Binary zero-order diffractive and anti-reflective optical elements in silicon for the mid-infrared

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• High-index interfaces often suffer from significant Fresnel reflections, limiting optical system efficiency.
• Diffractive optical elements (DOEs) offer versatile light manipulation capabilities.
• Existing DOEs may not adequately address reflectivity issues in high-index materials.

Purpose of the Study:

• To propose a novel method for designing binary two-level diffractive optical elements.
• To achieve efficient diffractive functionality concurrently with reduced interface reflectivity.
• To demonstrate the applicability of the method in the mid-infrared spectral range.

Main Methods:

• Design of zero-order transmission gratings utilizing subwavelength microstructures.
• Fabrication of the proposed diffractive optical elements using a single patterning step.
• Realization and characterization of a Dammann grating in silicon.

Main Results:

• The developed diffractive optical elements exhibit efficient diffractive performance.
• The proposed structures effectively reduce reflectivity at high-index interfaces.
• Successful fabrication and characterization of a silicon Dammann grating in the mid-infrared spectrum were achieved.

Conclusions:

• The novel method provides an effective approach for designing efficient diffractive optical elements with reduced reflectivity.
• The subwavelength microstructure-based grating concept is suitable for mid-infrared applications.
• Single-step fabrication offers a practical advantage for realizing these optical components.