Sprecher
Beschreibung
Relativistic oscillating plasma mirrors provide a promising platform for generating bright high-harmonic radiation and, ultimately, extreme electromagnetic fields. Theory predicts that, under optimized conditions, these systems can strongly compress laser energy in space and time, forming a Coherent Harmonic Focus (CHF) with intensities orders of magnitude beyond those of the driving pulse. While previous experiments have demonstrated diffraction-limited harmonic emission and attosecond phase locking, efficiently coupling highly relativistic laser energy into the emitted harmonic cone has remained an outstanding challenge.
Here we present the first conclusive experimental evidence that this coupling can be optimized to reach the conversion efficiencies predicted by simulations. By precisely shaping the driving laser’s temporal profile on femtosecond timescales, we obtain >9 mJ of harmonic energy between the 12th and 47th orders (18–73 eV). The measured harmonic yields follow the theoretically expected efficiency scaling with harmonic order, indicating that the underlying plasma dynamics have been tuned to optimal conditions.
These results complete the final missing step toward realizing CHF-level intensity boosts in the laboratory. Although simultaneous spatial and temporal compression at peak efficiency remains a challenge, this work establishes a clear pathway to generating optical field strengths approaching the quantum-electrodynamic critical field, opening new opportunities for all-optical studies of vacuum physics and extreme attosecond science.
