Optimization of harmonic generation from boron plasma

Abstract

The plateau pattern of the harmonic distribution up to the 65th order (λ=12.24nm) and the 5×10−7 conversion efficiency were achieved after the propagation of femtosecond pulses through the laser-produced boron plasma. The optimization of high-order harmonics generation was carried out at the focusing conditions when the confocal parameter of fundamental radiation was close to the plasma sizes. A study of cutoff energy showed its dependence on the second ionization potential of nonlinear medium. The spatial distribution of the radiation propagating through the boron plume showed the appearance of ringlike pattern at the intensities exceeding a saturated intensity of singly charged ions.

Harmonic generation in laser-produced plasmas containing atoms, ions and clusters: a review

“…A new history of plasma HHG studies based on this approach started in 2005. It immediately followed with the observation of extended harmonics and considerably higher conversion efficiencies [19][20][21][22][23], which became comparable with those reported in gas HHG studies. During the following few years, enormous improvements in the characteristics of this process were reported.…”

“…This technique provides an efficient method for optimising the plasma conditions for harmonic generation. Previous studies of HHG from plasma plumes have analysed the UV emission spectrum from the plasma, which aimed to prove that over-excited and/or over-ionised plasma could dramatically decrease the harmonic intensity [21,22,31]. However, as was mentioned above, these spectral measurements were performed using the time-integrated methods that did not allow the identification of the plasma state before the interaction with the delayed femtosecond pulse.…”

Harmonic generation from partially ionized plasma [Invited]

“…The advantages of plasma HHG could largely be realized with the use of low-excited and weakly ionized plasma, because the limiting processes governing the dynamics of harmonic generation would play a minor role, as shown for the first time in the case of boron plasma [25]. This assumption has been confirmed during several other studies of HHG in plasma media [26][27][28]. The highest-order harmonics (above the hundredth order) have been demonstrated during ablation of manganese [29] and currently can be routinely achieved using moderate level (a few tens of femtoseconds and a few milijoules) laser pulses.…”

Time-resolved spectroscopy of plasma plumes: A versatile approach for optimization of high-order harmonic generation in laser plasma

“…Recent studies of HHG from plasma plumes have analyzed the ultraviolet emission spectrum from the plasma, which aimed to prove that overexcited and=or over-ionized plasma can dramatically decrease the harmonic intensity. 15,19 However, these spectral measurements were performed using time-integrated methods that did not allow the investigation of the true plasma state before the interaction with the delayed femtosecond pulse.…”