High-order harmonic generation (HHG)

High-order harmonic generation (HHG): production of extreme ultraviolet (XUV) emission by interaction of an intense infrared laser field with typically an atomic or molecular target. The underlying physics is well described by the semiclassical three-step model, in which an electron initially in the ground state is freed into the continuum by tunnel ionization, accelerated and ultimately driven back to the core by the oscillating linearly polarized laser ﬁeld where it may recombine and emit a high energy harmonic photon.

Attosecond pulse generation: HHG can be used to generate a single attosecond pulse or an attosecond pulse train (APT). Single attosecond pulses are repeated at the pulse repetition rate of the intense infrared laser field that is used for HHG.

HHG characterization in collaboration with Prof. Anne L’Huillier:
Measurement and control of the frequency chirp rate of high-order harmonic pulses: DownloadRef. [205] (PDF, 400 KB)
Characterization of high-order harmonic radiation on femtosecond and attosecond time scales: DownloadRef. [196] (PDF, 1.5 MB)
Time-frequency characterization of femtosecond XUV pulses: DownloadRef. [165] (PDF, 136 KB)

Large enhancement of HHG is discussed in the following References:
Initial proposal for strong field quantum path control using attosecond pulse trains (single atom response): DownloadRef. [190] (PDF, 177 KB)
Theoretical prediction for a large enhancement of macroscopic yield in APT-assisted harmonic generation (taking into account phase matching): DownloadRef. [231] (PDF, 507 KB)
Initial experiments: DownloadRef. [242] (PDF, 1.3 MB)