Probing ultrafast laser plasma processes inside solids with resonant small-angle X-ray scattering

Decreasing ultrafast X-ray pulse durations with saturable absorption and resonant transitions

Saturable absorption is a nonlinear effect where a material's ability to absorb light is frustrated due to a high influx of photons and the creation of electron vacancies. Experimentally induced saturable absorption in copper revealed a reduction in the temporal duration of transmitted X-ray laser pulses, but a complete understanding of this process is still missing. In this computational work, we employ non-local thermodynamic equilibrium plasma simulations to study the interaction of femtosecond X-rays and copper. Following the onset of frustrated absorption, we find that a $K\text{--}M$ res…

Probing Ultrafast Magnetic-Field Generation by Current Filamentation Instability in Femtosecond Relativistic Laser-Matter Interactions

We present experimental measurements of the femtosecond time-scale generation of strong magnetic-field fluctuations during the interaction of ultrashort, moderately relativistic laser pulses with solid targets. These fields were probed using low-emittance, highly relativistic electron bunches from a laser wakefield accelerator, and a line-integrated $B$-field of $2.70 \pm 0.39\,\rm kT\,μm$ was measured. Three-dimensional, fully relativistic particle-in-cell simulations indicate that such fluctuations originate from a Weibel-type current filamentation instability developing at submicron scales …

利用时间分辨共振X射线吸收和发射探测等离子体超快加热和电离动力学

Probing ultrafast heating and ionization dynamics in solid density plasmas with time-resolved resonant X-ray absorption and emission

本文通过时间分辨共振X射线发射和吸收成像技术，研究高强激光与细丝靶相互作用中的超快加热和电离过程，结合原子碰撞辐射模型等模拟揭示等离子体参数的极端敏感性。

Long range propagation of ultrafast, ionizing laser pulses in a resonant nonlinear medium

We study the propagation of 0.05-1 TW power, ultrafast laser pulses in a 10 meter long rubidium vapor cell. The central wavelength of the laser is resonant with the $D_2$ line of rubidium and the peak intensity in the $10^{12}-10^{14} ~W/cm^2$ range, enough to create a plasma channel with single electron ionization. We observe the absorption of the laser pulse for low energy, a regime of transverse confinement of the laser beam by the strong resonant nonlinearity for higher energies and the transverse broadening of the output beam when the nonlinearity is saturated due to full medium ionizatio…

超快激光诱导固体至过稠密等离子体转变的光学探测

Optical Probing of Ultrafast Laser-Induced Solid-to-Overdense-Plasma Transitions

该研究利用单发近红外探针透射测量并结合固态与动力学等离子体模型，可视化纳米类金刚石碳膜在低强度激光上升沿向过稠密等离子体转变的亚皮秒过程。

Air hydrodynamics of the ultrafast laser-triggered spark gap

We present space and time resolved measurements of the air hydrodynamics induced by ultrafast laser pulse excitation of the air gap between two electrodes at high potential difference. We explore both plasma-based and plasma-free gap excitation. The former uses the plasma left in the wake of femtosecond filamentation, while the latter exploits air heating by multiple-pulse resonant excitation of quantum molecular wavepackets. We find that the cumulative electrode-driven air density depression channel initiated by the laser plays the dominant role in the gap evolution leading to breakdown.