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.
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.
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.
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.
As major milestone of commissioning phase of beam transport section for the 10 PetaWatts beamlines of Extreme Light Infrastructure Nuclear Physics (ELI-NP) located in Magurele (Romania), we have propagated the beam throughout the beam transport section and measured its energy as well as its pulse duration after compression at full energy and full aperture. 10 consecutive laser pulses have been shot at a repetition rate of 1 shot per minute with compressed pulse energy ranging between 241 and 246 Joules while pulse duration has been measured at 23 fs leading to the first ever operation above 10 PetaWatts peak power
We report the generation of unprecedented 10 PetaWatt laser pulses obtained from each of the two beamlines of the High Power Laser System (HPLS) of ELI-NP (Extreme Light Infrastructure – Nuclear Physics) research infrastructure. The laser system is a hybrid system made of a double CPA based on amplification within Titanium Sapphire crystals combined with an OPCPA with a parametric amplification stage boosting the energy to 10 mJ at the entrance of the second CPA. A XPW filter is also inserted between the two CPA and in combination with the OPCPA improves the temporal contrast of the pulses by typically 7 orders of magnitude. The spectral effects occurring during amplification such as gain narrowing and wavelength shifting are compensated through the use of spectral filters. Final amplification stages are involving large aperture Ti:Sapphire crystals (up to 200 mm) which are pumped by high energy frequencydoubled Nd:Glass lasers delivering each 100 J of green light. Laser beams have been amplified respectively up to 332 J and to 342 J of pulse energy at 1 shot per minute without any occurrence of ASE and transverse lasing thanks to index matching fluid surrounding the crystal over is entire length and pump deposition management over the time before each beam pass within the Ti:Sapphire crystal. We have demonstrated full aperture compression by metric gratings of these amplified pulses down to 22.6 fs and therefore made the full demonstration for the first time ever of 10 PW capability from a laser system.
The development of coherent light sources with emission in the mid-IR is currently undergoing a remarkable revolution. The mid-IR spectral range has always been of tremendous interest, mainly to spectroscopists, due to the ability of mid-IR light to access rotational and vibrational resonances of molecules which give rise to superb sensitivity upon optical probing [1-3]. Previously, high energy resolution was achieved with narrowband lasers or parametric sources, but the advent of frequency comb sources has revolutionized spectroscopy by providing high energy resolution within the frequency comb structure of the spectrum and at the same time broadband coverage and short pulse duration [4-6]. Such carrier to envelope phase (CEP) controlled light waveforms, when achieved at ultrahigh intensity, give rise to extreme effects such as the generation of isolated attosecond pulses in the vacuum to extreme ultraviolet range (XUV) [7]. Motivated largely by the vast potential of attosecond science, the development of ultraintense few-cycle and CEP stable sources has intensified [8], and it was recognized that coherent soft X-ray radiation could be generated when driving high harmonic generation (HHG) with long wavelength sources [9-11]. Recently, based on this concept, the highest waveform controlled soft X-ray flux [12] and isolated attosecond pulse emission at 300 eV [13] was demonstrated via HHG from a 1850 nm, sub-2-cycle source [14]. Within strong field physics, long wavelength scaling may lead to further interesting physics such as the direct reshaping of the carrier field [15], scaling of quantum path dynamics [16], the breakdown of the dipole approximation [17] or direct laser acceleration [18]. The experimental development of long wavelength light sources therefore holds great promise in many fields of science and will lead to numerous applications beyond strong field physics and attosecond science.
In this paper, we present results about a high energy picosecond Holmium YLF laser developed in order to be used as the puming laser for the first mid-IR optical parametric chirped pulse amplifier (OPCPA) operating at a center wavelength of 7 μm with output parameters suitable already for strong-field experiments. It is also the first demonstration of an Optical Parametric Chirped Pulse Amplifier (OPCPA) using a 2 μm laser pump source which enables the use of nonoxide nonlinear crystals with typically limited transparency at 1 mm wavelength. This new OPCPA system is alloptically synchronized and generates 0.2 mJ energy, CEP stable optical pulses. The pulses are currently compressed to sub-8 optical cycles but support a sub-4 cycle pulse duration. The discrepancy in compression is due to uncompensated higher order phase from the grating compressor which will be addressed in the future.
A laser system made of two beams of 10 PW each has been designed and is currently built for ELI-NP research infrastructure. Design is presented as well as preliminary results up to the 1PW level amplifier.
O. Chalus, A. Pellegrina, S. Ricaud, O. Casagrande, C. Derycke, C. Radier, A. Soujaeff, G. Matras, G. Rey, L. Boudjemaa, C. Simon-Boisson, S. Laux, F. Lureau
A hybrid Ti:Sa CPA/BBO OPCPA system with a XPW filter in between the two has been developed to produce a broadband high contrast seeder of 10 mJ for the two 10 PetaWatt beamlines of ELI NP infrastructure.
We demonstrate operation of a simple and reliable water-cooled femtosecond laser running at 10 kHz
suitable for industrial micromachining applications. A laser geometry involving only a regenerative
amplifier and delivering 3.5 W average power 60-fs pulses is compared to a more conventional
architecture using an additional multi-pass amplifier. Both laser systems require a moderate pumping
laser of ~30 W average power and deliver high-quality beams (M2<1.2).
PACS : 42.55-f ; 42.60 v; 42.60 Rn
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