Laser manufacturing of aluminum and titanium alloys is gaining interest in the automotive, aerospace, and defense industries due to its diverse applications. Laser interaction with these alloys involves heating, melting, and evaporation, with evaporation being critical. Selective vaporization of certain elements in multi-element alloys can affect stoichiometry. In-situ monitoring of the ejected plume helps control the product quality. Optical emission spectroscopy (OES) characterizes the plume constituents and provides information about the excited states. Our study uses high-speed imaging (HSI) and OES to monitor the laser interaction process with AlMg5 and Ti6Al4V alloys. OES analysis reveals a higher rate of magnesium evaporation compared with aluminum during the millisecond laser interaction with AlMg5, a trend that intensifies with an increase in laser power and a decrease in speed. On the other hand, the selective evaporation of magnesium in comparison with aluminum during the nanosecond laser interaction with the AlMg5 alloy is negligible, indicating no effect on stoichiometry. During the interaction between the millisecond laser and the Ti6Al4V alloy, titanium is found to evaporate more compared with aluminum, despite the higher boiling point of titanium relative to aluminum. This behavior contrasts with that of the AlMg5 alloy. HSI reveals an increase in spatter and laser-plume interaction with increased laser power and decreased speed during millisecond laser interaction with AlMg5. In-situ monitoring during single-shot millisecond laser interactions is conducted in a controlled manner with and without Ar gas shielding. The detection of oxidation in the absence of shielding gas through OES analysis highlights its potential for process monitoring.
We present a single-oscillator Tm-doped fiber laser emitting 184 W at 1.95 μm with 49.4% slope-efficiency, 0.6 nm FWHM at 1949.6 nm. An M2 factor is 1.3 at 30% of the maximum output power. We used commercially available fiber components and developed splice optimization technique based on beam diameter monitoring. Compact and efficient polymer-based cooling solution is implemented to aim for industry-friendly application.
Laser manufacturing of aluminum and titanium alloys is gaining interest in the automotive, aerospace, and defense industries due to their diverse applications. Laser interaction with these alloys involves heating, melting, and evaporation, with evaporation being critical. Selective vaporization of low-melting-point constituents in multi-element alloys can affect stoichiometry. In-situ monitoring of the ejected plume helps control product quality. Optical Emission Spectroscopy (OES) characterizes plume constituents and provides information about excited states. Our study used high-speed imaging and OES to monitor the laser interaction process with AlMg5 and Ti6Al4V alloys. OES analysis revealed a higher rate of magnesium evaporation compared to aluminum, a trend that intensified with an increase in laser power and a decrease in speed. High-speed imaging revealed an increase in spatter and laser-plume interaction with increased laser power and decreased speed. In-situ monitoring during single-shot laser interactions was conducted in a controlled manner with and without Ar gas shielding. The detection of oxidation in the absence of shielding gas through OES analysis highlights its potential for process monitoring.
Optical array antennas have diverse applications in optical communication, remote sensing, imaging, and astronomy, supporting a broad range of optical and photonics-based technologies. Traditional square phased array antennas require a half-wavelength emitter spacing to prevent secondary orders of emission (aliasing). However, achieving such small distances in optics is impractical. To break this limitation irregularly-placed arrays has been proposed. This study focuses on the alias-free spiral array, which allows for high level of sidelobe suppression. Using standard Huygens–Fresnel principle approach to calculate the emission pattern, we identify key parameters of the spiral and consider their influence on the result. We perform multi-parametric optimisation of the spiral array for maximum suppression of sidelobes, enhancing its performance by dB compared to previously suggested bio-inspired design. This research provides insights into overcoming aliasing challenges and improving the efficiency of optical array antennas.
Self-injection locking is a dynamic process that passively stabilizes the emission frequency of a laser through resonant optical feedback. In the conventional approach, the laser is self-injection locked to a high-Q microresonator via front facet coupling. However, the front facet power of such lasers is limited by nonlinear effects in the microresonator. In this study, we propose an alternative self-injection locking scheme using a back facet-coupled laser, where the power from the back facet is optimally tuned to avoid nonlinear effects in the microresonator. We develop a model for the proposed scheme and find the optimal states of the scheme.
Free space optics propagation through the atmosphere experiences wavefront phase deformation, beam distortion, and aberrations due to the refraction index variations fluctuation along the optical path . Many studies have been done to analyse the atmospheric layers and understand their effects on beam quality. Different applications need to tackle the atmospheric effect like satellite to ground optical communication, astronomy, beam sensing, and power beaming where the atmospheric effect leads to beam wandering that result on beam mis-pointing and power loss at the receiver/target. This paper covers the design of an atmospheric turbulence generator and its characterization and capabilities to create different atmospheric turbulent strength levels. Temperature variation, wind speed/direction, and humidity effects are considered and monitored to emulate different turbulences regimes (corresponding to different spatial coherence levels) that will impact a Gaussian wavefront beam with different turbulence strengths. The turbulence emulator has various apertures for the incoming beam, outcoming beam, ambient air flow, and tuneable temperature air flow. The mixture of these two airflows results in high-speed refractive index fluctuations. A 1064 nm collimated optical beam is used to characterize the turbulence generator and illustrate the impact of the environmental condition on the outcoming optical beam.
The atmospheric effects on the propagation of light have been a matter of interest in fields like astronomy, meteorology, and optical communications where phase variations of wavefront have a significant impact in detection systems. The effects of the optical turbulence on the laser beam change from one region to another, this is linked to the atmospheric characteristics of the area (relative humidity, atmospheric pressure, wind, and temperature). Our research center is in a region with harsh atmospheric conditions for optical propagation. For this reason, it is important to measure and replicate these conditions in the laboratory environment. In this work, we present the results of our laboratory experimental setup to characterize infrared beam at 1064-nm using a turbulence chamber designed by our team. In our experimental setup, the transversal windspeed is varied in the turbulence generator chamber, and the beam centroid is measured after 4-m propagation path for different wavelengths and different optical powers. The beam is analyzed before and after the turbulence generation chamber. In this paper, we report our initial results in developing a laboratory experimental setup to emulate Middle East atmospheric conditions and compensate for these effects using an adaptive optics system.
In this paper, the simulation of a 2-kW laser demonstrator using a free-space incoherent beam combining based on two laser diodes stacks at 980 nm is presented. The implementation of the simulations is done in Optic Studio Zemax software. The goal of this work is to design and validate the feasibility of the construction of an experimental laser demonstrator in a laboratory for rapid prototyping of high-power laser sources. The simulation results are characterized using power density at a detector, beam parameter product, and spot size as descriptors.
Laser propagation through a medium is often accurately explained by geometrical optics where light is described as rays. When considering wave diffraction, a more generalized description of physical optics is used. Faced with the complexity of interactions of a laser beam with the atmosphere, and the additional challenges of deploying a physical high power laser system for advanced evaluation in harsh environment, the use of simulation software is preferred to study and predict the behavior of the beam propagation in atmosphere. In this paper, we show that the intensity and diffraction of a laser beam in the atmosphere can be properly described by geometrical optics when coupled with an appropriate model of the variations of the index of refraction, heat convection velocity, and atmospheric relative humidity. The study uses a Near Infrared (NIR) laser source at 980 nm of 1 kW average power. The laser beam propagation was implemented using a finite element model developed with a COMSOL multi-physics ray tracing model in both transient and steady-state regimes. The beam divergence from the center of the propagation path was clearly observed when the crosswind velocity inside the domain was greater than 10 m/s while having 300K temperature at 1 atm pressure as initial conditions. The direction and amount of divergence are observed to be directly linked to the velocity of the cross-wind, as well as the refractive index variations due to the amount of humidity in the air, and the heat generated by the laser beam in the atmosphere. According to our results, the higher the humidity of the air is, the more energy is deposited in the atmosphere resulting in the reduction of the accumulated power on the target.
The atmospheric propagation of Near Infrared (NIR) high-power laser beams is affected by the thermal interactions of the electromagnetic beam with the air and the phase perturbations caused by the air inhomogeneities. These interactions lead to inefficient delivery of energy to far field surface. In this work, the implementation of a simulation model integrating thermal distortions induced by the laser beam and the turbulence of atmosphere is presented. Additionally, an iterative learning method is integrated in the simulator to correct the laser beam profile using a deformable mirror. Simulations are realized for a 1.5 kW laser beam at 1064 nm propagating along 150 m propagation path.
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