Fabrication and simulation of diffractive optical elements with superimposed antireflection subwavelength gratings

Area of Science:

• Optics and Photonics
• Nanotechnology
• Materials Science

Background:

• Blazed gratings are essential optical components but can suffer from surface reflections and limited diffraction efficiency.
• Subwavelength structures offer unique optical properties for manipulating light.
• Combining different grating types can lead to synergistic performance enhancements.

Purpose of the Study:

• To investigate the superposition of subwavelength phase gratings onto blazed phase gratings.
• To enhance diffraction efficiency and reduce surface reflections.
• To compare the optical performance of bare blazed gratings with those carrying subwavelength gratings.

Main Methods:

• Fabrication of bare blazed gratings and blazed gratings with superimposed subwavelength gratings using direct-write electron-beam lithography.
• Experimental characterization of optical performance, focusing on diffraction efficiency for TE polarization.
• Simulation of experimental results using rigorous diffraction theory.

Main Results:

• Subwavelength-carrying gratings achieved a maximum diffraction efficiency of 90.6% for TE polarization.
• Bare blazed gratings exhibited a maximum diffraction efficiency of 86.3% for TE polarization.
• The experimental results were validated through rigorous diffraction theory simulations.

Conclusions:

• Superposition of subwavelength gratings onto blazed gratings is an effective method to increase diffraction efficiency.
• This technique offers a pathway to improved optical component performance.
• The findings are supported by theoretical simulations, confirming the enhanced optical properties.