Speaker
Description
Bright high-harmonic radiation from relativistically oscillating laser plasmas provides a direct route to generating extreme electromagnetic fields. Theory predicts that, under optimal conditions, the plasma can compress laser energy spatiotemporally into a Coherent Harmonic Focus (CHF), producing intensity boosts many orders of magnitude above the driving laser pulse. Diffraction-limited focusing and attosecond phase-locking have been demonstrated experimentally, but efficient coupling of relativistic laser energy into the harmonic emission cone has not previously been achieved.
Here we present that relativistic laser plasma interactions can be tuned to reach the high conversion efficiencies predicted by simulations. By enhancing the temporal profile of the driving pulse, we measure energies of 9 mJ between the 12th and 47th harmonics (18–73 eV). The measured efficiency scaling with harmonic order matches theoretical expectations, indicating near-optimal generation conditions. Achieving optimal efficiency together with full spatiotemporal compression remains challenging, these results open a path toward optical field strengths approaching the Schwinger limit $\mathbf{>10^{16}}$ V/m or $\mathbf{>10^{29}}$ W.cm$^{-2}$), enabling all-optical studies of the quantum vacuum and new frontiers in intense attosecond science.
| Working group | WG6 |
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