Extreme-ultraviolet high-order harmonic generation from few-cycle annular beams

Area of Science:

• Atomic, Molecular, and Optical Physics
• Ultrafast Science
• Laser Physics

Background:

• High-order harmonic generation (HHG) is crucial for producing extreme-ultraviolet (XUV) pulses.
• Traditional methods face challenges with high-power infrared (IR) lasers damaging optics.
• Attosecond pump-probe experiments require stable, well-defined XUV and IR pulses.

Purpose of the Study:

• To demonstrate a novel method for high-order harmonic generation using an annular IR laser beam.
• To improve the stability and efficiency of XUV pulse generation for pump-probe experiments.
• To reduce the destructive effects of residual IR radiation on experimental apparatus.

Main Methods:

• Utilized an annular infrared laser beam for high-order harmonic generation.
• Achieved harmonic generation in the central, IR-free region of the beam.
• Employed thin metallic foils for residual IR removal and XUV pulse shaping.

Main Results:

• Generated high-order harmonics with a cut-off energy of 90 eV.
• Successfully separated the generated XUV pulses from the residual IR beam.
• Demonstrated reduced IR power load on metallic foils.

Conclusions:

• The annular IR laser approach offers enhanced stability for attosecond beamlines.
• This technique is suitable for high-average-power few-cycle laser systems.
• Spatial separation of IR and XUV simplifies attosecond time-resolved measurements.