Maximizing energy deposition by shaping few-cycle laser pulses

We experimentally investigate the impact of pulse shape on the dynamics of laser-generated plasma in rare gases. Fast-rising triangular pulses with a slower decay lead to early ionization of the gas and depose energy more efficiently than their temporally reversed counterparts. As a result, in both argon and krypton, the induced shockwave as well as the plasma luminescence are stronger. This is due to an earlier availability of free electrons to undergo inverse Bremsstrahlung on the pulse trailing edge. Our results illustrate the ability of adequately tailored pulse shapes to optimize the energy deposition in gas plasmas

Laser vaporization of cirrus-like ice particles with secondary ice multiplication

We investigate the interaction of ultrashort laser filaments with individual 90-μm ice particles, representative of cirrus particles. The ice particles fragment under laser illumination. By monitoring the evolution of the corresponding ice/vapor system at up to 140,000 frames per second over 30 ms, we conclude that a shockwave vaporization supersaturates the neighboring region relative to ice, allowing the nucleation and growth of new ice particles, supported by laser-induced plasma photochemistry. This process constitutes the first direct observation of filament-induced secondary ice multiplication, a process that strongly modifies the particle size distribution and, thus, the albedo of typical cirrus clouds

Optimal laser-pulse energy partitioning for air ionization

We investigate the pulse partitioning of a 6.3-mJ, 450-fs pulse at 1030 nm to produce plasma channels. At such moderate energies, splitting the energy into several subpulses reduces the ionization efficiency and thus does not extend the plasma lifetime. We numerically show that when sufficient energy to produce multifilamentation is available, splitting the pulse temporally in a pulse train increases the gas temperature compared to a filament bundle of the same energy. This could improve the mean free path of the free electrons, therefore enhancing the efficiency of discharge triggering

Survival and osmoregulation of the purple marsh crab (Sesarma reticulatum) at varying salinity and pH

Overfishing of top predators along the western Atlantic coastline has led to a trophic cascade in salt marshes, with increases in herbivorous purple marsh crab (Sesarma reticulatum; Say, 1817) abundances in North American estuaries leading to overgrazing of cordgrass (Spartina alterniflora, Loisel.) and shoreline erosion. To evaluate potential physiological limits on the range of S. reticulatum within an estuary, we evaluated survival and physiological tolerance of S. reticulatum from the Ashepoo-Combhee-Edisto (ACE) River Basin in South Carolina, USA, to combinations of salinity (5 and 30 â °) and pH (pH 6.6, 7.6, and 8.6) challenges, representative of estuarine extremes. Survival, haemolymph ion concentrations, and gill NaThe accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Laser vaporization of cirrus-like ice particles with secondary ice multiplication

We investigate the interaction of ultrashort laser filaments with individual 90 µm ice particles, representative of cirrus particles. The ice particles fragment under laser illumination. By monitoring the evolution of the corresponding ice/vapour system at up to 140,000 frames per second over 30 ms, we conclude that a shockwave vaporization supersaturates the neighbouring region relative to ice, allowing the nucleation and growth of new ice particles, supported by laser-induced plasma photochemistry. This process constitutes the first direct observation of filament-induced secondary ice multiplication (FISIM), a process that strongly modifies the particle size distribution, hence the albedo, of typical cirrus clouds

Laser Induced Aerosol Formation Mediated by Resonant Excitation of Volatile Organic Compounds

Since its first demonstration, Laser Induced Aerosol Formation (LIAF) was studied in various environmental conditions and laser parameters. LIAF driven by UV and near-IR lasers mainly relies on the nitrogen photo-oxidative chemistry, leading to the production of hygroscopic HNO3, which stabilizes the growth of aerosol nanoparticles. Mid-IR lasers were expected to be drastically less effective for LIAF, due to their much lower multiphoton photodissociation and ionization rates. Here we report on the observation of surprisingly high yields of nano-metric and sub-µm aerosol formation driven by mid-IR laser pulses, which cannot be explained by the HNO3-pathway. We hereby evidence a new mechanism of aerosol stabilization and growth, based on the resonant excitation of volatile organic compounds (VOCs) by mid-IR pulses whose spectrum is broadened during filamentation

Cooperative effect of ultraviolet and near-infrared beams in laser-induced condensation

We demonstrate the cooperative effect of near infrared (NIR) and ultraviolet (UV) beams on laser-induced condensation. Launching a UV laser after a NIR pulse yields up to a 5-fold increase in the production of nanoparticles (25–300 nm) as compared to a single NIR beam. This cooperative effect exceeds the sum of those from the individual beams and occurs for delays up to 1 μs. We attribute it to the UV photolysis of ozone created by the NIR pulses. The resulting OH radicals oxidize NO2 and volatile organic compounds, producing condensable species

White-light femtosecond Lidar at 100 TW power level

We characterized the white-light supercontinuum emission by a sub-petawatt laser system in the atmosphere via light detection and ranging measurements. As much as 1 J of supercontinuum is generated in the atmosphere, corresponding to a conversion efficiency of 30 %. This generation occurs at altitudes below 100 m. The high initial beam intensity results in the saturation of the number of self-guided filaments. Therefore, the “photon bath” surrounding the filaments strongly contributes to the white-light generation. These finding is well reproduced by numerical simulations based on the experimental parameters