An all-optical passive device based on wavelength-adaptive diffractive neural network for dynamic beam shaping

Dynamic phase-only beam shaping with a liquid crystal spatial light modulator is a powerful technique for tailoring the intensity profile or wave front of a beam. While shaping and controlling the light field is a highly researched topic, dynamic nonlinear beam shaping has hardly been explored so far. One potential reason is that generating the second harmonic is a degenerate process as it mixes two fields at the same frequency. To overcome this problem, we propose the use of type II phase matching as a control mechanism to distinguish between the two fields. Our experiments demonstrate that distributions of arbitrary intensity can be shaped in the frequency-converted field at the same quality as for linear beam shaping and with conversion efficiencies similar to without beam shaping. We envision this method as a milestone toward beam shaping beyond the physical limits of liquid crystal displays by facilitating dynamic phase-only beam shaping in the ultraviolet spectral range.

Since the power of continuous wave laser sources have reached one kilowatt, beam shaping is an important topic in the sector of laser material processing. The high intensity allows the increase of process speed, but the extreme local overheating often decreases the quality. Typically beam shaping solutions use a static beam adaptation by optical elements. For laser cutting for example, the increase of sheet thickness requires larger Rayleigh length what will be achieved by adapting the conditions of the incident ray at the focalization element. In this case the cutting quality increases but the cutting speed decreases. The advantage of high intensity gets lost. The dynamic beam shaping is known from the electron beam, and already applied in laser hardening and welding applications using galvanometer scanners. While the galvo-systems reached the physical limitations, the frequency is not high enough to achieve the desired effects. Resonance galvanometer scanners are limited by the atmosphere damping, too.This paper will introduce a new possibility of dynamic beam shaping, using MEMS technology in a low pressure atmosphere. It describes the reached steps to transfer the technology from display and sensor applications with low apertures and laser power to laser material applications with large apertures and high laser power. Finally, the technology possibilities are disclosed for the complete field of laser application.Since the power of continuous wave laser sources have reached one kilowatt, beam shaping is an important topic in the sector of laser material processing. The high intensity allows the increase of process speed, but the extreme local overheating often decreases the quality. Typically beam shaping solutions use a static beam adaptation by optical elements. For laser cutting for example, the increase of sheet thickness requires larger Rayleigh length what will be achieved by adapting the conditions of the incident ray at the focalization element. In this case the cutting quality increases but the cutting speed decreases. The advantage of high intensity gets lost. The dynamic beam shaping is known from the electron beam, and already applied in laser hardening and welding applications using galvanometer scanners. While the galvo-systems reached the physical limitations, the frequency is not high enough to achieve the desired effects. Resonance galvanometer scanners are limited by the atmosphere damping, too.T...

An optically addressable light valve is used for high repetition rate dynamic laser beam shaping used in a unique metal additive manufacturing process [1]. The resulting Area Printing™ delivers high power pulses - each with an individually controlled shape - to a metal powder bed that locally sinters and melts to consolidate into a fully dense metal part. This technology and device enable scaling cheaper additive manufacturing with high spatial resolution, while capable of printing part features beyond reach of conventional manufacturing, and with greater efficiency and minimal spatter defects. We address here the unique optoelectronic properties needed from the optically addressable photoresistor that controls the dynamic beam shaping for high density, high-resolution laser 3D printing. Further description is presented of the device-level thermomechanical analysis from parasitic absorption of the laser at kW to MW power levels. We thus highlight key areas of semiconductor properties challenging the performance capabilities in optically addressed light valves used in high power switching applications. [1] https://www.seurat.com/area-printing

Laser beam welding of hot crack sensitive Al-alloys without filler wire by intensity controlled dynamic beam oscillation

This review examines the state-of-the-art in spatial manipulation of ultrafast laser processing using dynamic light modulators, with a particular focus on liquid crystal-based systems. We discuss phase modulation strategies and highlight the current limitations and challenges in surface and bulk processing. Specifically, we emphasize the delicate balance between high-fidelity beam shaping and energy efficiency, both critical for surface and bulk processing applications. Given the inherent physical limitations of spatial light modulators such as spatial resolution, fill factor, and phase modulation range. We explore techniques developed to bridge the gap between desired intensity distributions and actual experimental beam profiles. We present various laser light modulation technologies and the main algorithmic strategies for obtaining modulation patterns. The paper includes application examples across a wide range of fields, from surgery to surface structuring, cutting, bulk photo-inscription of optical functions, and additive manufacturing, highlighting the significant enhancements in processing speed and precision due to spatial beam shaping. The diverse applications and the technological limitations underscore the need for adapted modulation pattern calculation methods. We discuss several advancements addressing these challenges, involving both experimental and algorithmic developments, including the recent incorporation of artificial intelligence. Additionally, we cover recent progress in phase and pulse front control based on spatial modulators, which introduces an extra control parameter for light excitation with high potential for achieving more controlled processing outcomes.

Controlling microbial adhesion in industrial and healthcare settings is crucial for maintaining hygiene and preventing biofilm formation. This work describes a novel method to efficiently produce yeast adhesion-reducing surfaces using dynamic beam-shaping with a spatial light modulator. At first, the laser-induced periodic surface structures (LIPSS) topography was tuned to test microbial adherence in a variety of LIPSS configurations, specifically using Saccharomyces cerevisiae as a model organism. A novel and robust dual-pass laser strategy was implemented to create hierarchical LIPSS structures with periodicities of 630 nm and 5 μm. The integration of dynamic beam shaping with spatial light modulator (SLM) significantly enhanced production efficiency, achieving a throughput of up to 150 cm 2 /min. The laser-structured surfaces exhibited a significant reduction in yeast adhesion, with a decrease of 95% in adherent cells and achieving a maximum reduction of 99.88%. These findings offer promising implications for developing advanced surface treatments to improve hygiene in industries such as food processing and healthcare, where minimizing microbial colonization is vital.

Laser-based metal manufacturing techniques, such as laser welding and additive manufacturing, offer high precision and versatility, but the complex melting and resolidification processes often lead to uneven surface morphologies. This study investigates the effects of dynamically modulated bimodal beam shaping on metal surface topography. Two independently controlled Gaussian beams were super-positioned, with one beam oscillating sinusoidally to modulate the bimodal intensity profile both spatially and temporally during laser processing. At low oscillation frequencies, periodic surface features emerged, whereas high modulation frequencies produced smooth melt tracks. Simulations indicate that higher frequencies promote a more uniform spatial energy distribution and reduce melt durations. These results highlight the potential of tuning dynamic bimodal beam shaping parameters to actively control and suppress unwanted surface features, offering a framework for improving surface quality in laser-based manufacturing processes.

We present an indoor free space, line-of-sight optical communication system with gigabit bandwidth using an ultra-low power VCSEL diode, which is enhanced by dynamic beam steering and beam shaping for rapid user acquisition.

This paper presents a sequential linear least square algorithm for tracking dynamic shapes of piezoelectric smart structures. The dynamic shape discussed in this paper is defined as a host structural shape varying with time, and the tracking technique is to find an electric voltage history for each piezoelectric device over a time period so that the desired structural movements can be achieved. In the theoretical formulation, dynamic equations of piezoelectric smart structures are introduced by finite element analysis, and then a solution procedure for a set of time-dependent electric voltages is derived by combining the linear least square method and the Houbolt numerical integration scheme. The formulation indicates that this algorithm can be used to find the time-dependent voltages for tracking structural movements of piezoelectric smart structures. The present novel formulation is then demonstrated through numerical examples for tracking dynamic shapes of piezoelectric smart beams and plates. The numerical results for the smart beam are compared with the experimental ones. It is shown that the present sequential linear least square algorithm is capable of efficiently simulating dynamic shape tracking for smart structures. Copyright © 2006 John Wiley & Sons, Ltd.

In this work we demonstrate optical trapping and manipulation of microparticles suspended in water due to laser-induced convection currents. Convection currents are generated due to laser light absorption in an hydrogenated amorphous silicon (a:Si-H) thin film. The particles are dragged towards the beam's center by the convection currents (Stokes drag force) allowing trapping with powers as low as 0.8 mW. However, for powers >3 mW trapped particles form a ring around the beam due to two competing forces: Stokes drag and thermo-photophoretic forces. Additionally, we show that dynamic beam shaping can be used to trap and manipulate multiple particles by photophotophoresis without the need of lithographically created resistive heaters.

There have been numerous efforts to use fiber-optic techniques in array antennas. Fiber-optics is attractive for the same reasons it is the technology of choice for telecommunications applications. Advantages include: a natural resistance to electromagnetic interference (EMI), low weight, small size, low intrinsic losses and the ability to easily remote components. Additionally, its unique processing capabilities permit simplifying the arrays and adding system functionality, e.g., dynamic beam shaping (adaptive beamforming) and time-steering. A wide variety of optical implementations have been proposed for time-steered array antennas. The Naval Research Laboratory (NRL) has developed a practical, fiber optic technique for implementing time-steered arrays. The approach is based upon a dispersive, fiber-optic delay line combined with a simplified beamforming architecture. This method solves many of the problems associated with optical true time delay (TTD) beamformers. It has been dubbed the fiber-optic dispersive prism. The basis for the approach is shown.

Space-time modulated structures enable advanced wave control by dynamically varying material properties in both space and time. These systems could unlock novel wave phenomena, including nonreciprocal propagation, pulse shaping, and broadband amplification. They also offer new methods for structured light manipulation, such as dynamic beam shaping and space-time wave packets. Beyond wave control, time modulation enables highly parallelized photonic computing and efficient optical information processing. Additionally, isospectrality in space-time metamaterials provides new avenues for optical mode management and high-capacity communication. In this work, we discuss these emerging possibilities and their impact on future photonic technologies.

The largest (up to 64×64) optical phased arrays to date are demonstrated with silicon photonics, including passive arrays generating intricate far-field patterns and an active array for dynamic beam steering and shaping.

Comprehensive benchmarking of laser welding technologies including novel beam shapes and wavelengths for e-drive copper hairpins

A dynamic beam shaping system requires a variable beam expander. Three optical lenses form the core of the proposed beam expander, and two hollow ultrasonic motors are used to adjust the positions of two of the lenses. A polymer-based stator is introduced in the ultrasonic motors to decrease their weight, whereupon a prototype is machined and its performance is assessed. The beam expander starts and stops within 0.05 s, and the minimum positioning error is 0.03 µm by adjusting the motor speed. The presented expander can continuously expand a laser beam by between threefold and fivefold, and nanoscale positioning and high-precision beam shaping are realized by using ultrasonic motors as its actuators.