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Electron trajectory selection for high harmonic generation inside a short hollow fiber
Optics Express
|October 10, 2013
Summary
Investigating high harmonic generation, this study found that a 300-μm hollow fiber produced better beam quality than a gas jet. However, a 200-μm hollow fiber resulted in a more divergent beam due to trajectory effects.
Area of Science:
- * Nonlinear Optics and Laser Physics
- * High Harmonic Generation (HHG)
Background:
- * High harmonic generation (HHG) is a crucial process for producing extreme ultraviolet (XUV) and soft X-ray radiation.
- * The beam quality of HHG sources is critical for applications in spectroscopy, microscopy, and attosecond science.
- * Gas jets and hollow fibers are common media for HHG, each with distinct characteristics influencing beam quality.
Purpose of the Study:
- * To investigate and compare the beam divergences and quality (M²) of 19th harmonic beams generated via HHG.
- * To evaluate the performance of Ti:sapphire laser-driven HHG in a gas jet versus hollow fibers of different bore diameters (300 μm and 200 μm).
- * To understand the role of electron trajectories and phase-matching conditions in determining harmonic beam quality.
Main Methods:
- * Experimental generation of 19th harmonic beams using a Ti:sapphire laser.
- * Utilizing a gas jet and 10-mm-long hollow fibers with 300 μm and 200 μm bore diameters as HHG media.
- * Measurement of beam quality factor M² for the generated harmonic beams.
Main Results:
- * The 300-μm hollow fiber yielded superior beam quality (lower M²) compared to the gas jet, attributed to phase matching including atomic dipole phase from short trajectories.
- * The 200-μm hollow fiber produced a more divergent beam with a higher M² due to long electron trajectories.
- * Phase-matching within short hollow fibers effectively selects electron trajectories contributing to HHG.
Conclusions:
- * Hollow fibers offer a viable method for improving harmonic beam quality in HHG, with bore diameter being a critical parameter.
- * The choice between gas jets and hollow fibers, and the specific hollow fiber dimensions, depends on the desired balance between harmonic yield and beam quality.
- * Understanding and controlling electron trajectories through phase-matching in hollow fibers is key to optimizing HHG sources.
