Bessel Beams Research Articles

Fabrication of customized microneedle with high 3D capability and high structural precision

Advanced 3D fabrication techniques are essential for the processing of 3D devices, which mainly focusing on excellent 3D fabrication capability and high structural precision. Although 3D printing technology allows for the creation of complex 3D structures with extensive customization, it faces notable challenges in achieving precise micro/nanostructures within materials due to incomplete resin curing bonds. Here, we propose integrating projection micro-stereolithography (PμSL) with femtosecond (fs) laser Bessel beam drilling to create 3D structures with advanced customization, precise structures (including size accuracy and aspect ratio), and efficient processing. Starting with the drilling process using Bessel beams, we have achieved micro-holes with a diameter of approximately 1μm and the aspect ratio reached 1017:1 on 3D printed items by regulating the transparency and elasticity of the products. Furthermore, we have applied this technology to produce tailor-made microneedles, including slanted-tip microneedles and porous microneedles, demonstrating its ability for extensive, efficient micro-hole processing with a peak drilling speed of 200,000 holes per second. This technology offers an innovative approach to creating three-dimensional devices with intricate cavity structures, and its impressive processing capabilities suggest potential for broad industrial implementation.

Multichannel full-space coding metasurface with linearly-circularly-polarized wavefront manipulation

Abstract Achieving independent multitasked wavefront control by using an ultrathin plate is a challenge to increase information capacity in integration optics and radar applications. Transmission-reflection-integrated metasurface provides an efficient recipe primarily for multifunctional meta-device, however it is challenging to synergize both linear polarization (LP) and circular polarization (CP) using a single meta-plate. Here, a multichannel full-space coding metasurface composed of interleaved shared-aperture meta-atom is proposed to achieve large information capacity by capsulating judiciously engineered high efficiency triple sub-elements (modes) in four-layer scheme. By rotating dual-gap split ring resonator and varying size of “L” type structure insulating by a metallic ring with electrostatic-analogue shielding effect, both Pancharatnam–Berry (PB) and dynamic phases are independently realized under CP and LP waves, respectively. Such an extraordinary insulating strategy completely suppresses crosstalk among three modes and unprecedentedly increases the capability in yielding kaleidoscopic wavefront control. To verify the significance, a proof-of-concept metadevice is devised and experimentally demonstrated with tri-channel wavefront manipulations, exhibiting reflective dual-vortex beam and Bessel beam for forward and backward CP wave, respectively at high frequency, while transmissive polarization beam splitting for 45°-LP wave at low frequency. Our finding in polarization-direction multiplexing is expected to generate great interest in electromagnetic integration with emerging degree of freedoms.

Higher order Bessel beams integrated in time (HOBBIT) with engineered light frequencies (ELFs)

Higher order Bessel beams integrated in time (HOBBIT) with engineered light frequencies (ELFs)

Dual-control of incubation effect for efficiently fabricating surface structures in fused silica

Abstract Fused silica with surface structures has potential applications in microfluidic, aerospace and other fields. To fabricate structures with high dimensional accuracy and surface quality is of paramount importance. However, it is indeed a challenge to strike a balance between accuracy and efficiency at the same time. Here, a temporally shaped femtosecond laser Bessel-beam-assisted etching method with dual-control of incubation effect is proposed to achieve this balance. Instead of layer-by-layer ablation continuously with Gaussian pulses, silica is modified discretely by double pulse Bessel beam with one single layer. During the modification process, incubation effect is dual-controlled in single shot process and spatial scanning process to generate even modified region efficiently. Then, the modified region is etched to form designed structures such as microholes, grooves, etc. The proposed method exhibits high efficiency for fabrication of surface structures in fused silica.

Overcoming the trade-off between signal-to-noise ratio and resolution in holographic registration of pulsed terahertz Gauss–Bessel beams

Overcoming the trade-off between signal-to-noise ratio and resolution in holographic registration of pulsed terahertz Gauss–Bessel beams

Sub-terahertz near field channel measurements and analysis with beamforming and Bessel beams

Sub-terahertz communications (100–300 GHz) are explored today as a candidate technology to enable extremely high-rate, low-latency data services and high-resolution sensing in beyond-fifth-generation (beyond-5G) wireless networks. However, these sub-terahertz wireless systems will often have to operate in the near field, where the signal propagation does not follow canonical far-field models, including the commonly used free space path loss equation. Instead, the signal propagation in the near field follows more complex patterns that are not well-captured with analytical far-field models standardized for 5G research. Moreover, state-of-the-art beamforming solutions exploited heavily in fourth-generation (4G) and 5G networks are notably less efficient in the near field. In this article, the near-field sub-terahertz channel is accurately measured and analyzed. In addition to state-of-the-art beamforming, the article also analyzes the sub-terahertz channel measurements when using near-field-specific Bessel beams that demonstrate fewer power fluctuations in the near field in addition to higher focusing gain. Novel distance-centric and angle-centric dependencies reported in this article may serve as a reference when developing next-generation channel models for sixth-generation (6G) and beyond-6G near-field sub-terahertz wireless systems.

Self-healing Bessel-Gaussian beam generation based on multimode interference effect

Two typed Bessel-Gaussian beams with good non-diffraction and self-healing properties have been generated by using tapered hollow tubes with double layers. The evolution process of light propagation in the tapered hollow tube cavity is studied theoretically. The theoretically analysis and simulation results show that the Bessel-Gaussian beam generation is due to the multimode interference. Two typed Bessel-Gaussian beams are generated by changing the inner layer thickness of such hollow tubes, which both experiences autofocusing at the output port and evolve into Bessel-Gaussian beams. The effect of single and multiple silica particles on their self-healing performance has also been analyzed, which has a good property for ultrafast laser micromachining.

Perfect vortex beams generation based on reflective geometric phase metasurfaces

Perfect vortex beam (PVB) is a propagating light field with radial intensity distribution independent of topological charge and carrying orbital angular momentum (OAM). PVBs can be generated through the Fourier transformation of a Bessel-Gaussian (BG) beam, which traditionally requires a precisely aligned optical setup consisting of a spiral phase plate, a conical lens, and a Fourier lens. However, such traditional schemes are usually bulky and unstable. Here, we have utilized a method that differs from conventional approaches, employing metasurfaces designed as planar Pancharatnam-Berry (PB) phase elements to substitute for all the required components. Unlike traditional methods based on reflective or refractive elements, metasurface elements can significantly reduce the system's footprint. Because the use of metallic metasurfaces allows for a more flattened design plane, in this paper, we have demonstrated the generation of PVB within the 8 GHz microwave frequency band based on a single-layer metallic metasurface. The metasurface is composed of a square ring metal structure, which can serve as a half wave plate to provide the required geometric phase distribution for incident circularly polarized light to generate PVB. By rigorously optimizing the parameters of the square-ring structures, we have generated vortex beams carrying OAM with different topological charges. These vortex beams exhibit a constant radial intensity distribution, which validates their "perfect" characteristics. In addition, we also extracted the mode purity of different vortex beams, so that the mode states of different vortex beams can be distinguished. These results provide broader value for the application of perfect vortex beams in communication.

Sub-area design of a reflective metasurface for Bessel beam generation to mitigate the impact of feed occlusion

Sub-area design of a reflective metasurface for Bessel beam generation to mitigate the impact of feed occlusion

Benchmarking of hydrodynamic plasma waveguides for multi-GeV laser-driven electron acceleration

Hydrodynamic plasma waveguides initiated by optical field ionization have recently become a key component of multi-GeV laser wakefield accelerators. Here, we present the most complete and accurate experimental and simulation-based characterization to date, applicable to current multi-GeV experiments and future 100 GeV-scale laser plasma accelerators. Crucial to the simulations is the correct modeling of intense Bessel beam interaction with meter-scale gas targets, the results of which are used as initial conditions for hydrodynamic simulations. The simulations are in good agreement with our experiments measuring evolving plasma and neutral hydrogen density profiles using two-color short pulse interferometry, enabling realistic determination of the guided mode structure for application to laser-driven plasma accelerator design. Published by the American Physical Society 2024

Acoustofluidic Virus Isolation via Bessel Beam Excitation Separation Technology.

The isolation of viruses from complex biological samples is essential for creating sensitive bioassays that assess the efficacy and safety of viral therapeutics and vaccines, which have played a critical role during the COVID-19 pandemic. However, existing methods of viral isolation are time-consuming and labor-intensive due to the multiple processing steps required, resulting in low yields. Here, we introduce the rapid, efficient, and high-resolution acoustofluidic isolation of viruses from complex biological samples via Bessel beam excitation separation technology (BEST). BEST isolates viruses by utilizing the nondiffractive and self-healing properties of 2D, in-plane acoustic Bessel beams to continuously separate cell-free viruses from biofluids, with high throughput and high viral RNA yield. By tuning the acoustic parameters, the cutoff size of isolated viruses can be easily adjusted to perform dynamic, size-selective virus isolation while simultaneously trapping larger particles and separating smaller particles and contaminants from the sample, achieving high-precision isolation of the target virus. BEST was used to isolate severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from human saliva samples and Moloney Murine Leukemia Virus from cell culture media, demonstrating its potential use in both practical diagnostic applications and fundamental virology research. With high separation resolution, high yield, and high purity, BEST is a powerful tool for rapidly and efficiently isolating viruses. It has the potential to play an important role in the development of next-generation viral diagnostics, therapeutics, and vaccines.

Gravitational waves from high-power twisted light

Recent advances in high-energy and high-peak-power laser systems have opened up new possibilities for fundamental physics research. In this work, the potential of twisted light for the generation of gravitational waves in the high frequency regime is explored for the first time. Focusing on Bessel beams, novel analytic expressions and numerical computations for the generated metric perturbations and associated powers are presented. The gravitational peak intensity is shown to reach 1.44×10−5 W m−2 close to the source, and 1.01×10−19 W m−2 ten meters away. Compelling evidence is provided that the properties of the generated gravitational waves, such as frequency, polarization states, and direction of emission, are controllable by the laser pulse parameters and optical arrangements. Published by the American Physical Society 2024

Tunable Photonic Hook Design Based on Anisotropic Cutting Liquid Crystal Microcylinder

The selective control and manipulation of nanoparticles require developing and researching new methods for designing optical tweeters, mainly based on a photonic hooks (PHs) effect. This paper first proposes a tunable PH in which a structured beam illuminates an anisotropic cutting liquid crystal microcylinder based on the Finite-DifferenceTime-Domain (FDTD) method. The PHs generated by plane wave, Gaussian, and Bessel beam are analyzed and compared. The impact of beams and LC particle parameters on the PHs are discussed. Where the influence of the extraordinary refractive index (ne) on PHs is emphasized. Our results reveal that introducing birefringence can change the bending direction of PH. Besides, the maximum intensity of the PHs increases as ne increases regardless of the beam type. The PH generated by a plane wave has a higher maximum intensity and smaller FWHM than that generated by the Gaussian and Bessel beams. The smallest FWHM and maximum intensity of the PHs generated by the Gaussian falls between that generated by the plane wave and the Bessel beam. The PH generated by a Bessel beam has the minor maximum intensity and the largest FWHM. Still, it exceeds the diffraction limit and exhibits bending twice due to its self-recovery property. This paper provides a new way to modulate PH. This work offers novel theoretical models and the degree of freedom for the design of PHs, which is beneficial for the selective manipulation of nanoparticles. It has promising applications in Mesotronics and biomedicine.

Bessel beams generation with biphase transition of vanadium dioxide metasurface

Bessel beams are highly attractive due to their non-diffraction properties, parallel processing capabilities, and large capacity. However, conventional methods for generating Bessel beams, such as using spatial light modulators, axicons, and diffraction optical elements, face limitations in terms of system complexity, bulkiness, low uniformity, and limited numerical aperture (NA). In this work, we exploited the phase change material vanadium dioxide (VO2) to generate both transmitted and reflected Bessel beams. Moreover, the self-healing property of Bessel beams was verified. Our results reveal that VO2 in the insulating state achieves a transmittance of 85% in the transmitting mode, while VO2 in the metallic state exhibits a reflection efficiency of 77% in the reflecting mode. This performance indicates the potential applications in efficient switchable metasurfaces.

Bessel beam propagation using radial beam propagation method at different propagation scales

This paper is devoted to studying the Bessel beam propagation in cylindrical coordinates using the Hankel transform beam propagation method (HT-BPM) and their behavior in different scenarios in the microscale and meter scale of propagation distances. The study compares the results obtained from the HT-BPM with another fast Fourier transform beam propagation method (FFT-BPM) to validate the accuracy and effectiveness of the HT-BPM in modeling Bessel beam propagation. The axial intensity of Bessel beam propagation is analyzed using the HT-BPM. The simulation results obtained from the HT-BPM are compared with those from the FFT-BPM to evaluate the agreement and consistency between the two methods in predicting the axial intensity of Bessel beam propagation. The results show that the HT-BPM is numerically faster than the FFT-BPM by ten times for different sampling points, furthermore, the FFT-BPM accuracy for evaluating the Bessel beam spot radius is 89.9% of the analytical value, while the HT-BPM is 99% relative to analytical value. The prediction of the axial intensity of the Bessel beam has been tested at different types of phase functions and different propagation distances: micrometer, centimeter, and meter scales. The results of the HT-BPM are matched with the analytical and experimental values. Finally, the HT-BPM is tested when the input light source takes different profiles.

Propagation dynamics and radiation forces of circular Bessel Gaussian beams carrying power-cotangent-phase vortices

Propagation dynamics and radiation forces of circular Bessel Gaussian beams carrying power-cotangent-phase vortices

High Uniformity Bessel Beams with Angle-Controllable Steering

High Uniformity Bessel Beams with Angle-Controllable Steering

Spatiotemporal characteristics of magneto-acousto-electric fields generated by Bessel beams

The magneto-acousto-electric (MAE) effect shows great significance in neural modulation, whereas the high-precision stimulation cannot be realized by the unidirectional electric distribution perpendicular to the orthogonal acoustic and magnetic fields. A new MAE model is established based on helical wave fronts of Bessel beams in a coaxial magnetic field. Numerical and experimental studies are conducted for quasi-Bessel beams constructed by the saw-tooth phase modulation for a sectorial planar transducer array in a coaxial toroidal magnet. The MAE field induced by the Bessel beam of lth order is determined by those of (l-1)th and (l + 1)th orders. The rotary MAE field with a constant peak-intensity center can only be constructed by the Bessel beam of 1st order, which is effective for neural stimulation. Assisted by therapeutic effects of center-captured drug particles by acoustic-vortex tweezers, the center-converging MAE field may advance a new collaborative stimulation strategy with improved accuracy and reduced acoustic energy.

Bessel-Beam Single-Photon High-Resolution Imaging in Time and Space

Synchronous laser beam scanning is a common technique used in single-photon imaging where the spatial resolution is primarily determined by the beam divergence angle. In this context, Bessel beams have been investigated as they can overcome the diffraction limit associated with traditional Gaussian beams. Notably, the central spot of a Bessel beam retains its size almost unchanged within a non-diffractive distance. However, the presence of sidelobes in the Bessel beam can negatively impact spatial resolution. To address this challenge, we have developed a single-photon imaging system with high-depth resolution, which allows for the suppression of echo photons from the sidelobe light in the depth image, particularly when their flight time differs from that of the central spot. In our LiDAR setup, we successfully achieved high-resolution scanning imaging with a spatial resolution of approximately 0.5 mm while also demonstrating a high-depth resolution of 12 mm.

Facile fabrication of THz metasurfaces by a spatially shaped femtosecond laser printing system

Terahertz (THz) metasurfaces provide unprecedented abilities to realize versatile THz wavefronts manipulations. Nevertheless, these high degree of freedom, non-periodic, densely arranged subwavelength unit cells pose numerous extreme parameter requirements for the fabrication of metasurfaces, presenting significant challenges to their practical application. Herein, a spatial shaping femtosecond laser printing system, based on spatial light modulation (SLM), is proposed for the creation of THz metasurfaces. Through programming the SLM with a sequence of computer-generated holograms (CGH) corresponding to C-shaped Bessel beams with varying opening angles and orientation angles, the C-shaped slit resonant rings with different geometric parameters—fundamental units of the metasurface—were precisely printed onto a gold film. To validate this technique, a THz metalens based on a phased gradient design and a THz holographic plate employing simultaneous phase and amplitude modulation were meticulously fabricated, displaying outstanding performance. Owing to the simple processing flow, high reproducibility, and wide applicability of materials, this technique stands out as a versatile and efficient approach for fabricating THz metasurfaces, with the potential to promote the commercialization of terahertz metasurfaces.