Nonpolarizing guided-mode resonant grating filter for oblique incidence

Area of Science:

• Optics and Photonics
• Nanophotonics
• Diffractive Optics

Background:

• Polarization dependence is a significant challenge in optical filter design, particularly for applications involving oblique incidence.
• Guided-mode resonant grating filters offer potential for compact and efficient optical filtering.
• Existing designs often struggle with polarization sensitivity, limiting their practical use.

Purpose of the Study:

• To introduce a new type of guided-mode resonant grating filter.
• To achieve polarization independence for oblique incidence.
• To explore the suitability of specific grating structures for enhanced performance.

Main Methods:

• Theoretical analysis of light-wave interaction with grating structures.
• Numerical calculations employing two-dimensional rigorous coupled-wave analysis (2D-RCWA).
• Design and simulation of a crossed grating structure with a rhombic lattice.

Main Results:

• Demonstrated polarization independence for oblique incidence.
• Identified a rhombic lattice structure as suitable for guided-mode resonant grating filters.
• Showcased a configuration where incident light is diffracted into two perpendicular propagation modes within the waveguide, achieving a fill factor of approximately 50% at a 45-degree incident angle.

Conclusions:

• The proposed guided-mode resonant grating filter design overcomes polarization sensitivity issues.
• The rhombic lattice structure and specific mode configuration are key to achieving high performance.
• Numerical estimations indicate acceptable tolerances for setting and fabrication errors, paving the way for practical implementation.