Homogeneous layer models for high-spatial-frequency dielectric surface-relief gratings: conical diffraction and...

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Dielectric surface-relief gratings are crucial optical components.
• Accurate modeling of grating behavior is essential for device design.
• High-spatial-frequency gratings present unique modeling challenges.

Purpose of the Study:

• To evaluate the validity of homogeneous layer models for high-spatial-frequency dielectric gratings.
• To assess model accuracy for both nonconical and conical diffraction.
• To utilize validated models for designing antireflecting gratings.

Main Methods:

• Describing gratings as uniaxial material slabs.
• Solving transcendental equations to determine ordinary and extraordinary indices.
• Defining and comparing higher-order, second-order, and first-order indices.
• Employing rigorous coupled-wave analysis for design evaluation and optimization.

Main Results:

• Homogeneous layer models with higher-order and second-order indices demonstrate accuracy for high-spatial-frequency gratings.
• Models remain accurate even at wavelength-to-period ratios near higher-order wave onset.
• Successful design of antireflecting gratings on silicon substrates, including for conical incidence.

Conclusions:

• Homogeneous layer models are reliable for high-spatial-frequency dielectric gratings.
• Validated models facilitate the design of advanced optical elements like antireflecting gratings.
• Rigorous coupled-wave analysis is vital for confirming and optimizing grating designs.