Subwavelength ripples adjustment based on electron dynamics control by using shaped ultrafast laser pulse trains

Area of Science:

• Materials Science
• Laser Physics
• Surface Science

Background:

• Periodic surface structures, or ripples, are formed on materials by laser irradiation.
• Understanding and controlling ripple formation is crucial for surface modification and nanotechnology.

Purpose of the Study:

• To investigate the influence of designed femtosecond laser pulse trains on the formation and characteristics of periodic surface structures in fused silica.
• To demonstrate the control over ripple periods and orientations by manipulating transient electron dynamics.

Main Methods:

• Irradiation of fused silica with designed femtosecond laser pulse trains.
• Systematic variation of pulse delays (0 to 100 fs) between subpulses.
• Analysis of resulting surface ripple periods, ablation areas, and orientations using microscopy and spectroscopy.

Main Results:

• Femtosecond laser pulse trains enable adjustment of ripple periods from ~550 nm to ~255 nm.
• Ripple orientation can be precisely rotated by up to 90° through pulse delay control.
• Near-wavelength and subwavelength ripple periods correlate with fundamental and second-harmonic wavelengths in fused silica.

Conclusions:

• Designed femtosecond laser pulse trains offer a method to control periodic surface ripple formation in fused silica.
• Transient localized electron dynamics play a significant role in ripple formation and surface morphology.
• This controlled ripple generation has potential applications in advanced material surface engineering.