Complex Attosecond Waveform Synthesis at FEL FERMI

Free-electron lasers (FELs) can produce radiation in the short wavelength range extending from extreme ultraviolet (XUV) to X-rays with a few tens of femtoseconds pulse duration. These facilities have enabled significant breakthroughs field atomic, molecular, and optical physics, implementing different schemes based on two-color photoionization mechanisms. In this article, we present generation attosecond trains (APTs) at seeded FEL FERMI using beating multiple phase-locked harmonics. We demonstrate complex waveform shaping generated APTs, exploiting ability manipulate independently amplitudes phases The described generalized synthesis technique an arbitrary number harmonics will allow sub-100 as pulses programmable electric fields.