Intra-cavity extreme ultraviolet light source based on a mode locked Ti:Sapphire oscillator with 9.4 MHz repetition rate

Sources based on high harmonic generation (HHG) deliver line and/or continuum radiation up to few keV with excellent spatial characteristic and repetition rate up to few kHz. These sources have been successfully applied for x-ray absorption spectroscopy with sub-20 fs temporal resolution. However, for time-resolved photoelectron spectroscopy there is a need for pulsed EUV sources with MHz repetition rate. The intensity achieved at the output of an ultrafast Ti:sapphire lasers is too low for high harmonic generation. So for realizing MHz repetition rate EUV sources the peak power of femtosecond Ti:sapphire based oscillators have been enhanced by either an external enhancement cavity or plasmonic field enhancement with nanostructured samples. In this contribution we report on a new approach, namely the intracavity high harmonic generation in a Ti:sapphire oscillator with repetition rate of 9.4 MHz. This rather simple intra-cavity EUV source will provide new opportunities in spectroscopy.