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This paper presents overviews of a number of processes and applications associated with high-power, high-intensity lasers, and their interactions. These processes and applications include: free electron lasers, backward Raman amplification, atmospheric propagation of laser pulses, laser driven acceleration, atmospheric lasing, and remote detection...
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... gating in plasmas can generate plasma waves, which trap and accelerate electrons. [54][55][56][57][58][59][60][61][62][63][64][65][66][67][68] In the standard laser wakefield accelerator (LWFA), a short laser pulse, on the order of a plasma wavelength long, excites a trailing plasma wave that can trap and accelerate electrons to high energy (see Fig. 9). Numerous analyses and experiments have been performed to characterize and advance the LWFA concept. However, there are a number of issues that must be resolved before a practical high-energy accelerator can be developed. These include Raman, modulation, and hose instabilities that can disrupt the acceleration process. 68 In addition, ...
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... by spatially tapering the plasma channel. Staging LWFAs can be used to overcome the laser energy loss limitation. Injection, trap- ping, and acceleration in the wakefield continues to be of interest. 77 A simplified, one-dimensional model of the laser wake- field accelerator driven by the ponderomotive force induced by the USPL is shown in Fig. 9. 54 The ponderomotive ...
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Dielectric multilayer coatings exhibiting steep reflectance in an extremely narrow transition zone, highly sensitive to any variations of layer refractive indices and therefore suitable for studying the nonlinear properties are produced and characterized. Increase of reflectance at growing intensity reveals the presence of the optical Kerr effect....
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... It typically ranges from 10 À16 À 10 À15 (negligible, too low turbulence), 10 À15 À 10 À14 (weak turbulence) to 10 À13 À 10 À12 m À2=3 (strong turbulence). For a path length of x ¼ 500 m, Sprangle and Hafizi (2014) show that SI ' 0:1 for weak turbulence and SI ' 1 for strong turbulence. Laserna et al. (2009) report on a laser ablation study very similar to ours but at a long distance of 120 m. ...
The Perseverance rover is carrying out an original acoustic experiment on Mars: the SuperCam microphone records the spherical acoustic waves generated by laser sparks at distances from 2 m to more than 8 m. These N-shaped acoustic waves scatter from the multiple local heterogeneities of the turbulent atmosphere. Therefore, large and random fluctuations of sound travel time and intensity develop as the waves cross the medium. The variances of the travel times and the scintillation index (normalized variance of the sound intensity) are studied within the mathematical formalism of the propagation of spherical acoustic waves through thermal turbulence to infer statistical properties of the Mars atmospheric temperature fluctuation field. The comparison with the theory is made by simplifying assumptions that do not include wind fluctuations and diffraction effects. Two Earth years (about one Martian year) of observations acquired during the maximum convective period (10:00–14:00 Mars local time) show a good agreement between the dataset and the formalism: the travel time variance diverges from the linear Chernov solution exactly where the density of occurrence of the first caustic reaches its maximum. Moreover, on average, waves travel faster than the mean speed of sound due to a fast path effect, which is also observed on Earth. To account for the distribution of turbulent eddies, several power spectra are tested and the best match to observation is obtained with a generalized von Karman spectrum with a shallower slope than the Kolmogorov cascade, ϕ(k)∝(1+k2L2)−4/3. It is associated with an outer scale of turbulence, L, of 11 cm at 2 m above the surface and a standard deviation of 6 K over 9 s for the temperature. These near-surface atmospheric properties are consistent with a weak to moderate wave scattering regime around noon with little saturation. Overall, this study presents an innovative and promising methodology to probe the near-surface atmospheric turbulence on Mars.
... Finally, while the choice of laser intensity has been fixed in the present study for simplicity, the ISC time scales presented here could be reduced in practice by increasing the maximum field strength by up to an order of magnitude before reaching the strong-field regime. 77 As the focus of the present study is to demonstrate the general efficacy of the TD-SOCI approach for tuning excited state dynamics in a simple model compound, these topics are beyond the scope of the current manuscript. ...
Real-time (RT) electronic structure methods provide a natural framework for describing light–matter interactions in arbitrary time-dependent electromagnetic fields (EMF). Optically induced excited state transitions are of particular interest, which require tuned EMF to drive population transfer to and from the specific state(s) of interest. Intersystem crossing, or spin-flip, may be driven through shaped EMF or laser pulses. These transitions can result in long-lived “spin-trapped” excited states, which are especially useful for materials requiring charge separation or protracted excited state lifetimes. Time-dependent configuration interaction (TDCI) is unique among RT methods in that it may be implemented in a basis of eigenstates, allowing for rapid propagation of the time-dependent Schrödinger equation. The recent spin–orbit TDCI (TD-SOCI) enables a real-time description of spin-flip dynamics in an arbitrary EMF and, therefore, provides an ideal framework for rational pulse design. The present study explores the mechanism of multiple spin-flip pathways for a model transition metal complex, FeCO, using shaped pulses designed to drive controlled intersystem crossing and charge transfer. These results show that extremely tunable excited state dynamics can be achieved by considering the dipole transition matrix elements between the states of interest.
... where 2 denotes the strength of turbulence [26]. Parameters for (12) ...
... High power laser systems with exceptional beam quality have many applications in the field of space exploration (Roth and Logan 2015;Guilhot and Ribes-Pleguezuelo 2019), free space laser communication (Chan 2000;Ricklin and Davidson 2002;Bruesselbach et al. 2005b;Cao et al. 2017), light detection and ranging (LiDAR) (Qiu et al. 2019;Poulton et al. 2017Poulton et al. , 2019, directed energy weapons (Jabczyński and Gontar 2021), high energy physics (Sprangle and Hafizi 2014) and material processing (Beyer 2008;Shekel et al. 2020). The primary requirements for these applications are high power and good beam quality, for which combining multiple laser beams is an excellent choice. ...
Coherent combining of light from multiple high power fiber amplifiers is a promising pathway to scaling the output power to hundreds of kiloWatts. In the last decade, substantial progress has been made in terms of scaling number of elements along with improvement in phase control techniques to achieve stable locking, resulting in tens of kiloWatts of output power. In this paper, we review the progress in coherent beam combining of fiber amplifiers in the master oscillator power amplifier configuration. We also discuss the challenges in power scaling as well as the current trends in the corresponding mitigation strategies. Specifically, the use of optimized phase modulation waveforms for mitigation of stimulated Brillouin scattering in high power amplifiers, scaling of the number of beam combining elements through deep-learning based phase control, and the use of micro-lens array for enhancing beam combination efficiency are discussed.
... The representation is based on visible energy photon=1.5eV, high intensity laser field 10 14 Wcm −2 (frequency =10 14 Hz) Sprangle and Hafizi [17], θ = 0.209 radian, η = 1.56radian angle and energy of electron 0 to 600eV. The SI unit for differential crosssection is m 2 . ...
The advancement of laser technology is causing the research field of optics to become more active, and with the help of advancementof technology, more detailed information can be obtained. The primary goal of this work is to calculate differential cross section by using a mathematical model in presence of coulomb potential and elliptically polarized beam with single photon absorption. The developed model shows the differential cross section increases with wavelength and decreases with electron energy with elliptically polarized beam. The differential cross section become maximum at 1.56 radian polarized angle and minimum at -1.56 radian polarized angle. The observation is based on 1.5eV laser photon energy, laser field intensity 1014Wcm−2 , polarized angle 1.56 radian angle, and electron energy 0 to 600eV. Using the born first approximation and the Volkov wave function, the developed equation is obtained. The numerically obtained differential crosssection in this work is approximately 10 −19𝑚2 to 10 −20𝑚2 , which is less than the differential cross section obtained by Flegel et al. (2013), which is approximately 10 −17𝑚2 .
... 5, gives a governing relationship between the F and Ep, M 2 , λ, f and db as The size as well as the intensity distribution profile of the projected beam within the irradiated area affect the material response to the applied laser energy [116]. Also, the laser beam propagation characteristics are known to vary during processing in high power laser delivery systems [117]. A small change in the focal length has a measurable effect on the spot size and the intensity distribution of the projected beam, which in turn influences the stability of the machining process, the local material response and overall the MRR [116]. ...
Ultra-fast femtosecond (fs) lasers provide a unique technological opportunity to precisely and efficiently micromachine materials with minimal thermal damage owing to the reduced heat transfer into the bulk of the work material offered by short pulse duration, high laser intensity and focused optical energy delivered on a timescale shorter than the rate of thermal diffusion into the surrounding area of a beam foci. There is an increasing demand to further develop the fs machining technology to improve the machining quality, minimize the total machining time and increase the flexibility of machining complex patterns on diamond. This article offers an overview of recent research findings on the application of fs laser technology to micromachine diamond. The laser technology to precisely micromachine diamond is discussed and detailed, with a focus on the use of fs laser irradiation systems and their characteristics, laser interaction with various types of diamonds, processing and the subsequent post-processing of the irradiated samples and, appropriate sample characterisation methods. Finally, the current and emerging application areas are discussed, and the challenges and the future research prospects in the fs laser micromachining field are also identified.
... The study of the evolution of the laser pulse as it propagates in the tenuous plasma has drawn considerable research interest around the globe both theoretically and experimentally. [2][3][4][5] The propagation of the laser pulse in the underdense plasma (n e < n c ) has been studied in the past. 4,6,7 The propagation of the laser in plasma also leads to a nonlinear phenomenon resulting in soliton formation. ...
... We have numerically solved Eqs. (1)- (5) in the same sequence to study the evolution of the laser pulse entering the simulation box from the left side. The simulation box of length 100 k is considered, with a constant unperturbed plasma density n 0 throughout the simulation domain; the linearly polarized Gaussian laser pulse of wavelength 800 nm has a full width half maximum (FWHM) duration of 3 cycles (s fwhm ¼ 3 Â 2p). ...
The propagation of laser pulses in the underdense plasma is a very crucial aspect of the laser-plasma interaction process. In this work, we explored the two regimes of laser propagation in the plasma, one with a0 < 1 and the other with a0≳10. For the a0 < 1 case, we used a cold relativistic fluid model, wherein apart from immobile ions no further approximations are made. The effects of laser pulse amplitude, pulse duration, and plasma density are studied using the fluid model and compared with the expected scaling laws and also with the particle-in-cell (PIC) simulations. The agreement between the fluid model and the PIC simulations are found to be excellent. Furthermore, for the a0≳10 case, we used the PIC simulations alone. The delicate interplay between the conversion from the electromagnetic field energy to the longitudinal electrostatic fields results in dispersion, and so the redshift of the pump laser pulse. The dispersed pulse is then allowed to be incident on the subwavelength two-layer composite target. The underdense plasma before the target regulates the dispersion of the pulse. We observed an optimum pretarget plasma density which results in the acceleration of the ions from the secondary layer to ∼170 MeV by a ∼8 fs linearly polarized Gaussian laser pulse with ∼8.5 × 10²⁰ W/cm².
... High average power CW (greater than 10 kW) and highintensity (up to 1 TW∕cm 2 ) short pulse lasers (with pulse lengths ranging from hundreds of femtoseconds to greater than a nanosecond) play important roles in a number of areas such as active and passive remote sensing [1][2][3][4][5][6], power beaming [7], communications, directed energy [7,8], electronic counter measures, and induced electric discharges (artificial lighting) [9,10]. In addition, high-intensity short pulse lasers are employed for fundamental high-intensity laser matter interaction and nonlinear optics studies. ...
The effect of laser noise on the atmospheric propagation of high-power CW lasers and high-intensity short pulse lasers in dispersive and nonlinear media is studied. We consider the coupling of laser intensity noise and phase noise to the spatial and temporal evolution of laser radiation. High-power CW laser systems have relatively large fractional levels of intensity noise and frequency noise. We show that laser noise can have important effects on the propagation of high-power as well as high-intensity lasers in a dispersive and nonlinear medium such as air. A paraxial wave equation, containing dispersion and nonlinear effects, is expanded in terms of fluctuations in the intensity and phase. Longitudinal and transverse intensity noise and frequency noise are considered. The laser propagation model includes group velocity dispersion, Kerr, delayed Raman response, and optical self-steepening effects. A set of coupled linearized equations are derived for the evolution of the laser intensity and frequency fluctuations. In certain limits, these equations can be solved analytically. For example, we find that, in a dispersive medium, frequency noise can couple to and induce intensity noise (fluctuations) and vice versa. At high intensities, the Kerr effect can reduce this intensity noise. In addition, significant spectral modification can occur if the initial intensity noise level is sufficiently high. Finally, our model is used to study the transverse and longitudinal modulational instabilities. We present atmospheric propagation examples of the spatial and temporal evolution of intensity and frequency fluctuations due to noise for laser wavelengths of 0.85 μm, 1 μm, and 10.6 μm.
... where c is the speed of light, ω p = (4πn p e 2 /m) 1/2 is the electron plasma frequency, -e and m are the electron charge and mass, respectively, ω 0 is the laser frequency and η is the refractive index of the plasma. Since an electromagnetic (EM) wave propagating in a uniform plasma, has a group velocity less than the speed of light, the ponderomotive potential associated with a laser pulse can trap the plasma electrons (Liu et al., 2007;Sprangle & Hafizi, 2014). In fact, a laser pulse propagating through a plasma medium travels at lower velocities compared with when it propagates in vacuum and it can act as a slow wave. ...
A linearly polarized laser pulse has been employed as a wiggler in a free-electron laser (FEL) in the presence of a plasma background for generating short wavelength radiation down to the extreme ultraviolet ray and X-ray spectral regions. Introducing plasma background in the FEL interaction region would lessen the beam energy requirement and also enhance both the beam current and the electron-bunching process. This configuration affords the possibility of scaling the device to more compact FELs and would have a higher tunability by changing the plasma density and the temperature of the electron beam. Electron trajectories have been analyzed using single-particle dynamics. The effect of plasma density on electron orbits has been investigated. A polynomial dispersion relation considering longitudinal thermal motion has been derived, by employing perturbation analysis. Numerical studies indicate that by increasing plasma density, the growth rate for groups I and II decreases, while the growth rate for group III increases. In addition, the effect of beam temperature and cyclotron frequency on the growth rate has been discussed. It has been found that by increasing the thermal velocity of the electron beam, the growth rate for groups I and III trivially decreases, while it increases for group II orbits. Besides, an increase in cyclotron frequency cause growth enhancement for group I orbits, while it present a growth decrement for group II and III orbits.
... The ionization of the target and the formation of the plasma ahead of the main target has very dramatic consequences which in a sense can completely alter the dynamics of the interaction. The study of the evolution of the laser pulse as it propagates in the tenuous plasma has drawn considerable research interest around the globe both theoretically and experimentally [15][16][17][18]. The propagation of the laser pulse in the under-dense plasma (n e < n c ) has been studied in the past [17,19]. ...
The propagation of the laser pulses in the underdense plasma is a very crucial aspect of laser-plasma interaction process. In this work, we explored the two regimes of laser propagation in plasma, one with $a_0 < 1$ and other with $a_0 \gtrsim 10$. For $a_0<1$ case, we used a cold relativistic fluid model, wherein apart from immobile ions no further approximations are made. The effect of the laser pulse amplitude, pulse duration, and plasma density is studied using the fluid model and compared with the expected scaling laws and also with the PIC simulations. The agreement between the fluid model and the PIC simulations are found to be excellent. Furthermore, for $a_0 \gtrsim 10$ case, we used the PIC simulations alone. The delicate interplay between the conversion from the electromagnetic field energy to the longitudinal electrostatic fields results in the dispersion and so the red-shift of the pump laser pulse. We also studied the interaction of the dispersed pulse (after the propagation in underdense plasma) with the sub-wavelength two-layer composite target. The ions from the thin, low-density second layer are found to be efficiently accelerated to $\sim 70$ MeV, which is not found to be the case without dispersion.
