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Two planar metasurface (MTS) antennas are designed to produce a pattern with optimal illumination in a radar scenario, given the a priori known path of the targets. The antennas are extremely flat, thin, with a monopole feed integrated in the plane of the structure. The monopole serves as a surface-wave (SW) launcher illuminating the slab. The excited SW progressively leaks after interacting with the MTS, forming a radiation pattern designed to cover uniformly a portion of road in a given scenario. The realized antennas radiation patterns are experimentally validated. The MTSs are then deployed in a frequency-modulated continuous wave (FMCW) radar system. The experiments showed that the echo of the targets in the range-Doppler map does not statistically depend on the distance between the target and the radar, while a clear range dependence is observed when classical patch array antennas are used. That means, given the capability to engineer a particular shape for the radiation pattern and the interest for simultaneously detecting small and big targets, the MTS antennas allow one to better resolve a small and distant target, next to a big and close one.

PURPOSE Cardiac computed tomography has a clear clinical role in the evaluation of coronary artery disease and assessment of coronary artery calcium (CAC) but the use of ionizing radiation limits the clinical use. Beam-shaping "bow-tie" filters determine the radiation dose and the effective scan field-of-view diameter (SFOV) by delivering higher X-ray fluence to a region centered at the isocenter. A method for positioning the heart near the isocenter could enable reduced SFOV imaging and reduce dose in cardiac scans. However, a predictive approach to center the heart, the extent to which heart centering can reduce the SFOV, and the associated dose reductions have not been assessed. The purpose of this study is to build a heart-centered patient positioning model, to test whether it reduces the SFOV required for accurate CAC scoring, and to quantify the associated reduction in radiation dose. METHODS The location of 38,184 calcium lesions (3151 studies) in the Multi-Ethnic Study of Atherosclerosis was utilized to build a predictive heart-centered positioning model and compare the impact of SFOV on CAC scoring accuracy in heart-centered and conventional body-centered scanning. Then, the positioning model was applied retrospectively to an independent, contemporary cohort of 118 individuals (81 with CAC > 0) at our institution to validate the model's ability to maintain CAC accuracy while reducing the SFOV. In these patients, the reduction in dose associated with a reduced SFOV beam-shaping filter was quantified. RESULTS Heart centering reduced the SFOV diameter 25.7% relative to body centering while maintaining high CAC scoring accuracy (0.82% risk reclassification rate). In our validation cohort, imaging at this reduced SFOV with heart-centered positioning and tailored beam-shaping filtration led to a 26.9% median dose reduction (25-75th percentile: 21.6%-29.8%) without any calcium risk reclassification. CONCLUSIONS Heart-centered patient positioning enables a significant radiation dose reduction while maintaining CAC accuracy.

The commonly used Gaussian intensity distribution during the laser-based processing of metals can negatively affect melt pool stability, which might lead to defects such as porosity, hot cracking, or poor surface quality. Hot cracking is a major factor in limiting production rates of high-strength aluminium alloys in laser-based processes such as welding or the powder bed fusion of metals (PBF-LB/M). Going away from a Gaussian intensity distribution to ring-shaped profiles allows for a more even heat distribution during processing, resulting in more stable melt pools and reduced defect formations. Therefore, the aim of this study is to investigate the influence of different laser beam profiles on the processing of high-strength aluminium alloys by using a multicore fiber laser, allowing for in-house beam shaping. Single weld tracks on the aluminium alloy EN AW-5083 are produced with varying laser powers and weld speeds, as well as different beam profiles, ranging from Gaussian intensity distribution to point/ring profiles. The molten cross sections are analyzed regarding their geometry and defects, and the surface roughness of the weld tracks is measured. By using point/ring beam profiles, the processing window can be significantly increased. Hot cracking is considerably reduced for weld speeds of up to 1000 mm/s compared to the Gaussian beam profile. Furthermore, the melt pool width and depth are more stable, with varying parameters for the point/ring profiles, while the Gaussian beam tends to keyhole formation at higher beam powers. Finally, a strong decrease in surface roughness for the point/ring profiles, accompanied by a significantly reduced humping effect, starting even at lower beam powers of 200 W, can be observed. Therefore, these results show the potential of beam shaping for further applications in laser-based processing of high-strength aluminium alloys.

International audience; We demonstrate a silicon (Si)-gallium arsenide (GaAs) semiconductor based holographic metasurface antenna operating at 94 GHz. The metasurface antenna molds the radiated beam by resorting to a holographic approach involving the modulation of a guided-mode generated by a pillbox beam former. The pillbox beam former is fed by three integrated horns in Substrate Integrated Waveguide (SIW) technology located in the focal plane of the parabolic reflector of the pillbox beam former. The three horns correspond to three independent beams and allow beam steering by switching from one feed to another. The proposed metasurface antenna is planar and extremely lowprofile, thus suitable for small platforms such as CubeSats/SmallSats. A prototype validates the concept demonstrating a directivity as high as 31.9 dBi and a reflection coefficient lower than-15 dB at 94 GHz.

Due to their subwavelength thickness, light weight and easy fabrication, metasurfaces show obvious advantages over 3D metamaterials. Among this, a new concept so-called digital coding metasurfaces ...

Sum and difference beams are two kinds of field patterns, which have been commonly used in monopulse radar systems for detecting and tracking targets. This letter proposes to synthesize sum and difference beams based on a binary programmable metasurface (BPM). Moreover, the sum and difference beams can be steered by reprogramming digital coding schemes of the BPM. A prototype of the BPM is designed and tested at the Ka-band. Both simulations and experiments validate the presented functions of beam shaping and beam steering.

Collimating lenses are an important component of laser ranging systems, and high overload environments severely affect the beam shaping effect of such lenses. This study proposes a buffer isolation method on the basis of impact stress wave attenuation theory for collimating lens spacers. ANSYS finite element software was applied to simulate the high load dynamics of collimating lenses, and the buffer isolation performance of different materials and composite structures was compared and analysed. Optical simulation analysis of the collimating lenses under different buffer conditions was performed using ZEMAX software to study the mechanism by which a high overload affects the collimating lenses. High overload and optical shaping experiments based on theoretical analysis were further conducted. Results showed the superiority of butadiene rubber to polytetrafluoroethylene after application of 70000 g impact acceleration. The combination-gasket method was superior to the single-gasket method, and the sandwich combination-gasket method was superior to the double-layer combination-gasket method.

A watt-level directly diode-pumped continuous-wave (CW) Ti:Sapphire oscillator was demonstrated for the first breakthrough by a high-power green laser-diode-pumped module employing the technologies of beam shaping, beam collimation, polarization beam combining, and fiber coupling. A 1.36-W output power and 10.6% of slope efficiency were obtained based on the double-concave (DC) cavity configuration. This is the highest CW output power from Ti:Sapphire (Ti:S) oscillator directly pumped by green laser diodes (LDs) reported so far.

Recent developments in laser beam sources expand the possibilities of laser beam welding of similar and dissimilar copper joints. New methods of beam shaping and adjustable intensity profiles using two layer fibers create a center and ring spot, which is the newest state of the art in fiber laser beam sources. In this study, the influences and possibilities of adjustable intensity profiles on the weldability of steel copper dissimilar lap joints with copper on the top side will be discussed. The results show that the former problems of spattering and poor beam coupling in copper can be avoided through new beam shaping technologies and adjusted parameter settings. In the investigations joints without melt ejections on copper surfaces of state of the art fiber laser technologies are demonstrated and the influence of different intensity distributions on the weld geometry will be discussed.

An approach to generate the tunable fractional vector curvilinear beams (VCBs) was proposed. The scheme is based on the vector optical field generator (VOFG) system, where the two orthogonal polarized scalar curvilinear beams (SCBs) are generated to be the base vector components, and coaxially superposed by a Ronchi grating. We design a new phase distribution with several loops of 0 to π in order to generate more dark gaps. The phase distribution becomes nonuniform by varying the phase variation rate and the positions of the dark gaps are changed. Using the different parameters of the curves, the fractional VCBs with different shapes are achieved. The two orthogonal polarized SCBs with the opposite topological charges are modulated to perform the beam conversion by a phase-only computer-generated hologram (CGH). Our experimental results comply with the theory and the radial opening of the dark gaps may have some applications for guiding and transporting particles.

Significance Fast submicrometer-scale 3D printing techniques are of interest for various applications ranging from photonics and electronics to tissue engineering. Interference lithography is a versatile 3D printing method with the ability to generate complicated nanoscale structures. Its application, however, has been hindered by either the complicated setups in multibeam lithography that cause sensitivity and impede scalability or the limited level of control over the fabricated structure achievable with mask-assisted processes. Here, we show that metasurface masks can generate complex volumetric intensity distributions with submicrometer scales for fast and scalable 3D printing. These results push the limits of optical devices in controlling the light intensity distribution and significantly increase the realm of possibilities for 3D printing., Fast, large-scale, and robust 3-dimensional (3D) fabrication techniques for patterning a variety of structures with submicrometer resolution are important in many areas of science and technology such as photonics, electronics, and mechanics with a wide range of applications from tissue engineering to nanoarchitected materials. From several promising 3D manufacturing techniques for realizing different classes of structures suitable for various applications, interference lithography with diffractive masks stands out for its potential to fabricate complex structures at fast speeds. However, the interference lithography masks demonstrated generally suffer from limitations in terms of the patterns that can be generated. To overcome some of these limitations, here we propose the metasurface-mask–assisted 3D nanofabrication which provides great freedom in patterning various periodic structures. To showcase the versatility of this platform, we design metasurface masks that generate exotic periodic lattices like gyroid, rotated cubic, and diamond structures. As a proof of concept, we experimentally demonstrate a diffractive element that can generate the diamond lattice.

Beam shaping is required for semiconductor lasers to achieve high optical fiber coupling efficiency in many applications. But the positioning errors on optics may reduce beam shaping effects, and then lead to low optical fiber coupling efficiency. In this work, the positioning errors models for the single emitter laser diode beam shaping system are established. Moreover, the relationships between the errors and the beam shaping effect of each shapers are analysed. Subsequently, the relationship between the errors and the optical fiber coupling efficiency is analysed. The result shows that position errors in the Z axis direction on the fast axis collimator have the greatest influence on the shaping effect, followed by the position errors in the Z axis direction on the converging lens, which should be strictly suppressed in actual operation. Besides, the position errors have a significant influence on the optical fiber coupling efficiency and need to be avoided.

[EN]High-harmonic generation (HHG) is a unique tabletop light source with femtosecond-to-attosecond pulse duration and tailorable polarization and beam shape. Here, we use counter-rotating femtosecond laser pulses of 0.8 µm and 2.0 μm to extend the photon energy range of circularly polarized high-harmonics and also generate single-helicity HHG spectra. By driving HHG in helium, we produce circularly polarized soft x-ray harmonics beyond 170 eV—the highest photon energy of circularly polarized HHG achieved to date. In an Ar medium, dense spectra at photon energies well beyond the Cooper minimum are generated, with regions composed of a single helicity—consistent with the generation of a train of circularly polarized attosecond pulses. Finally, we show theoretically that circularly polarized HHG photon energies can extend beyond the carbon K edge, extending the range of molecular and materials systems that can be accessed using dynamic HHG chiral spectro-microscopies, Department of Energy BES (DE-FG02-99ER14982); Air Force Office of Scientific Research (FA9550-16-1-0121); National Science Foundation (DGE-1144083, DGE-1650115); European Research Council (8511201); Ministerio de Ciencia, Innovación y Universidades (PID2019-106910GB-100); Junta de Castilla y León (SA287P18); Ramón y Cajal contract (RYC-2017-22745).

We report on a partially coherent power-exponent-phase vortex beam (PC-PEPV), whose spatial coherence is controllable and the initial phase exhibits a periodic power exponential change. The PC-PEPV beam was generated experimentally with various spatial coherence widths, and its propagation properties were studied both numerically and experimentally. By modulating the topological charge (TC) and power order of the PC-PEPV beam, the structure of the vortex beam can be adjusted from circular to elliptic, triangular, quadrangle, and pentagon. When the power order is odd, the PC-PEPV beam with a negative TC can be generated, and the profiles of the PC-PEPV beam can be precisely controlled via adjusting the value of the power order. For the case of high spatial coherence width, the number of the dark cores in the polygonal intensity array of the PC-PEPV beam equals the magnitude of the TC. However, when decreasing the spatial coherence width, the dark cores vanish and the intensity gradually transforms into a polygonal light spot. Fortunately, from the modulus and phase distributions of the cross-spectral density (CSD), both the magnitude and sign of the TC can be determined. In the experiment, the modulus and phase distribution of the CSD are verified by the phase perturbation method. This study has potential applications in beam shaping, micro-particle trapping, and optical tweezers.

Unlike the conventional design of aspheric shaping systems, in order to provide a laser source for applications such as multi-beam laser interference, which can maintain evenly distributed power over a large distance, the influence of shape parameter and aperture on long-distance propagation performance of Kepler refractive beam shaping system is studied. Current work describes the lens, designed automatically by using ZEMAX programming language (ZPL), and simulations of Kepler refractive shaping systems of flattened Lorenz (FL) beams with different shape parameters and apertures.

Optical tweezers are an established and extremely useful tool for manipulating microscopic particles with light. Optical tweezers systems regularly include optical components for creating complex structured light fields and detectors for measuring the resulting optical forces. Computational tools are often invaluable for generating and controlling structured light fields, modelling optically trapped particles and analysing experimental measurements.In this thesis I describe several computational tools and methods for modelling and controlling optical tweezers. There is a range of existing methods for simulating optical tweezers but there are relatively few general and easy to use tools. Here I describe two new open source toolboxes: a new version of the Optical Tweezers Toolbox (OTT) and a new beam shaping toolbox, OTSLM Toolbox for Structured Light Methods (OTSLM). These toolboxes enable the production and simulation of diverse structured optical fields. While existing tools tend to focus on particular hardware or demonstrating particular kinds of algorithms, these new toolboxes instead focus on usability and versatility for modelling a wide range of problems.Recently, machine learning has been very successful in modelling complex processes and solving difficult classification problems. Part of this thesis is dedicated to exploring how machine learning could be used to enable faster and more extensive optical tweezers simulations. One of the main problems with conventional methods is achieving sufficient accuracy without excessive runtimes. I demonstrate how machine learning can enable faster optical tweezers simulations and increase the range of tractable problems. Further still, I demonstrate how machine learning is useful for analysing optical tweezers measurements including for rapidly classifying optically trapped particles and improving force measurement accuracy.With these tools we are able to explore how particles scatter light, the dynamics of particles in optical traps, the accuracy of different measurement techniques and much more. Many of these application are demonstrated throughout this thesis and these simulations support, and are supported by, our groups recent experimental work.

Submicron long focusing range beams are gaining attention due to their potential applications, such as in optical manipulation, high-resolution lithography and microscopy. Here, we report on the theoretical and experimental characterization of an elastomeric polydimethylsiloxane/single layer graphene (PDMS/SLG) axicon-like tunable device, able to generate diffraction-resistant submicrometric spots in a pump and probe configuration. The working principle is based on the phase change of an input Gaussian beam induced in the elastomer via the thermo-optical effect, while the heating power is produced by the optical absorption of the SLG. The phase-modified beam is transformed by an objective into a long focus with submicron diameter. Our foci reach an experimental full width at half maximum (FWHM) spot diameter of 0.59 μm at the wavelength of 405 nm, with the FWHM length of the focal line greater than 90 μm. Moreover, the length of the focal line and the diameter of the focus can be easily tuned by varying the pump power. The proposed thermo-optical device can thus be useful for the simple and cheap improvement of the spatial resolution on long focus lines.

High thermal gradients and complex melt pool instabilities involved in powder bed fusion–based metal additive manufacturing using focused Gaussian-shaped beams often lead to high porosity, poor morphological quality, and degraded mechanical performance. We show here that Bessel beams offer unprecedented control over the spatiotemporal evolution of the melt pool in stainless steel (SS 316L) in comparison to Gaussian beams. Notably, the nondiffractive nature of Bessel beams enables greater tolerance for focal plane positioning during 3D printing. We also demonstrate that Bessel beams significantly reduce the propensity for keyhole formation across a broad scan parameter space. High-speed imaging of the melt pool evolution and solidification dynamics reveals a unique mechanism where Bessel beams stabilize the melt pool turbulence and increase the time for melt pool solidification, owing to reduced thermal gradients. Consequently, we observe a distinctively improved combination of high density, reduced surface roughness, and robust tensile properties in 3D-printed test structures.

This paper presents a summary of recent development of multi-functional metasurfaces at microwave frequencies, including direction-controlled, helicity-selective, and tunable metasurfaces. The design and experimental results of several illustrative multi-functional metasurfaces and their applications in focusing, beam shaping, and antenna designing are shown. These metasurfaces combine two or more wave functionalities into a single device, thus providing more flexibility in electromagnetic wave control, which is quite promising for many real-world applications.

OLEDs are thin-film devices consisting of multilayers of organic thin films sandwiched between a metal and an ITO electrodes. Because of the different refractive indices of the layers in the thin film stack, different optical modes are trapped in the device. In this talk, we will first discuss the physics of these optical modes and describe techniques to characterize them. We will then describe how to use various photonic structures to maximize the light output and manipulate these optical modes to control the polarization as well as directionality to achieve beam shaping.

Optical Coherence Tomography (OCT) is an imaging technique that performs high-resolution transverse and axial imaging of samples. We demonstrate a novel mechanical-scan free Spectral Domain OCT scheme that performs axial and transverse scans of the sample avoiding the use of any kind of mechanical platforms. The scheme makes use of a spatial light modulator in combination with some simple optical elements. This proof-of-principle demonstration can help usher in the development of alternative OCT schemes with potentially faster scan speeds than current OCT schemes by avoiding the use of any kind of mechanical platforms.

We proposed an automatic sorting method based on a virtual optical chip, which was formed by a complex-amplitude beam shaping system. The automatic sorting of different micro-particles was realized by the optical forces of the intensity and phase gradients of the reconstructed optical beam. The method was verified with theoretical analysis and experimental results. Compared with the traditional optical sorting methods, the proposed one does not need high-precision mechanical and/or microfluidic devices. The optical chip is flexible in structure and efficient in optical sorting and can be used in the fields of medical detection and material sensing.

Structured light fields have attracted much attention due to rich spatial degrees of freedom. The tailoring of an arbitrary structured light field on demand is the precondition for the application of structured light. Therefore, the computer holography method used to reconstruct a coherent light field wavefront has been naturally applied for generating structured light. In this work, we comprehensively demonstrate the principles and procedures of pure-phase computer-generated holography (PP-CGH) and binary-amplitude computer-generated holography (BA-CGH) methods for tailoring structured light, realized by two digitally programmable devices: liquid-crystal spatial light modulators (Lc-SLM) and digital micromirror devices (DMD), respectively. Moreover, we first compare the two approaches in detail and clarify the recipe to obtain a high tailoring accuracy and efficiency, which will help researchers to better understand and utilize the holographic tailoring of structured optical fields.

All-dielectric resonant metasurfaces has been emerging as a breakthrough platform for manipulating light, leading to advanced nanophotonic device architectures for lasing, ultrathin optical elements, beam shaping and sensing [1] - [3] . However, the current metasurfaces are often locked to a fixed functionality due to their static constituent materials, which severely limits the application range of these devices. Therefore, the development of novel dynamic metasurface designs is crucial to unleash the full potential of next-generation optical devices [4] .

Femtosecond laser modification of transparent materials offers selective chemical etching, facilitating three-dimensional (3D) micro-structures to open into flexible shapes as configured by multi-line scanning [1] . While surface aberration and other beam shaping methods have been widely studied in processing of transparent glasses [2] , [3] , the influence of such beam shaping on chemical etching has not been addressed. This paper examines the microstructure resulting in fused silica from beams with concave and convex conical phase front [4] . The conical beam shaping is shown to improve etching rates and surface morphology, compensate for deep focussing aberration and provide an attractive tailoring of the microchannel cross-sectional profile.

Planar diverging lenses attached to the front end of a dielectric rod antenna are proposed to control the heating area on the human body to assist the electroporation treatment of different tumor sizes. The desired 5–7 °C temperature elevation of the tumors is achieved in 3 minutes by applying 2.1-3.6 W input power depending on the size of tumor. In order to treat the tumors located 3–7 mm below the skin surface, the applicator is operated at 8 GHz. The experimental results obtained by measuring a pork muscle tissue show good agreement with electro-thermal simulations.

We report a novel beam homogenizer for digital micromirror device lithography system. Such a beam homogenizer contains only one random freeform microlens array (rfMLA). And the rfMLA consists of different freeform microlenses. By the individual design and irregular arrangement of the microlenses, efficient and uniform beam shaping results have been obtained, and the interference patterns in particular are greatly weakened. Compared with traditional beam homogenizer, the energy efficiency has been increased from 62.00% to 69.70%, and the uniformity for incoherent light and coherent light have been improved from 91.93% to 97.60% and from 79.00% to 94.33%, respectively. rfMLA has great potential for enhancing the performance of DMD lithography system and other optical systems, particularly for the homogenization of the beam and the integration of the system.

The Cu(In,Ga)Se2 (CIGS) thin film solar cell is a promising material architecture considering its high photovoltaic (PV) efficiency at low material cost. Recently, the authors demonstrated all lase...

Viewing the trend of beam shaping, beam steering, and metasurface holograms, a reconfigurable graphene-based metasurface is proposed and modeled using the method of moments combined with th...

A freeform lens construction is proposed to form a specific rotation symmetric beam profile with collimation in this paper. In the proposed approach, two freeform surfaces are constructed segment-by-segment using a numerical method based on Snell's law to produce an output beam profile which has both good irradiance uniformity and high collimation. It is shown that as the number of segments used to construct the freeform surfaces increases, the output beam profile approaches the specific profile. A sparse design point freeform surface construction method is additionally proposed which allows the beam profile to approach the desirable distribution with a fewer number of segments. The proposed method is used to construct freeform lenses for producing output beams with two user-defined irradiance patterns, i.e., annular and triangular distributions. The simulation results show that either demonstrated irradiance distribution is close to the specific distribution. Overall, the present results show that the proposed method provides a versatile and efficient approach for designing freeform lenses with a specific distribution of the output beam profile and good collimation.

Author(s): Bevins, JE; Sweger, Z; Munshi, N; Goldblum, BL; Brown, JA; Bleuel, DL; Bernstein, LA; Slaybaugh, RN | Abstract: An energy tuning assembly (ETA) was designed to be fielded at the National Ignition Facility (NIF) to modify the characteristic D-T fusion spectrum to include a prompt fission neutron spectral component. The ETA was characterized at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory to measure the shaped spectrum from an incident deuteron breakup neutron source, test the proposed neutron spectroscopy techniques used to inform the flux measurements at NIF, and validate the ability to predict ETA performance using a Monte Carlo Neutral Particle (MCNP) simulation. Activation foils (i.e., Ni, In, Au, Al) were exposed to a collimated 33-MeV deuteron-breakup beam originating from a tantalum breakup target. The source spectrum absent the ETA was characterized using a set of activation foils and the STAYSL unfolding code. Finally, the ETA-modified spectrum was obtained using activation foil unfolding with a [Formula presented]=1.32. The ETA-modified unfolded spectrum agreed with the MCNP-simulated prediction in the energy range of 0.1–14 MeV, but exhibited disagreements in the 10 eV–100 keV region. This work demonstrates shaping of the NIF neutron spectrum via the ETA to be a viable path forward for tailored neutron beams at NIF.

A method based on the electric field integral equation is proposed for synthesizing planar metasurface (MTS) antennas built on elliptical apertures. The MTS is modeled with a modulated tensorial surface impedance. Entire-domain basis functions are used to discretize efficiently the currents as well as the surface impedance, allowing a quasi-direct computation of the surface impedance from the desired radiation pattern. The corresponding surface currents are combined with the near-field radiation from a constant reactance to derive the surface impedance of the MTS. The obtained algorithm is, therefore, systematic and can be applied to generate arbitrary radiation patterns, with control on the amplitude, phase, and polarization. Numerical validation of the proposed technique illustrates the effectiveness of the method.

Laser cutting of metal sheets is a well-established industrial process, however, major process changes are constantly being introduced by newer technologies, e.g. new laser technologies, higher power sources, polarization and beam shaping control units, and gas flow optimizations. The multi-physical nature of the laser cutting process makes detailed simulations complex and demanding in terms of computational and implementation efforts. The gap between accurate modeling and industrial requirements makes an experimental approach often more economically realistic. Nevertheless, efficient assessment models that utilize a trade-off between model complexity and accuracy of the response to be assessed are attractive. Such models can be used for further technological development by efficiently supporting engineers in designing and selecting optical systems. This paper revisits model assumptions of an in-house developed laser cutting model as it is validated for larger thicknesses. This model assesses polarization and beam shaping effects on the cutting performance of thin sheets. In this work, dedicated cutting experiments to assess the maximum cutting speed of stainless steel 304L of 2, 6, and 10 mm thickness for a wide range of focal point positions are conducted and compared to the model prediction. The results show that R 2 of this comparison decreases from 0.99 for 2 mm thickness, to 0.58 for 10 mm. It can be concluded that the trend prediction accuracy degrades for thicker plates. Analysis of the experiments and simulation data for 10 mm plates reveals two possible phenomena that become more important with thickness: multiple reflections and instability of the melt flow dynamics. ispartof: pages:383-389 ispartof: Procedia Manufacturing vol:29 pages:383-389 ispartof: 18th International Conference on Sheet Metal, SHEMET 2019 location:Leuven, Belgium date:15 Apr - 17 Apr 2019 status: published

We propose a method based on neural network training algorithms for the design of diffractive neural networks - with the aim to perform advanced laser beam shaping in the NIR/VIS spectrum for laser materials processing. The method enables the efficient design of systems including multiple cascaded diffractive optical elements (DOEs) and allows the simultaneous optimization for complex (intensity and phase) target field distributions in multiple target planes. The multi-target boundary condition in the optimization method offers great potential for advanced laser beam shaping.

The genetic algorithm method is a new method used to obtain radiation beams that meet the IAEA requirements. This method is used in optimization of configurations and compositions of materials that compose double layered Beam Shaping Assembly (BSA). The double layered BSA is modeled as having two layers of material for each of the components, which are the moderator, reflector, collimator, and filter. Up to 21st generation, the optimization results in four (4) individuals having the capacity to generate the most optimum radiation beams. The best configuration, producing the most optimum radiation beams, is attained by using combinations of materials, that is by combining Al with either one of CaF2 and PbF2for moderator; combining Pb material with either Ni or Pb for reflector; combining Ni and either FeC or C for collimator, and FeC+LiF and Cd for fast and thermal neutron filter. The parameters of radiation resulted from the four configurations of double layer BSA adequately satisfy the standard of the IAEA.

Anomalous hollow beams in optical domain were introduced in Cai (2007) and Cai et al. (2008) and as an extension of anomalous hollow electron beams introduced in [Phys. Rev. Lett. 94, 134802 (2005)]. In this paper, for the first time, we demonstrate both theoretically and experimentally that we can obtain a flexible far-field anomalous hollow beam spot of elliptical symmetry with an elliptical solid core through incoherent superposition of two partially coherent sources with different degrees of coherence. The ellipticities and orientation angles of the outer elliptical ring and the inner elliptical solid core are controlled through varying the initial beam parameters. We also demonstrate that incoherent superposition of two partially coherent sources with different degrees of coherence provides a convenient way for constructing various degrees of coherence of the combined source. Our method and results are useful for beam shaping and particle trapping.

Phase-only devices based on liquid crystals are becoming popular solutions for a high number of applications in many diverse areas. The use of an electrooptic material such as liquid crystals makes the device tunable, opening up many different possibilities of light beam manipulations: beam steering, beam shaping, modulation, focusing, generation of vortices or vector beams, etc. The subject has received a significant boost in the last decade since many research labs working on liquid crystal displays – an area almost entirely transferred to electronic companies – have evolved to these devices, where new effects and applications are continuously being unveiled, and a number of issues affecting their performance are still unsolved. The work is a review of the most relevant kinds of photonic devices developed with this technology. A detailed study of every device and effect would have been too lengthy and possibly would have lacked coherence for dealing on too dissimilar topics. Therefore, the work is focused on passive devices, i.e., with no active matrix driving, thus circumventing the large field of spatial light modulators, which surely deserve a thorough review themselves, but have been already analyzed in many publications.

Low Earth orbit (LEO) satellites operating below 1,400 km are currently in use for various applications, ranging from remote sensing and weather forecast to voice and data communications and scientific research. Because of their shorter distance to Earth, simpler, smaller, and therefore lower-gain antennas with wider angular coverage can be mounted on a LEO satellite to establish the communication link.

We report on the separation of complex inner and outer contours from glass articles with curved surfaces using ultrashort pulsed lasers. To achieve single-pass, full-thickness modifications along the entire substrate a processing optics is presented that allows for beam shaping of non-diffracting beams and, additionally, for aberration compensation of phase distortions occurring at the curved interface. The glass articles finally separated by thermal stress or via selective laser etching meet the demands of the medical industry in terms of micro-debris, surface quality and processing speed.

Bessel and annular laser beams offer intriguing possibilities for material processing. However, current beam shaping methods can be limited in tunability, speed, or parallelization possibilities. Here, we show how ultrasounds in liquids enable generating user-selectable arrays of Gaussian, Bessel-like, or annular beams. By cascading two liquid-filled acoustic cavities, each with a different geometry, light control can be achieved at microsecond time scales. Such an acousto-optic technology is easy to implement in current laser-direct writing workstations, providing an unprecedented ability to tune light fields based on application.

Different wavelength lasers are widely used in ophthalmology for example for selectively heating certain tissues of the eye or unleashing the potential of photoactive pharmaceuticals. The problem with many ophthalmic laser-based treatments such as photodynamic therapy for age-related macular degeneration is that the laser technology is outdated and no longer supported despite the wide clinical use of these therapy modalities. Modulight has developed a configurable cloud-connected ophthalmic laser device that can house any of Modulight’s semiconductor lasers and is wirelessly controlled with an iPad. In addition to novel ophthalmic laser technology, Modulight has also developed a novel beam shaping unit which yields superior beam quality and enables exceptionally large treatment spots eliminating the need for multi-spot treatment for larger lesions.

We report a new optofluidic transmissive wavefront modulator optimized for gravity-neutral performance and miniaturized dimensions. The modulator is optimized for compensating gravity-induced aberrations by simulating its behavior with various design configurations. Miniaturization was achieved by a novel method for liquid filling and sealing of the modulator. Key elements of the new interface are intra-substrate channels fabricated by a selective laser-induced etching process. The modulator has a final thickness of 750 µm and can be operated in any orientation without significant loss of modulation quality.

We experimentally demonstrate phase encoding in SHG with transparent all-dielectric metasurfaces. While a similar task was previously achieved with plasmonic metasurfaces for THG beam shaping, here we obtain three-order-of-magnitude higher generation efficiency without thermal dissipation.