ca⁺ Coulomb crystal in a linear quadrupole trap with flat end-cap electrodes. We have introduced geometrical parameters to determine points of phase transitions in the crystal. Then we have numerically calculated a phase diagram for this case and simulated the corresponding Coulomb crystals. It was shown that new one-dimensional radial Coulomb crystals are observed with the application of both high end-cap voltage (more than 1200 V) and a bias voltage on linear electrodes.

Spin angular momentum (SAM) of light only has a longitudinal component for paraxial waves, but the transverse component of the SAM can be significant in a strongly confined light field. Here, we experimentally demonstrate the spinning of an anisotropic particle – bipolar liquid crystal (LC) - by trapping it using a circularly polarized optical tweezers and observe the dependence of the particle’s spinning rate on different laser powers and different states of input polarization. Furthermore, we detect the transverse spin of light by measuring the rotation frequency of a trapped liquid crystal particle, placed in the vicinity of the evanescent field near an optical nanofiber surface using optical tweezers. This result demonstrates that the transverse spin of light can twist anisotropic particles.

A method to change the scatterer distribution of a random laser medium using the optical trapping technique is proposed. By focusing trapping beams into small regions of the scattering medium, some scattering particles are concentrated in those regions, causing inhomogeneous distribution of scatterers. We investigate the effect of the scatterer distribution formed by optical trapping on the emission spectrum of a random laser. Experimental results show that the spectral spike intensity of random lasers with trapped particles is higher than that for the random lasers without trapped particles. Furthermore, the spectral spike intensity depends on the power of the trapping spot. The relationship between the number and the intensity of spikes in the emission spectra shows a feature observed in other random lasers with inhomogeneous scatterer distributions.

The proposal of the research is used localized surface plasmon resonance (LSPR) of gold nanoparticles (Au NPs) modified Cuprous Oxide/Zinc oxide nano-rod array (Cu₂O/ZnO NRA) composite electrode to apply in non-enzymatic glucose sensor. An anodic aluminum oxidation (AAO) method is used for growing aluminum array holes, then ZnO is grew in these holes by hydrothermal method to form ZnO NRA. Cu₂O is electrodeposited on ZnO NRA at different pH values from 4 to 10. Au NPs are prepared by chemical synthesis and is uniformly dispersed on the surface of Cu₂O/ZnO NRA by Nafion dispersant. The stability and linearity of the glucose sensing electrode of Cu₂O/ZnO composite materials are improved by utilizing the catalytic, stable and high-sensitivity characteristics LSPR of Au NPs. Scanning electron microscope (SEM) is used to check the array hole size of the AAO. A sorption spectrum of ZnO is used to verify the energy gap. The sensor would be tested by the chronoamperometry method with the increasing of glucose concentration. The calibration curve of glucose sensor has linear ranges: 7.41-11.111 mM and the sensitivity of 315.67 μA/M^-1 cm^-2.

A non-contacting method to manipulate and array many nanoparticles is an important subject for physics, chemistry, and biology. The optical manipulation and binding provide rich functionalities and degrees of freedom to form a ordered assembly of particles by combining with heat generation, hydrodynamic effect, chemical reaction, etc. In this study, we extend a concept of the optical binding to achieve a wide-area particle formation by an optical method. In contrast to a conventional optical binding with a wide-area laser irradiation, we consider a tightly focal laser irradiation, where one or a few gold particles are directly trapped at the focal center and the others are bound indirectly at the out of irradiation area. For the indirect binding, the interference in multiple scattering is significant. The bound particles revolve by the spin angular momentum of laser. The revolution is stable dynamics since the revolution axis is well defined. For the focal laser, we have several control parameters, e.g., NA, focal depth, and number of beams. Then, we consider the optical binding by two focal laser beams. This extension brings an increase of control parameters. We focus on the circular polarized two lasers with seven particles binding in the respective irradiation area. The scattered light from one laser spot disturbs the dynamics of particles at other laser spot and revolution is frozen in each other. It suggests a nonlocal optical manipulation. When the lasers become close, 14 particles form a single stable array. It enables an on-demand formation of particle array.

Nanoscopic observation of chiro-optical phenomena is an intriguing scientific topic but have large difficulties in the measurements, and hence the physics is still largely unexplored. So far, the chiro-optical physics have not been well unveiled; conventionally, those phenomena have been investigated only through indirect information from the macroscopic far-field optical measurements and/or predictions by theoretical simulations. To fully understand and to utilize the full potential of chiro-optical systems, the local in-situ observation of the effects from individual components is essential, as the macroscopic chiro-optical effect is not straightforward for the analysis of the microscopic phenomena. In the present study, we attempted the imaging of the chiro-optical forces confined in the nanospaces based on a photoinduced force microscopy. On the right-handed gammadion structure, the strong optical gradient force appeared at the edges of the structure under illumination of LCP light at 785 nm. The left-handed gammadion gave the similar result under RCP illumination. This research paves the way for clarifying the physics of nanoscale chiro-optics and application of that.

We report on the direct generation of higher-order cylindrical vector vortex modes at red (640 nm) from the Pr³⁺:LiYF₄ (Pr³⁺:YLF) laser with an intra-cavity plano-convex spherical lens. Desired cylindrical vector vortex mode is selectively generated from the laser cavity appropriately by adjusting an on-axis position of the intra-cavity lens. Our laser system can operate at single and superposed vector vortex modes. Such compact and cost-saving vector vortex laser source can be easily integrated to any commercial device for applications.

Optical vortex laser-induced forward transfer (OV-LIFT), in which light field with a helical wavefront is employed instead of a plane wave, enables the high-definition direct print of a variety of donor materials with high spatial resolution, however, its mechanism has not been fully understood yet. We herein demonstrate, for the first time, the numerical simulation model of OV-LIFT based on the simulation technique of thermo-fluid dynamics, including mass transport equation. Temporal evolution of the droplet ejection by the illumination of optical vortex pulse is successfully reproduced. Such numerical simulation model will enable the further improvements of OV-LIFT performances to develop advanced direct print technology for printed electronics, photonics and biotechnology.

There are many ways to realize null reconstruction in polarization holography, which can be divided into two types. One is the null reconstruction without exposure response coefficient constraint, and the other is the null reconstruction limited by the exposure response coefficient. On the basis of previous studies, we have further studied these two types of null reconstruction, and obtained the necessary conditions for realizing the two types of null reconstruction under arbitrary interference angle and polarization state.

The scanning probe microscopy with the optical cavity composed of the metal tip and metal substrate enables to obtain a high-resolution image and access the microscopic information from light and matter interaction. Tip-enhanced photoluminescence (TEPL) provides the spectroscopic image of photoluminescence with sub-nm resolution and the individual state of a single molecule. To discuss the microscopic optical response in the TEPL, we develop a theoretical framework based on nonlocal response theory and input-output theory. From the elementary model of calculation, we can successfully obtain the spatial distribution of the transition dipole of the selectively excited molecule.

We demonstrate single droplet formation in an ionic liquid/water mixture by optical tweezers. Upon focusing a near-infrared laser beam into the aqueous solution, a liquid droplet is formed at the focal spot. The droplet is stably trapped and increases in its size. The growth rate becomes faster at the higher laser power. The droplet has a core in its inside. The core-shell structure is confirmed by transmission and fluorescence imaging. We discuss the droplet formation dynamics from the viewpoints of optical force and local temperature elevation.

We demonstrate, for the first time, 2-dimensional (2D) direct print of perfect circle microdots consisting of close-packed Au nanoparticles by employing the optical vortex induced forward transfer (OV-LIFT). Going beyond the ink-jet printing technology, the OV-LIFT allows the direct print of ultrafine microdots with a diameter of ~8 μm and an ultralow positional error of <7 μm.

Magnetic trapping and optical manipulation of micro-particles are combined in superfluid helium. Irradiation of pulsed light to a magnetically trapped superconducting particle causes simple damped oscillation of the particle. The analysis of the trajectory gives rise to the estimation of viscosity of the superfluid helium along with some properties of the trapped particle.

In this paper, we propose a super-resolution holographic data storage system based on deep learning. A low-pass filter was introduced into the Fourier plane to remove the high frequency. This produces a blurred intensity image of the reconstructed beam. A convolutional neural network is used to establish the relationship between the blurred intensity image and the data page. The encoded phase data page can be directly demodulated from a captured intensity image, which is a non-interferometric method without iterations. The function of the filter is to generate the blurred intensity image and to reduce the recording area to improve the recording intensity. Usually, the limit of the aperture is the Nyquist size. Here, by introducing embedded data on the phase data page, the aperture size of the recording can be reduced to smaller than the Nyquist size. A simulation experiment was established to verify the effectiveness of the proposed method.

Since photons have momentum, luminescence from materials should also act to induce optical force, which we call luminescence-induced optical force (LiOF). LiOF occurs by designing an anisotropic dielectric structure surrounding an emitter. As a model, we assumed a square-type optomechanical resonator formed with the luminescent nanofilm and a metallic mirror substrate. Then, we theoretically calculated the LiOF exerted on the film and revealed that the LiOF could drive the vibrational motion of the luminescent film as an oscillator. In addition, we showed that LiOF caused the mechanical frequency shift of the oscillator, known as optical spring effect. This study will provide new insights into developing an unconventional type of optomechanics.

Critical Casimir forces emerge between objects, such as colloidal particles, whenever their surfaces spatially confine the fluctuations of the order parameter of a critical liquid used as a solvent. These forces act at short but microscopically large distances between these objects, often reaching hundreds of nanometers. Keeping colloids at such distances is a major experimental challenge, which can be addressed by the means of optical tweezers. Here, we review how optical tweezers have been successfully used to quantitatively study critical Casimir forces acting on particles in suspensions. As we will see, the use of optical tweezers to experimentally study critical Casimir forces can play a crucial role in developing nanotechnologies, representing an innovative way to realize self-assembled devices at the nano- and microscale.

In this paper, we propose a simple model for describing an axis-symmetric thermal convection in a micro channel caused by a photothermal effect, namely, a temperature increase of the fluid due to a laser irradiation. The model consists of two planer solid parts (a microchannel), a thin planer fluid film between the solids, and a focused laser irradiated perpendicularly to the fluid film as a heat source; this is a typical geometrical setting found in various optical trapping experiments. The model describes the flow field and the solid and liquid temperatures. Assuming that the nonlinear convection terms are negligible due to the microscale confinement, the present fluid model is analyzed by two methods: one is a semi-analytical approach and the other is the direct numerical simulation. The validity of the both methods are shown by comparing the results of them, and a typical example of laser-induced thermal convection is presented. The semi-analytical approach is instant and therefore useful even for researchers without the background of fluid mechanics and can be used for systematic prediction of the photothermal fluid phenomena.

Neurons in the brain communicate by releasing and receiving neurotransmitters at synapse. Synaptic vesicles (SVs) that encapsulate neurotransmitters play an important role for neuronal communication. We demonstrate that optical trapping of synaptic vesicles in cultured rat hippocampal neurons regulates the neuronal network activity. The neuronal electrical activity was evaluated by extracellular potential measurement using microelectrodes arrays (MEAs). When a near-infrared trapping laser was focused on synaptic vesicles labeled with FM1-43 dye, fluorescence caused by two-photon absorption was observed at the focal spot. The fluorescence intensity gradually increased during the laser irradiation time at the laser power of 500 mW, indicating that optical trapping forces cause the assembly of SVs at the focal spot. In the extracellular potential measurement of neuronal electrical activity, spike number of spontaneous neuronal activity increased under optical trapping of SVs. The synchronicity of neuronal network activity by cross-correlation analysis increased after the laser irradiation under higher laser power conditions. These results suggest that neuronal electrical activity can be manipulated by optical trapping of synaptic vesicles.

Optical trapping realizes the formation of a unique spiral-structured crystal of ethylenediamine sulfate (EDS). When a continuous-wave laser beam of 1064 nm is tightly focused at the air/solution interface of EDS aqueous saturated solution, the EDS crystal is induced at the laser focus and is grown by further laser irradiation, and the crystal growth with a spiral structure is observed. Intriguingly, the preliminary experimental data suggest that the growth direction of spiral- structured crystal corresponds to the handedness of circular polarization of the incident light. We propose that the growth direction is determined by the transfer of the angular momentum of incident circularly polarized laser to the growing crystal due to crystal birefringence.

One-dimensional photonic crystals have been frequently used as optical filters and in sensing technology due to their ability to induce highly reflective photonic bandgaps. Conventionally, at least two materials are required to create the necessary dielectric contrast for photonic bandgaps to form. Recently, one-dimensional photonic crystals fabricated by two-photon polymerization have demonstrated the ability to induce photonic bandgaps with reflectances over 90%. Using this fabrication approach, dielectric contrast is achieved by altering the density of adjacent layers from a single photo-sensitive polymer. The success of this technique has led to the development of design modifications which allow additional spectral control of the photonic bandgap. In this study, we combine these concepts to develop a one-dimensional photonic crystal which includes a mechanical defect for the first time. Mechanical control of this defect allows for the presence of the transmissive defect mode to be actively shifted in and out of the photonic bandgap. The fabrication of this structure as well as its characterization is reported and discussed. The results of this study further support the use of one-dimensional photonic crystals in opto-mechanical applications where switchable narrow transmission bands are desired.

Local heating of degassed water produces a water vapor microbubble and significant flow around it. However, this flow is strongly attenuated by the substrate on which the bubble is generated. The flow speed is proportional to the -3 power of the distance from the bubble. In this study, the bubble was generated using a thin, tapered optical fiber. The FeSi₂ thin film was deposited on the fiber tip to heat the fiber tip using the photothermal conversion property of the film. As a result, a water vapor microbubble was generated on the fiber tip with a diameter of 28 μm. The flow speed around the bubbles was proportional to the -1.2 power of the distance from the bubbles. It exceeded 80 mm/s even at 200 μm away from the bubble.

Full Poincaré beams (optical skyrmions), in which all polarization states on the Poincaré sphere are projected onto the beam cross section, exhibit exotic vectorial structures, and they will offer fundamental physics as topological quasiparticles and advanced technologies, such as optical data storage, optical/quantum communication, and encryption with the freedom of skyrmion states. We here propose a robust and cost-saving system to generate versatile optical skyrmions by employing a spatial light modulator (SLM) with a self-referenced interferometric configuration. We demonstrate the generation of optical skyrmions, formed of a fundamental Gaussian and a first-order Laguerre-Gauss modes, as evidenced by a linearly polarized spiral spatial form and orthogonal Stokes parameters.

In this contribution, we reveal a mechanism of light-induced acceleration of antigen-antibody reaction by enhancing the collisions of probe particles and target proteins under the optical and fluidic pressures in microchannel, which leads to the attogram-level detection. The clarified mechanism enables the selective detection of 10¹-10² ag target proteins in sub-microlitter liquid sample with 1-2 orders higher sensitivity and ultrafast specific detection only by 3 minutes of laser irradiation in the absence of any pretreatment procedures in comparison with a conventional immunoassay requiring a few hours. The obtained results will facilitate the development of proteomics and innovative platforms for a variety of biochemical reactions leading to the early diagnosis of various diseases (cancer, dementia, and microbial infections etc).

Optical condensation is a method for the rapidly and densely assembling dispersoids on the substrate. Recently, we developed the metallic nanofilm-coated optical fiber (MNOF) module to perform optical condensation on the three-dimensionally arbitrary position in dispersion liquid although the convection profile was limited in the case of a two-dimensional photothermal source. In this work, we investigate the effect of interface on the optical condensation using MNOF by changing the position from the substrate. Remarkably, the assembly efficiency of optical condensation with MNOF can be 1 to 2 orders of magnitude higher than that of conventional optical condensation two-dimensional case. These results will lead to a high-performance analysis of various small objects, such as microbes and biomaterials.

Despite the apparent simplicity, the problem of refraction of electromagnetic waves at the planar interface between two media has an incredibly rich spectrum of unusual phenomena. An example is the paradox that occurs when an electromagnetic wave is incident on the interface between a hyperbolic medium and an isotropic dielectric. At certain orientations of the optical axis of the hyperbolic medium relative to the interface, the reflected wave is completely absent. In this paper, we formulate the aforementioned paradox and present its resolution by introduction of infinitesimal losses in a hyperbolic medium. We show that the reflected wave exists, but became extremely decaying as the loss parameter tends to zero. As a consequence, all the energy scattered into the reflected channel is absorbed at the interface. We support our reasoning with analytical calculations, numerical simulations, and an experiment with self-complementary metasurfaces in the microwave region.

A birefringent twister combines a birefringent element and a cylindrical lens to realize a stable twisting interferometer. We report numerical simulation for a birefringent twister for Gaussian beam and Laguerre-Gaussian beam inputs.

We fabricate single-chip, high-purity, high-power optical vortex beam generators by integrating a spiral phase plate onto the emission surface of photonic-crystal surface-emitting lasers, and we evaluate their far-field images and phase characteristics.

Angular momentum of light has been applied to various applications such as mechanical motion manipulation, optical communication, and sensing. Furthermore, we have proposed that it is possible to form optical fields with angular momentum in nanometer scale area using plasmonic fields of multimer nanoantennas and have succeeded in experimentally manipulating orbital rotation of nanoparticles and controlling the chirality of crystals. However, the angular momentum of light is converted due to the interaction between light and matter in the process of transmission from incident lights to the plasmonic fields, and the laws of the conversion have not yet been clarified. To form plasmonic fields with the desired angular momentum on the nanometer scale, it is necessary to unveil thse conversion laws. Therefore, we analyzed the electromagnetic fields of the plasmonic fields of multimer nanoantennas and clarified the conversion law governing the spin and orbital angular momentum transfer. We also show that the interference of multiple fields with converted angular momentum enables the forming of nanometer scale fields with fractional angular momentum.

We report on the fabrication of a self-written microfiber waveguide with a first-order Bessel beam. The fabricated microfiber waveguide exhibits a diameter of ~7 μm and a millimeter-scale length. We also address the optical waveguide properties of the fabricated fiber.

We report on the interactions between internally driven pairs of active rotors in a dual optical tweezer. The active rotor is Bacillus subtilis, a wild-type, gram- positive bacterium that uses flagellar rotation for motility. A pair of bacteria are held at different distances and their respective flagellar rotations are studied through the durations of their approach and retraction from each other. The aim of our work is to investigate the nature of the interactions between two active confined rotors trapped in their pristine form. We find, that the frequency of the rotating flagella decreases in both confined bacteria on approaching each other and increases when retracted from each other. In other words, the flagellar rotations of a bacterium slow down while in the presence of a nearby neighbor and speeds up as the neighbor retreats. Our results show a similar trend as when compared to free swimming bacteria wherein they avoid each other on approach through modulation of their rotating flagella. We investigate through this setup the hydrodynamics mediated coupling between two such active rotors.

Nanodiamonds (NDs) containing silicon- or germanium-vacancy centers (SiV- or GeV-NDs, respectively) have shown promising potential as fluorescent markers for bioapplications. Recently fabrications of ~10 nm-sized SiV- and GeV-NDs were demonstrated by a detonation process that enables practical-scale NDs production. In the present study, the optical properties of the SiV- and GeV-NDs, a recent addition to the family of fluorescent NDs, were spectroscopically investigated. Their luminescence bands including each zero-phonon line commonly have small Debye-Waller factors (0.47 and 0.20, respectively) and broad linewidths (32 and 59 meV, respectively) at room temperature, comparing with those of typical SiV and GeV centers. These differences in the optical properties were due to the effects of lattice distortions and surface potentials from tiny-sized diamonds. The SiV- and GeV-NDs fabricated by the detonation process are interesting materials not only in the biomedical field but also in the study of optical manipulation.

Neuronal stimulation is essential to understand information processing in brain systems. Spatiotemporal patterns of neuronal activity can be modified by external stimuli. Recent studies have shown that neurons can be stimulated by short-pulse laser processing of the cell membrane. An optical vortex with a helical wavefront possesses an orbital angular momentum (OAM) enables the inward twisting of ablated materials, thereby processing further precisely cells beyond a conventional Gaussian beam. We herein study the mechanisms of neuronal stimulation with a focused nanosecond optical vortex. The focused nanosecond optical vortex on the cell membrane of rat hippocampal neurons induces extracellular Ca²⁺ influx and neuronal activity elicitation. Morphological changes of the neuronal cell membrane due to nanosecond optical vortex irradiation is also evaluated with fluorescence recovery after photobleaching. After the deposition of a single pulse of nanosecond optical vortex on the cell membrane of neurons, the fluorescence intensity of membrane probe at the focal region significantly decreases, however, it recovers within 5 seconds. Such dynamics suggests that the transient disruption occurs at the cell membrane based on laser ablation and recovers due to lateral diffusion of membrane molecules. The diffusion coefficients of membrane molecules after optical vortex irradiation are larger than those of Gaussian beam irradiation, and the disrupted membrane areas are smaller than the expected ones as the optical vortex focal region. These differences are attributed to the fact that the disruption of cell membrane owing to laser ablation and subsequent membrane diffusion are assisted by OAM transfer effects.

The speed of optical transportation of microparticles was modified by changing dissipative force acting on the particles through the switching of the absorption spectrum of molecules contained in the particles. Linear and orbital motions of microparticles in water were achieved by using slightly focused laser beams. Polymer microparticles containing photo-chromic molecules under the photoirradiation configuration were transported by the optical force due to scattering. The transportation speed was increased by changing the color of the particles by the photoinduced isomerization from transparent (non-resonant) to resonant with the manipulation beams.

We employ an off-center pumped Nd:YVO4/KGW Raman laser with stimulated Raman scattering and second-harmonic generation to generate high-order structured beams at 588 nm. The orange structured lights are transformed by using an external astigmatic mode converter for producing multiple optical vortices. We further verify that the experimental multi-vortex beams can be numerically reconstructed with the theoretical model, and the distribution of vortices is demonstrated by analyzing the phase structures of the converted beams.

Based on the correspondence between the conventional Poincaré and Bloch spheres, we proposed a higher-order Bloch spheres, which is an extension of the conventional Bloch spheres. By calculating the expectation value of the spin components using the Pauli spin matrices, we found that the new spin state is formed in a ring shape and the orientation of the spin changes depending on the azimuthal angle and topological charge of orbital angular momentum. We also realize the coherent transfer of the azimuth-dependent polarization state of photons to the electron spin state in a GaAs quantum well with a V-shaped three-level system.

The novel property of optical meta-devices, which consist of meta-antenna made by artificial nanostructures, has recently attracted lots of attention. The significant advantages of meta-devices are their new functionalities, lighter weight, small size, high efficiency, better performance, broadband operation, lower energy consumption, and CMOS compatibility for mass production. Given the demand for photonics, optical meta-devices for the application and control of incident light are being quickly developed for beam deflection and reflection, polarization control and analysis, holography, second-harmonic generation, laser, tunability, imaging, absorption, color display, focusing of light, multiplex color routing, and light-field sensing. Here we experimentally demonstrated the optical meta-devices in bio-photonics. We report three applications, varifocal Moiré meta-lens, meta-lens-based light-sheet fluorescent microscopy, and abrupt autofocusing meta-lens. We showed three optical meta-devices for bio-imaging, including varifocal, light-sheet, and abrupt autofocusing beams. Optical meta-devices have become a novel technique for in vivo imaging in cell biology research.

This study demonstrates the stability of three-dimensional optical topologies, making them ideal for use in secure communication channels that are prone to noise. The research investigates the stability of link and knot phase singularities when exposed to various types of aberration, providing valuable insights into their performance under perturbation. In addition, the study proposes a highly precise and efficient method for characterising complex bi-photon quantum states, which outperforms traditional quantum state tomography schemes. This novel approach allows for rapid reconstruction of structured entangled photon pairs, enabling researchers to more effectively engineer and utilise these quantum states for a wide range of applications.