Optical Laser Beam Research Articles

Femtosecond optical vortex-induced flower-shaped surface relief structures in an azo-polymer film

We study the formation of surface relief structures in azo-polymers generated via two-photon induced photoisomerization using a femtosecond near-infrared optical vortex laser beam. These structures exhibit exotic flower-like shapes with petals along the azimuthal direction, and they are formed from spatial mode instability, which is associated with third-order nonlinear effects in the azo-polymer. This process is a unique and exotic interaction between light and matter, which may be applied to the development of advanced optical data storage technologies. Here, an additional degree of freedom is offered by the number of formed petals, which themselves are a function of the topological charge of the optical vortex beam.

Generating Optical Vortex Array Laser Beams of Superimposing Hermite–Gaussian Beams with a Dual–Phase Modulation Digital Laser System

This study presents an efficient and practical intra-cavity approach for selectively generating vortex array laser beams employing a dual-phase modulation digital laser system, which has not yet been completed in single-phase modulation digital laser. The stable optical vortex array laser beams were formed by superimposing cavity Hermite–Gaussian (HG) eigenmodes. In particular, when the selected cavity HG modes shared the same Gouy phase, the resulting optical vortex beam could preserve its light field pattern, thereby maintaining the optical vortex properties in the near and far fields. Numerical results demonstrated that employing dual-phase modulation could establish optimal boundary conditions for the selection of HG modes within the cavity, successfully generating various vortex array laser beams. The experimental validation of the proposed method confirmed the ability to select optical vortex array lasers solely by controlling the loaded phase of the dual-phase modulation digital laser. These results demonstrate the ability of digital lasers to generate and dynamically control optical vortex array lasers.

Manipulating optical absorption and polarization using microwave control in an atomic vapor

The multiplicity of atomic states (and the transitions between them) offer an innate, coherent platform through which microwave and optical fields effectively interact. In an atomic vapor near room temperature, we combine optical and microwave fields to generate a macroscopic internal angular momentum among the atoms—an atomic polarization—at an arbitrary angle with respect to the optical (laser) beam. This geometric freedom enables microwave control over photonic degrees of freedom, which we use in two demonstrations: using microwave-assisted optical pumping, we can rotate linear polarization through several degrees, and we can control the absorption for specific transitions and polarizations, which has applications for microwave-to-optical transduction.

Searching for axion resonances in vacuum birefringence with three-beam collisions

We consider birefringent (i.e., polarization changing) scattering of x-ray photons at the superposition of two optical laser beams of ultrahigh intensity and study the resonant contributions of axions or axionlike particles, which could also be short lived. Applying the specifications of the Helmholtz International Beamline for Extreme Fields (HIBEF), we find that this setup can be more sensitive than previous light-by-light scattering (birefringence) or light-shining-through-wall experiments in a certain domain of parameter space. By changing the pump and probe laser orientations and frequencies, one can even scan different axion masses, i.e., chart the axion propagator. Published by the American Physical Society 2024

Optical Phased Array-Based Laser Beam Array Subdivide Pixel Method for Improving Three-Dimensional Imaging Resolution

The small number of pixels in the current linear mode avalanche photodiode (LM-APD) array limits its three-dimensional (3D) imaging resolution. We use an optical phased array-based beam array subdivided pixel method to improve the 3D imaging resolution, using an optical phased array to generate a beam array with the same number of pixels as the LM-APD array and matching positions and controlling each sub-beam in the beam array to scan in the field of view of the corresponding pixel. The sub-beam divergence angle in the beam array is smaller than the instantaneous field of view angle of a single pixel in the LM-APD array. The sub-beam scanning in a single pixel’s field of view realizes the multiple acquisition of the target 3D information by the LM-APD array, thus improving the resolution of the LM-APD array. The distribution of the beam array in the far field is simulated, and the main performance parameters of 3D imaging are analyzed. Finally, a liquid crystal phase modulator is used as an optical phased array device to conduct experiments on a target 20 m away, and the results prove that our method can improve the resolution from 4 × 4 to 8 × 8, which can be improved at least four times.

Laser heating of ferroelectric cubes for tunable electromagnetic properties in metamaterials

In this experimental study, we demonstrate the feasibility of a thermally tunable, resonant dielectric microwave metasurface based on sub-wavelength Mie resonances of ferroelectric dielectric cubes (Calcium titanate, CaTiO3) in which the temperature of the meta-atoms can be locally and dynamically controlled by heating with an optical laser beam over a large range of temperatures and, consequently, values of the dielectric constant of the cube and corresponding resonance frequency of the meta-atoms. This avoids any interference of otherwise necessary heating elements or power supply wires with the propagation of the microwave signal and can be made spatially addressable. The concept scales at least to the THz domain. This contactless approach opens up an alternative avenue to tunability and active control of metamaterials.

Chiral crystallization manipulated by orbital angular momentum of light

We present what we believe to be the demonstration of optical vortex trapping and chiral crystallization of sodium chlorate (NaClO3). In this work, the chirality of NaClO3 crystals is selectively controlled by altering the helicity (helical direction of the wavefront) of an irradiating optical vortex laser beam. A high crystal enantiomeric excess of 57% is achieved. These results demonstrate that the orbital angular momentum of an irradiating optical vortex laser beam twists the crystal during its polymorphic transition from a metastable achiral crystal to a stable chiral crystal. This work will offer fundamental insights into the dynamics and mechanism of enantioselective control in chiral crystallization and the origin of homochirality.

Direction-independent laser-GMA hybrid welding with coaxial wire feed and annular beam

Conventional laser gas metal arc hybrid welding (LB-GMA hybrid welding) is used as an efficient joining process in several high-tech steel processing production facilities. However, the use of the LB-GMA hybrid welding is often limited to the joining of linear weld seams as the welding process has a preferred welding direction due to lateral positioning of the laser beam and welding wire electrode. Reorienting the welding direction, therefore, often results in weld defects since changing the welding direction also requires a geometric manipulation of the GMA torch in relation to the laser beam optics. This means a considerable additional effort that is necessary if this efficient welding process is to be used for geometrically complex weld seam contours. Furthermore, the conventional LB-GMA hybrid welding process has a high adjustment complexity. Within this work, a direction-independent laser GMA hybrid welding head with an annular beam and coaxial wire feed is used. The annular laser beam with homogenous intensity profile is formed by a special processing head, split and reassembled around the coaxial wire. Due to the coaxial arrangement of the wire electrode to the annular beam, the hybrid process is in theory direction independent. As a result, there should not be any irregularities in the weld seam, when the welding direction is changed. The annular beam considerably reduces the complexity of adjustment and improves reproducibility. The focus of this work is to qualify the process for joining geometrically complex weld contours and to investigate possible advantages of the directional independence of the coaxial LB-GMA hybrid welding process. For this purpose, fillet welds in lap joint configuration with a sheet thickness of 2 mm each at different weld contours (different direction changes, corners, radii) are discussed. By performing a DoE-based sensitivity analysis, influencing factors on the quality of the generated weld are analysed.

Investigating pair-production by Breit–Wheeler process in a collisional plasma

Positrons have many potential applications in the field of high-energy nuclear and particle physics. For the generation of such high-energy positrons, we propose a mechanism via an interaction of optical vortex laser beams with collisional plasma. Based on the multiphoton Breit–Wheeler mechanism, the production of electron–positron pairs shows to be strongly dependent on the energy associated with the synchrotron radiation. Such radiations are emitted by accelerated charged particles in the plasma channel under quasistatic spontaneous magnetic field that confines the motion of the electrons. For the precise regulation of the accelerated positrons important quantities such as the probabilistic generation of positrons and the angular momentum of the plasma electrons are evaluated and discussed. It is observed that the use of the incident Laguerre–Gaussian laser beam helps to generate on-axis sheath formation to focus and accelerate the produced positrons.

A High-Speed Chip-Scale Rotary Polygon Optical Scanner Based on a Micromotor Integrated With a Micro-Polyhedron Mirror

Micro-opto-electro-mechanical systems (MOEMS) based mirrors with a suitable actuation range are often used for optical beam scanning applications. While several MOEMS scanners have been reported, they often have limitations with respect to their range of motion, field of view, mass, size and fabrication cost. In this work, we present a rotary micro-polygon scanner based on an electrostatic variable capacitance micromotor for laser beam steering applications. The miniaturized scanner consists of a hollow micro-polyhedron mirror with a base radius of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200 {\mu }\text{m}$ </tex-math></inline-formula> and a height of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$400 {\mu }\text{m}$ </tex-math></inline-formula> . It is mounted on the rotor of a variable capacitance micromotor using an epoxy-based adhesive. The rotor has a diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$600 {\mu }\text{m}$ </tex-math></inline-formula> and is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.5 {\mu }\text{m}$ </tex-math></inline-formula> thick. The micromotor was fabricated using a commercial three-layer polysilicon surface micro-machining process (PolyMUMPs) and the micro-polyhedrons were fabricated using a commercial bulk micro-machining process (PiezeoMUMPs). After fabrication of the components, the micro-scanner was assembled and operated under atmospheric conditions using a three-phase square wave excitation ranging from 0 V to 200 V and achieved rotational speeds of up to 2100 rpm. An optical laser beam with a wavelength of 632 nm was reflected off the sidewall of the rotating micro-polyhedron, achieving an experimentally measured scanning angular range of 57.88°, an angular scan rate of 220 radians per second and a scan speed of 25,200 lines per minute or 420 lines per second with a 12 sided micro-mirror. The ratio of the output power over the input optical power is measured over a scanning range of 22°, which is limited by the size of the photo-detector, yielding a ratio spanning from 0.18 to 0.22. This rotary micro-scanner can provide high scanning speeds and a wide scanning field of view with a footprint of 1.25 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and a thickness of 0.83 mm, which is suitable to implement chip-level high-performance micro-beam steering systems for various applications. [2022-0020]

Generation of hexagonal close-packed ring-shaped structures using an optical vortex

Abstract An optical vortex possesses a ring-shaped spatial profile and orbital angular momentum (OAM) owing to its helical wavefront. This form of structured light has garnered significant attention in recent years, and it has enabled new investigations in fundamental physics and applications. One such exciting application is laser-based material transfer for nano-/micro-fabrication. In this work, we demonstrate the application of a single-pulse optical vortex laser beam for direct printing of ring-shaped structures composed of hexagonal close-packed, mono-/multi-layered nanoparticles which exhibit ‘structural color’. We compare and contrast the interaction of the vortex beam with both dielectric and metallic nanoparticles and offer physical insight into how the OAM of vortex beams interacts with matter. The demonstrated technique holds promise for not only photonic-based nano-/micro-fabrication, but also as a means of sorting particles on the nanoscale, a technology which we term ‘optical vortex nanoparticle sorting’.

Characterization of laser beams: theory and application in laser-assisted bonding process

The International Organization for Standardization (ISO), in collaboration with the academic community, has developed and published a comprehensive system of standards for the characterization of optical components and laser beams. Our study offers a pedagogical introduction to the theory and application of laser beam characterization in accordance with ISO 13694:2018 and ISO 11145:2018. The characterizing parameters of each ISO standard are presented, defined mathematically, and explained in detail through the use of a minimum working example. A laser beam applied to an actual industrial process [laser-assisted bonding (LAB) process in the semiconductor packaging industry] is thoroughly analyzed to help the reader understand and interpret the characterizing results. Background noise correction and unit conversion methods are also discussed. We target researchers new to the field of laser beam analysis who want the acquire background knowledge, as well as more experienced researchers who want to implement their own laser beam analysis software and propose new definitions for their specific application. Although our study deals with only two ISO standards, the methods covered in our study can be easily applied to other norms that fit the reader’s application. Our study should not be treated as a full review of the LAB process nor of the beam profiling instruments and measurement principles. These are only mentioned to enhance the reader’s learning experience.

Alternative method of generating gamma rays with orbital angular momentum

We study an alternative method of generating gamma rays with orbital angular momentum (OAM). Accelerated partially-stripped ions are used as an energy up-converter. Irradiating an optical laser beam with OAM on ultrarelativistic ions, they are excited to a state of large angular momentum. Gamma rays with OAM are emitted in their deexcitation process. We examine the excitation cross-section and deexcitation rate.

Performance investigation of a 3.84 Tb/s WDM-based FSO transmission system incorporating 3-D orthogonal modulation scheme

The present work discusses the development and simulative investigation of a high-capacity wavelength division multiplexed free space optics (FSO) transmission system. A novel 3-D orthogonal modulation scheme is proposed, which simultaneously capitalizes on different signal properties of an optical laser beam, i.e., intensity, phase, and state of polarization to transmit three independent 40 Gb/s data streams on a single optical carrier signal, realizing a net 120 Gb/s transmission rate per wavelength channel. 32 such independent wavelength channels are multiplexed in the proposed FSO system and its performance is numerically investigated over different climate conditions with respect to range, Quality factor, bit error rate, and eye diagrams of the information signal using Optisystem simulation software. Through numerical simulations, we report faithful 3.84 Tb/s transmission over free space channel with maximum link range varying from 1.6 to 40 km depending on the external climate conditions.

Influence of Laser Beam Profiles on the Performance of Laser‐Driven Flyers

AbstractIn order to reveal the influence of laser beam profiles on the performance of laser‐driven flyers, three different laser beam profiles including original laser beam, reshaped laser beam and optical fiber output laser beam were used to launch the flyer plates. The original laser beam showed plenty of “hot spots”. A lenslet array was used to reshape the original laser beam and a much smoother intensity distribution was obtained. Both original and reshaped laser beams were coupled to optical fibers. Results showed that the laser energy that a fiber can reliably transmit increased 29 % and reached up to 59 mJ by reshaping the original laser beam. Furthermore, PDV measurements indicated that there was a 68 % increase in flyer velocity when the flyer was driven by a fiber coupled laser instead of the original laser, and the flyer velocity could reach up to 1.5 km/s when irradiated by a 50 mJ laser. Aside from the velocity increase, the fiber coupled laser was proven to be capable of producing controllable planar and intact flyer. A fiber coupled laser initiation system incorporating a laser slapper detonator was developed. The fine grain CL‐20 was successfully initiated using the fiber coupled laser initiation system under 40 mJ laser energy, implicating the fiber coupled system is applicable in high energy explosive initiations.

Experimental investigations on the bubbly wake of a transom stern model using optical laser beam scattering characteristics

In this paper a new procedure for detection and quantification of the main features of ship models bubbly wake is presented. The method is based on light scattering characteristics of laser beams passing through the wake of ship models. An optical light scattering model is developed and validated in a series of steady bubbly flow tests in a water tank, with time-invariant mean multiphase flow properties. Then a series of unsteady tests are conducted in a towing tank so as to study bubbly wake properties of a transom stern model. Temporal wake strength and its final detection time and length are measured using light scattering measurements. Light scattering analysis provides longitudinal, lateral, and vertical distributions of the wake without any flow intrusion. Also by combining the experimental and analytical results, a complementary assay for determination of average bubble size and bubble number density distribution is presented. Effects of model velocity on the bubbly wake features of the transom stern are also investigated using the suggested procedures. Results indicate that increasing the model velocity increases the total bubbly wake length and lifetime. Details of the wake lateral distribution reveal the prominent contribution of transom stern diverging waves on the bubbly wake air entrainment.

Omnidirectional Optical Crosslinks for CubeSats: Transmitter Optimization.

CubeSat swarm in LEO orbit is an attractive alternative to present-day expensive and bulky satellite-based remote sensing systems. This paper presents the design and optimization rules to achieve omnidirectional, high speed, long-range (more than 100 km) data communication among CubeSats. The unprecedented size, weight, power, and cost constraints imposed by the CubeSat platform and the availability of the commercial-off-the-shelf components are considered in the analyses. Analytical studies related to the scanning mirror-based beam steering system as well as scanning mirror's smallest step angle requirement are presented. In addition, we demonstrate the relations and dependencies among scanning mirror's smallest step angle, laser beam divergence, optics dimensions, communication distance, and scanning area filling efficiency, etc. Furthermore, the optimization challenges of the transmit laser beam size considering the interplay among beam divergence, beam clipping, and scattering are studied in detail. This paper also presents the effect of laser peak power, initial beam size, and communication distance on effective communication beam width to maintain a long-distance (more than 100 km) communication with SNR ≥ 10 dB at a data rate greater than 500 Mb/s.

Investigation of optical laser beam impairment on hypergolic lunarlander exhaust plumes for a lidar feasibility study

Plumes of two hypergolic bipropellant thrusters of a LunarLander application, developed by ArianeGroup® Lampoldshausen, were optically examined regarding their potential to interfere with laser beams of a nearby LIDAR system. On one hand, hot exhaust gas of a 22 N Vernier thruster was used to investigate the scattering of a λ = 632.8 nm HeNe laser beam. A series of several engine pulse modes were conducted. An obvious correlation between engine pulse duration and backscattered light intensity is revealed. The shortest pulses result in the most intense backscattering, indicating an incomplete combustion process between the hypergolic constituents MMH = monomethylhydrazine and NTO = (di)nitrogen tetroxide for very short pulse lengths. On the other hand, a prolonged pulse mode of 120 ms firing time causes only marginal deflection of the laser beam. Furthermore, steady operation leads to a negligible signal of backscattered photons, accompanied by increasing emission bands of combustion products such as CN, O2, and CO2. However, the disappearance of the OH* emission band, typical for this hypergolic combustion, shows a nearly complete reaction of the hydroxyl radical within the combustor for all pulse modes. Mie scattering calculations show a correlation between the incident laser beam wavelength and the backscattered light intensity. On the other hand, near infrared spectroscopy on the exhaust plume of a 500 N apogee thruster revealed that interfering flame emission and absorption in the optical range around λ = 1064 nm can be neglected. The relatively intense flame emission measured for λ ≥ 1300 nm, on the other hand, is a potential risk for the application of a laser beam of a similar wavelength.

Vector dissipative light bullets in optical laser beam

The dynamics of light bullets propagating in nonlinear media with linear/nonlinear, gain/loss and coupling described by the (2+1)-dimensional vectorial cubic–quintic complex Ginzburg–Landau (CGL) equations is considered. The evolution and the stability of the vector dissipative optical light bullets, generated from an asymmetric input with respect to two transverse coordinates x and y, are studied. We use the variational method to find a set of differential equations characterizing the variation of the light bullet parameters in the laser cavity. This approach allows us to analyze the influence of various physical parameters on the dynamics of the propagating beam and its relevant parameters. Then, we solve the original coupled (2+1)D cubic–quintic CGL equation using the split-step Fourier method. Numerical results and analytical predictions are confronted, and a good agreement between the two approaches is obtained.

Fan-shaped optical laser beams blow away impurities

Researchers create a fan-shaped vortex beam that can perform optical clearing, optical shielding and optical transporting.