Ablation of boron carbide for high-order harmonic generation of ultrafast pulses in laser-produced plasma

• We have demonstrated the harmonic generation up to the 27th order (λ=29.9 nm) of 806 nm driving pulses in the boron carbide laser-produced plasma.
• We have analyzed the advantages and disadvantages of this target compared with the ingredients comprising B4C.
• We have compared different schemes of the commensurate and incommensurate two-color pumps of B4C plasma.
• The spatial characterization of harmonics have shown their modification depending on the conditions of high-order harmonic generation.

We demonstrate the generation of harmonics up to the 27th order (λ=29.9 nm) of 806 nm radiation in the boron carbide plasma. We analyze the advantages and disadvantages of this target compared with the ingredients comprising B4C (solid boron and graphite) by studying the plasma emission and harmonic spectra from three species. We compare different schemes of the two-color pump of B4C plasma, particularly using the second harmonics of 806 nm laser and optical parametric amplifier (1310 nm) as the assistant fields, as well as demonstrate the sum and difference frequency generation using the mixture of the wavelengths of two laser sources. These studies showed the advantages of the two-color pump of B4C plasma leading to the stable harmonic generation and the growth of harmonic conversion efficiency. We also show that the coincidence of harmonic and plasma emission wavelengths in most cases does not cause the enhancement or decrease of the conversion efficiency of this harmonic. Our spatial characterization of harmonics shows their on-axis modification depending on the conditions of frequency conversion.