Ultrafast Space-time and Spectrum-time Resolved Diagnostics of Multicharged Femtosecond Laser Microplasma

Abstract

Articles you may be interested inWall current probe: A non-invasive in situ plasma diagnostic for space and time resolved current density distribution measurement Rev. Sci. Instrum. 84, 083502 (2013); Abstract. We present the review of the recent experimental studies of fundamental mechanisms of femtosecond laser plasma formation and evolution performed in A.M. Prokhorov General Physics Institute of Russian Academy of Sciences. The main object we dealt with was the microsized plasma produced in gases with high intensity (up to 5xlO" W/cm^), tightly focused (to a few microns in diameter) IR and UV femtosecond laser pulses. The main attention in the experiments was paid to the initial stage of microplasma formation and evolution characterized by strong laser-plasma coupling resulting in efficient ionization and heating of the medium, distortion of laser beam, and nonlinear spectral conversion of laser radiation to the continuum and laser harmonics. Using a precise pump-probe micro-interferometric technique the dynamics of plasma was studied with femtosecond time-resolution in a wide density range -from a minimal detectable electron concentration (lO" cm"') to the almost total (down to nuclei) ionization of ions occurred under femtosecond excitation. The obtained time-dependences of plasma density were analyzed. It was observed, for the first time, that a characteristic time of femtosecond laser plasma formation in gases considerably (in times) exceeds the duration of the pump laser pulse. This postionization process is attributed to impact ionization of plasma by hot electrons. We compare the results of the experiments with what the developed theory predicts. Using an ultrafast streak-camera-based spectroscopy technique the temporal evolution of microplasma emission and the dynamics of spectral lines formation in UV-visible range were studied with picosecond time-resolution.

Picosecond Ionization Dynamics in Femtosecond Filaments at High Pressures

“…The postpulse dynamics resulting from collisional ionization is interesting not only to provide a fundamental understanding but also to shed light on the physical processes that occur during the pulse. Measurements of postpulse electron dynamics have been made using interferometry in a hot plasma [12] or indirectly via four-wave mixing [13] or via Rabi oscillations [14]. The laser intensity used in these experiments was sufficiently high ( 5 × 10 14 W/cm 2 ) so that the ponderomotive energy was * a.gaeta@columbia.edu comparable to the ionization potential, which gives rise to an increase in the plasma density by tens of percent in agreement with simulations [15].…”

The interaction of intense femtosecond laser pulses with argon microdroplets studied near the soft x-ray emission threshold

“…The interaction of intense near-infrared (NIR) laser light with small particles has been of particular interest in the last decades, since it allows us to study matter of finite size under extreme conditions [1][2][3][4][5][6][7]. Due to the strong absorption capabilities, nanoparticles are effectively transformed into nanoplasmas [8], which results in the emission of highly charged and energetic ions [9][10][11] and fast electrons [12,13].…”

“…Figure 4. Experimental dependence of the Ar +7 3p-4d EUV signal on pulse duration for a given pulse energy of 1.4 mJ (see figure3). The data are normalized to the pulse duration of 100 fs.…”

A Novel Acoustic Diagnostic Method on Femtosecond Laser Plasma Shock Wave

“…Chen, J.K. proposed the correction dual temperature model based on this [2]. For one thing, in the aspect of the laser plasma analysis technology, S. V. Garnov observed plasma formation, progress and ionization process in the early stage using ultra-fast spectroscopy technique [3]. Wang Guangxu measured the transition radiation integral imaging spot pattern and the transition radiation spectrum using optical CCD camera and optical multi-channel analyzer (OMA)，the transition radiation integral imaging spot pattern and the transition radiation spectrum were produced by the interaction between super oblique incident femtosecond laser and plasma, some experimental results have reference value [4].…”