Polarization reflection analysis of a binary phase grating filter on an ellipsoidal collector

Area of Science:

• Optics and Photonics
• Plasma Physics
• Materials Science

Background:

• Laser-produced plasma (LPP) sources require efficient infrared (IR) wavelength suppression for optimal performance.
• Binary phase gratings are essential components for managing radiation in advanced illumination and imaging systems.
• Polarization-dependent behavior of gratings impacts IR suppression efficiency.

Purpose of the Study:

• To systematically investigate the polarization properties of binary phase gratings on ellipsoidal collectors in LPP light sources.
• To analyze and optimize IR suppression efficiency for high-power EUV and X-ray applications.
• To develop a novel model for understanding p-polarized IR reflectance characteristics.

Main Methods:

• Finite Element Method (FEM) and Fourier optics simulations with the thin-element approximation (TEA).
• Analysis of diffraction behaviors for s- and p-polarized IR light at large incidence angles.
• Experimental validation of simulation results and IR suppression levels.

Main Results:

• Binary phase gratings achieve high IR suppression ratios (up to 10^-4).
• Significant differences in diffraction behavior observed between s- and p-polarized IR light.
• P-polarized IR light demonstrates lower 0th-order reflectance compared to s-polarized light.

Conclusions:

• Adjusted grating depths are critical for optimizing IR suppression at large incidence angles.
• A novel 'turned wave' model provides insights into p-polarized reflectance oscillations.
• The developed grating technology is suitable for practical applications, considering fabrication tolerances and spectral linewidth.