Flat-top narrowband filters enabled by guided-mode resonance in two-level waveguides

Area of Science:

• Optics and Photonics
• Nanotechnology
• Materials Science

Background:

• Resonant nanogratings and periodic metasurfaces exhibit tunable spectral and polarization properties.
• Cooperative resonance interactions can shape optical spectra for specific applications, offering an alternative to traditional multilayer dielectric mirrors.

Purpose of the Study:

• To design and theoretically demonstrate guided-mode resonance filters with flat-top spectra.
• To achieve high-efficiency spectral shaping suitable for wavelength division multiplexing (WDM) systems.

Main Methods:

• Utilizing a single one-dimensional grating layer sandwiched between two waveguides.
• Inducing simultaneous, nearly degenerate resonant modes to create the flat-top spectral response.
• Theoretically analyzing the device architecture in the near-infrared region.

Main Results:

• Achieved high-efficiency flat-top spectra in the near-infrared region.
• Demonstrated that resonance separation precisely controls the width of the flat-top spectrum.
• Showcased the ability to implement spectral widths from sub-nanometer to several nanometers with the same device architecture.

Conclusions:

• Guided-mode resonance filters with flat-top spectra are feasible for WDM systems.
• The proposed single-layer grating structure offers a versatile platform for tailored spectral filtering.
• This approach provides a pathway to precisely control spectral bandwidths for optical communication applications.