Yasuo Nabekawa | Searcharxiv

arXiv2026

Submicrometer focusing of isolated attosecond XUV pulses approaching 10$^{16}$ W/cm$^2$

We demonstrate submicrometer focusing of isolated attosecond pulses (IAPs) in the extreme ultraviolet (XUV) region using a custom ellipsoidal mirror. The obtained focal spot sizes were verified using knife-edge measurements with a sharp silicon edge, confirming reproducible dimensions down to 0.46 $μ$m $\times$ 0.36 $μ$m (FWHM), approaching the diffraction limit. Focusing a 1.1-GW tabletop IAP source yields a peak intensity of 3 $\times$ 10$^{15}$ W/cm$^2$, and a realistic pathway toward 10$^{16}$ W/cm$^2$ is obtained by optimizing the beamline throughput. These results establish a practical route toward attosecond nonlinear optics in both gas and solid phases, driven by intense XUV fields.

physics.optics↗

arXiv2024

Perturbed three-channel waveform synthesizer for efficient isolated attosecond pulse generation and characterization

The generation of gigawatt-class isolated attosecond pulses (IAPs) is vital for attosecond pump-probe experiments. In such experiments, the temporal duration of IAPs must be determined quickly and accurately. In this study, we developed a perturbed three-channel waveform synthesizer for efficient IAPs generation and characterization at low repetition rates ( 10 Hz). Intense IAPs centered at photon energies of 60 eV (227 as duration) in Ar and 107 eV (128 as duration) in Ne were generated by the driving field from a three-channel waveform synthesizer and characterized using all-optical frequencyresolved optical gating (AO-FROG), which accelerated the measurement time to several minutes, providing fast feedback for the tunability of the IAP source. The peak power of the IAPs is higher than that reported in the literature.

physics.optics↗