High harmonic generation

Application note HHG

The process of high harmonic generation (HHG) enables the development of table-top sources of coherent extreme ultraviolet (XUV) light. However, they mostly rely on bulk laser technology that limits the attainable repetition rate to the low kilohertz regime. By contrast, many of the emerging applications of such light sources e.g. photoelectron spectroscopy and microscopy, coherent diffractive imaging (CDI) [1] or extreme ultraviolet coherence tomography (XCT) [2] require a higher repetition rate. Impressive results regarding power scaling of the harmonics have been achieved in university labs in collaboration with AFS [3].

AFS offers not only suitable high power fiber lasers to drive such generation processes, but also entire XUV beamlines of significantly reduced complexity generating intensive XUV flux of up to 1014 photons/s at 21 eV, 5×1010 photons/s at 90 eV and 1010 photons/s at 150 eV at a flexible repetition rate with turnkey reliability. Even higher photon energies up to the soft X-ray regime (e.g. 330 eV [4]) are feasible using Tm-based driving lasers.

We employ a gas-filled photonic cystal fiber or a multi-pass cell for efficient nonlinear pulse compression in order to use these ultrashort pulses for high harmonic generation in a gas jet [5,6].