High-energy Laser Pulses Research Articles

Phase retrieval algorithm applied to high-energy ultrafast lasers.

A standardized phase retrieval algorithm is presented and applied to an industry-grade high-energy ultrashort pulsed laser to uncover its spatial phase distribution. We describe in detail how to modify the well-known algorithm in order to characterize particularly strong light sources from intensity measurements only. With complete information about the optical field of the unknown light source at hand, virtual back propagation can reveal weak points in the light path such as apertures or damaged components.

Temperature Distribution Within an Ignition Kernel Initiated by a Laser-Induced Plasma

The sizes of, and temperature distributions within, ignition kernels initiated by a Q-switched neodymium-doped yttrium aluminum garnet laser-induced plasma in an unconfined lean premixed hydrogen-air upward jet flow are investigated. The experiments involved a range of jet velocities and a range of deposited laser energies at a fixed height above the exit along the axis of a burner. The growth of, and the temperature distributions within, the ignition kernels, as affected by the size and the energy distribution of the laser-induced plasma, are monitored with an infrared camera. The initial ignition kernels’ areas are larger with higher laser pulse energies and remain unchanged up to 20 μs and then increase by factors of up to 3 at 100 μs. The change in the kernel area caused by the jet velocities is less than 1.5%. An increase of the bulk velocity by 190% decreases the ignition kernel temperature by 6%. This reduction in the ignition kernel temperatures is because of an increase in energy losses by a factor of 2 and decreases in heat releases by 2% at 10 μs and by 11% at 100 μs. The present contributions are: measurements of and insights into temperature distributions and kernel development rates during the laser-induced plasma ignition process at different deposited energies and flow velocities.

Spectral splitting in phase mismatched harmonics.

Spectral splitting of high harmonic radiation is observed when a gas target is irradiated with a high-energy laser pulse, having an extreme amount of frequency chirp. The phenomenon, which may be observed only by using a multi-TW laser system, originates from the temporal evolution of the phase-matching conditions. We illustrate how these conditions are mapped to the spectral domain, and present experimental evidence which is validated by our model.

Laser-induced plasma formation in water with up to 400 mJ double-pulse LIBS

Double-pulse LIBS is a promising technique for deep-sea applications. LIBS measurements in shallow water with up to 400 mJ each pulse were done to select laser parameters which promote optimized spectral line emission from plasma even at elevated pressures, where line broadening until loss of most of the spectral information can occur. Optical emission spectroscopy, using a Czerny-Turner spectrometer, has been applied to investigate the dependence of the emitted radiation on laser parameters and hydrostatic pressure. It has been found, that higher laser pulse energies, especially with short pulse delay as required in high water pressure, can also have an adverse effect on the measured spectrum.

Dual-chirped optical parametric amplification of high-energy single-cycle laser pulses

We demonstrate how a scheme called advanced dual-chirped optical parametric amplification (DC-OPA) that employs two kinds of nonlinear crystal (BiB3O6 and MgO-doped lithium niobate) can generate high-energy, single-cycle mid-infrared laser pulses. In experiments, the advanced DC-OPA scheme achieved carrier-to-envelope phase-stable mid-infrared laser pulses with a bandwidth of over one octave (1.4–3.1 µm) and an output pulse energy of 53 mJ. The pulse duration was compressed to 8.58 fs, which corresponds to 1.05 cycles with a central wavelength of 2.44 µm and a peak power of 6 TW. To our knowledge, the obtained values for the pulse energy and peak power are the highest achieved for optical parametric amplification of single-cycle mid-infrared laser pulses. Moreover, owing to the energy scalability of the advanced DC-OPA scheme, the prospects of the multi-terawatt sub-cycle laser pulses are discussed.

Influence of multiple detection events on compositional accuracy of TiN coatings in atom probe tomography

Influence of multiple detection events on compositional accuracy of TiN coatings in atom probe tomography

Recording of Full-Color Snapshot Digital Holographic Portraits Using Neural Network Image Interpolation

For 60 years, high-energy pulsed lasers have enabled the recording of extremely realistic portraits of living people within a few nanoseconds. In the 21st century, this confidential technique, which requires great skill and equipment, has almost disappeared because of the final monochromatic color of the holograms, which does not appeal to the public. In this study, we show that ultra-realistic, full-color, and full-parallax snapshot holographic portraits can be recorded using a limited number of synchronized HD cameras. Experiments were successfully conducted using the digital CHIMERA holographic stereogram printing technique combined with image interpolation using a neural network. This new recording method allows holographic portraits to be developed and disseminated to the public on a larger scale.

Rapid photo-bleaching gamma irradiated Yb-doped optical fibers by high-energy ns pulsed laser

Rapid photo-bleaching gamma irradiated Yb-doped optical fibers by high-energy ns pulsed laser

Generation of high-energy near-infrared femtosecond laser pulses by optical parametric amplification in YCOB crystals

"The energy of near-infrared femtosecond laser pulses generated by optical parametric amplification (OPA) in β-barium borate (BBO) crystals pumped by femtosecond Ti:sapphire lasers is restricted to few-mJ due to the 20 mm limited diam- eter of available crystals. In a type I collinear OPA with an yttrium calcium oxoborate (YCOB) crystal, pumped with femtosecond Ti:sapphire lasers at 800 nm wavelength, the 1300 nm signal wavelength and 2080 nm idler wavelength are located in the normal and anomalous group velocity dispersion range, respectively. Due to the small group velocity mismatch (GVM) between signal and idler pulses, as broad as 27 THz gain bandwidth can be obtained in a 3-mm YCOB crystal at 100 GW/cm2 pump intensity. A high parametric gain is the result of the increased parametric interaction length due to the different signs of GVM between pump-signal and pump-idler pulses. More than 10-mJ energy femtosecond laser pulses at 1300 nm wavelength can be generated by OPA in YCOB crystals with larger than 50 mm clear aperture."

Effects of pulse energy and contact foil thickness on the surface integrity of LY2 aluminum alloy subjected to laser shock wave planishing technology

Reducing the surface roughness is an effective way to improve the fatigue performance of aero-engine blades. In this paper, the milled surface of LY2 aluminum alloy was processed by a laser shock wave planishing (LSWP) technology, and the influence of the laser pulse energy and the contact foil thickness on the surface integrity were studied. The results showed that the thinner the contact foil and the higher the pulse energy were, the higher the removal rate of tool marks (the degree to which the milled topography of LY2 aluminum alloy surface is flattened) was. On the contrary, the thicker the contact foil and the lower the pulse energy were, the lower the removal rate of tool marks was. It will cause ‘center depression’ under LSWP with a thin contact foil and a high laser pulse energy, resulting in an increase of surface roughness, a large difference in residual stress and micro-hardness between the center and the laser spot edge. In the overlapping LSWP experiment, when the contact foil thickness matched the appropriate laser pulse energy, the milled surface was flattened without boundary effect, and in 67% overlapping experiment, a thicker contact foil can be used to achieve the same high-quality surface as in 50% overlapping experiment.

Strong-field vacuum polarisation with high energy lasers

When photons propagate in vacuum they may fluctuate into matter pairs thus allowing the vacuum to be polarised. This linear effect leads to charge screening and renormalisation. When exposed to an intense background field a nonlinear effect can arise when the vacuum is polarised by higher powers of the background. This nonlinearity breaks the superposition principle of classical electrodynamics, allowing for light-by-light scattering of probe and background photons mediated through virtual pairs dressed by the background. Vacuum polarisation is a strong-field effect when all orders of interaction between the virtual pair and the background must be taken into account. In this investigation we show that multiple scattering processes of this type may be observed by utilising high-energy laser pulses with long pulse duration, such as are available at facilities like ELI Beamlines. In combination with appropriate sources of high-energy probe photons, multiple probe-background light-by-light scattering allows for testing the genuine nonlinear regime of strong-field quantum electrodynamics. This provides access to the uncharted non-perturbative regime beyond the weak-field limit.

Unveiling the Elemental Composition and Categorization of Sikkim Hot-Spring Water with Laser-Induced Breakdown Spectroscopy and Advanced Analytical Techniques

The research investigates the elemental composition of hot-spring water in Sikkim, specifically in Yumthang, Tarum, and Reshi, using laser-induced breakdown spectroscopy. This technique involves exciting the sample with a high-energy laser pulse, causing it to emit light that can be analyzed to determine its elemental composition. The results of the study indicate that the hot-spring water in Sikkim is of meteoric origin, meaning it originated from precipitation. To understand the abundance of elements in the hot-spring water samples, the Sulphur/Nitrogen, Chlorine/Nitrogen, and Sulphur/Chlorine ratios were calculated using the ratiometric method. These ratios were then used to classify the samples using univariate and multivariate statistical tools. The box plot was used for the univariate analysis, while the bivariate normal distribution method was used for the multivariate analysis. We have also discussed the limitations of overlapping emission peaks on the classification of the samples. The study found that the abundance of nitrogen in the samples played a significant role in their classification. Principal component analysis was also employed to classify the samples. This technique involves identifying the most significant variables contributing to the variation in the data and using them to classify the samples. Overall, the study provides important insights into the elemental composition of hot-spring water in Sikkim and highlights the usefulness of laser-induced breakdown spectroscopy in analyzing such samples.

Corrosion and passivation behavior of Ti-6Al-4V surfaces treated with high-energy pulsed laser: A comparative study of cast and 3D-printed specimens in a NaCl solution

Corrosion and passivation behavior of Ti-6Al-4V surfaces treated with high-energy pulsed laser: A comparative study of cast and 3D-printed specimens in a NaCl solution

1.7 μm all-fiber figure-9 mode-locked laser based on a fiber Bragg grating

Abstract Fiber lasers operating at 1.7 μm have very important applications in biomedicine, optical imaging, laser welding, optical communication and other fields because of their rich spectral characteristics in the near-infrared band. We designed and experimentally implemented a 1.7 μm all-fiber figure-9 (F9) mode-locked laser, with a fiber Bragg grating (FBG) acting as both the mirror and the spectrum filter. The all-fiber F9 design made the laser work in the mode-locking state more efficiently. We obtained mode-locked pulses with a central wavelength of 1724.76 nm and a repetition rate of 14.39 MHz when the pump power was 1.1 W, and the pulse width was about 54 ps. Limited by the bandwidth of the FBG, the 3 dB bandwidth of the mode-locked spectrum was about 0.18 nm. The output power was 52 mW at a pump power of 2.5 W. The multi-pulse dynamics were studied by adjusting the pump power and the polarization controllers, and pulse trains of up to six pulses in a group were achieved. The 1.7 μm narrow-bandwidth all-fiber F9 mode-locked laser is simple in structure and easy to build, with potential application as a seed source in high-energy ultrashort pulse lasers.

High-power xenon lamp-pumped Er:YAP pulse laser operated in free-running and acousto-optical Q-switching modes

We demonstrate a high-energy and high-power pulse laser on a xenon lamp-pumped Er:YAP crystal. The laser performance and thermal focal lengths under different working frequencies are discussed. The results show that the thermal lens effect is gradually aggravated with the increase of working frequencies, and even working at 100 Hz, a single pulse energy of 234 mJ can be achieved. A maximum average power of 41.5 W is achieved with a working frequency of 20 Hz and slope efficiency of 2.82%. This output power is much higher than other xenon lamp-pumped erbium laser devices. A Q-switched laser is demonstrated by using the TeO2 crystal, the maximum output energies of 11.5 mJ and 3.5 mJ are obtained at 50 and 100 Hz, the corresponding peak powers are 93.4 kW and 17.2 kW, respectively. The laser wavelengths and beam quality factors are also characterized in the free-running and Q-switched modes. A higher pulse energy and peak power laser could be achieved further by improving the damage threshold of TeO2 acousto-optical Q-switching. All the experimental results illustrate that the xenon lamp-pumped Er:YAP laser is a promising candidate for high-power and high-frequency mid-infrared laser devices.

Time evolution of temporal, spatial and spectral distribution of high-energy electron radiation in intense laser pulses

To study the time evolution of high-energy electron radiation in circularly polarized intense laser pulses in detail, a model of the interaction between the high-energy single electron and intense laser pulses is constructed based on the Lagrangian equation and the electron energy equation. Through simulation, this article vividly displays the evolution process of radiation in the spatial, frequency and time domain. By modulating the interaction time between the laser and electron and referring to the spatial distribution image of energy, the value and direction of the maximum radiation energy per unit solid angle are calculated. In addition, in specific directions, this paper discusses the effects of interaction duration on the energy frequency distribution and the power variation pattern. The results prove that the maximum radiation energy per unit solid angle will appear when the interaction time comes to about 450 fs, which is also the boundary moment when the frequency and time spectrum no longer change obviously. Therefore, by modifying the duration of the electron–laser interaction, it is possible to produce the electron radiation with desired characteristics more precisely.

Detection of high-frequency gravitational waves using high-energy pulsed lasers

We propose a new method for detecting high-frequency gravitational waves (GWs) using high-energy pulsed lasers. Through the inverse Gertsenshtein effect, the interaction between a GW and the laser beam results in the creation of an electromagnetic signal. The latter can be detected using single-photon counting techniques. We compute the minimal strain of a detectable GW which only depends on the laser parameters. We find that a resonance occurs in this process when the frequency of the GW is twice the frequency of the laser. With this method, the frequency range 1013–1019 Hz is explored non-continuously for strains for current laser systems and can be extended to with future generation facilities.

400nm ultra-broadband gratings for near-single-cycle 100 Petawatt lasers

Compressing high-energy laser pulses to a single-cycle and realizing the “λ3 laser concept”, where λ is the wavelength of the laser, will break the current limitation of super-scale projects and contribute to the future 100-petawatt and even Exawatt lasers. Here, we have realized ultra-broadband gold gratings, core optics in the chirped pulse amplification, in the 750–1150 nm spectral range with a > 90% −1 order diffraction efficiency for near single-cycle pulse stretching and compression. The grating is also compatible with azimuthal angles from −15° to 15°, making it possible to design a three-dimensional compressor. In developing and manufacturing processes, a crucial grating profile with large base width and sharp ridge is carefully optimized and controlled to dramatically broaden the high diffraction efficiency bandwidth from the current 100–200 nm to over 400 nm. This work has removed a key obstacle to achieving the near single-cycle 100-PW lasers in the future.

Arbitrary Time Shaping of Broadband Low-Coherence Light Based on Optical Parametric Amplification

Laser–plasma interactions (LPIs) hinder the interaction of high-energy laser pulses with targets. The use of broadband low-coherence light has been proposed to reduce the impact of LPIs. In this study, to improve the time–frequency characteristics of broadband low-coherence optical seeds, we proposed an arbitrary time-shaping technique scheme based on optical parametric amplification (OPA) that differs from traditional arbitrary time shaping. The shaping process and output characteristics were analyzed in detail. The theoretical and experimental results show that an arbitrary time-shaping pulse output with a large time-shaping contrast, fast-rising edge, and wide spectral width can be obtained. The time shaping contrast of the shaped pulse can be >300:1, and the spectral width is ~40 nm. The output time waveform is smoother than in traditional schemes, and the noise-like modulation is approximately 4% (approximately equal to the unshaped initial amplified spontaneous emission source). The arbitrary time-shaping scheme based on OPA provides a viable solution for the temporal waveform shaping of broadband low-coherence light.

Micromachining using the high energy flat-top beam of a femtosecond pulse UV laser system: micropillar prefabrication

Ablation with ultrashort laser pulses as a surface micromachining tool was studied using a hybrid die-excimer laser system that has high energy per laser pulse (tens of mJ’s), about 600 fs pulse duration and low repetition rate (2 Hz). The effect of ablation on the material microstructure with this high energy pulsed laser system was studied. Micropillars were fabricated by laser ablation using a spot size of hundreds of micrometers. Two methods were tested for micromachining. Multiple laser pulse ablation on a standing sample resulted in a columnar microscturcure around the micropillars. This unwanted structure was avoided by beam scanning, resulting in a rather homogeneous ditch. By HR-EBSD measurement it was found that the heat affected zone is less than 1 mu textrm{m}, which was confirmed by numerical temperature simulations, too. The dislocation density measured below the specimen surface was unaltered, meaning that no significant crystal degradation occurred. In summary, large-scale micro objects with a diameter in the order of 100~mu textrm{m} without significant change in the crystalline microstructure below the surface, like large-scale micropillars for compression tests, can be fabricated.