Multiple-channel guided mode resonance Brewster filter with controllable spectral separation.

Area of Science:

• Photonics and Optical Engineering
• Nanophotonics
• Waveguide Optics

Background:

• Guided Mode Resonance (GMR) filters are crucial optical components.
• Traditional GMR filters often have material-dependent resonance locations.
• Controlling spectral separation in GMR filters is a key challenge.

Purpose of the Study:

• To propose a single-layer, multiple-channel GMR Brewster filter.
• To demonstrate controllable spectral separation using the fill ratio.
• To analyze the relationship between fill ratio and spectral characteristics.

Main Methods:

• Utilized the plane waveguide method for theoretical analysis.
• Employed rigorous coupled-wave analysis (RCWA) for simulations.
• Analyzed the normalized eigenvalue equation to understand spectral control.

Main Results:

• The spectral separation of resonances is controllable by modifying the grating fill ratio.
• Resonance location and separation can be precisely tuned via fill ratio adjustments.
• Achieved a maximal shift of 5% for the second resonance relative to the first.

Conclusions:

• The proposed GMR Brewster filter offers tunable spectral separation independent of material properties.
• Fill ratio modification provides a linear and controllable method for spectral tuning.
• This approach enhances the design flexibility of GMR-based optical filters.