Broadband extreme ultraviolet dispersion measurements using a high-harmonic source

Area of Science:

• Optics and Photonics
• Materials Science
• Ultrafast Spectroscopy

Background:

• Accurate characterization of thin film optical properties is crucial for advanced optical devices.
• Traditional methods for dispersion measurement at extreme ultraviolet (EUV) wavelengths are often complex and require specialized equipment.

Purpose of the Study:

• To demonstrate a novel, table-top method for direct dispersion measurements of thin films at EUV wavelengths.
• To provide a versatile technique applicable to a wide range of materials.

Main Methods:

• Utilizing a laser-driven high-harmonic generation (HHG) source to produce identical, spatially separated EUV pulses.
• Employing a single toroidal mirror for re-imaging and a reference aperture.
• Comparing EUV interference patterns with and without the thin film sample to extract dispersion information.

Main Results:

• Successfully measured the dispersion properties of titanium, nickel, copper, and silicon nitride thin films.
• Demonstrated the technique's applicability to materials with sufficient EUV transmission.
• Validated the method for integrated dispersion measurement over the full film thickness.

Conclusions:

• The developed HHG-based method offers a direct and accessible approach for EUV dispersion measurements.
• This technique advances the characterization of thin films for applications in EUV optics and nanophotonics.
• The versatility across multiple materials highlights its potential for broad scientific and industrial use.