Eiji J. Takahashi

Towards intense single-digit attosecond pulses with a 100-mJ-class mid-infrared sub-cycle laser

The duration of isolated attosecond pulses created via high-order harmonic generation is determined by the number of optical cycles in the driving laser. Achieving shorter attosecond soft x-ray pulses requires minimizing the number of cycles while maintaining a high pulse energy....

Complex-gate all-optical frequency-resolved optical gating for ultrabroadband isolated attosecond pulse characterization

We experimentally demonstrate all-optical frequency-resolved optical gating (AO-FROG) for the characterization of ultrabroadband isolated attosecond pulses (IAPs) generated by a mid-infrared sub-cycle laser field. By extending the AO-FROG framework beyond the conventional phase-o...

Submicrometer focusing of isolated attosecond XUV pulses approaching 1016 W/cm2

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 dimen...