Near-complete absorption of intense, ultrashort laser light by sub-lambda gratings

Area of Science:

• Plasma physics
• Laser-matter interaction
• Nanophotonics

Background:

• Dense plasmas are crucial for various applications, including inertial confinement fusion and X-ray generation.
• Efficient light absorption by plasmas is key to maximizing energy coupling and subsequent processes.
• Surface structures can modify laser-plasma interactions, but their efficacy at extreme conditions requires further investigation.

Purpose of the Study:

• To demonstrate near-100% light absorption in dense plasmas using periodic sub-wavelength structures.
• To investigate the role of structure-induced surface plasmon resonance (SPR) in enhancing light absorption and X-ray emission.
• To validate experimental findings with theoretical models and simulations at record laser intensities.

Main Methods:

• Creation of dense plasmas on solid surfaces featuring periodic sub-wavelength structures.
• Systematic, correlated measurements of light absorption and X-ray emission.
• Testing at high laser intensities (up to 3 x 10^15 W cm^-2).
• Utilizing an analytical grating model and 2D particle-in-cell (PIC) simulations.

Main Results:

• Achieved near-100% light absorption in structured plasmas.
• Observed significantly increased X-ray emission correlated with enhanced absorption.
• Confirmed the crucial role of surface plasmon resonance in driving these enhancements.
• Validated experimental results with theoretical models and PIC simulations.

Conclusions:

• Periodic sub-wavelength structures are highly effective in enhancing light absorption in dense plasmas.
• Surface plasmon resonance is the primary mechanism responsible for the observed absorption enhancement.
• The findings provide a quantitative understanding and a clear pathway for optimizing laser-plasma absorption for applications requiring efficient energy coupling and X-ray generation.