Broadband mirrors for surface plasmon polaritons using integrated high-contrast diffraction gratings.

Area of Science:

• Photonics and Nanotechnology
• Plasmonics
• Optical Metamaterials

Background:

• Surface plasmon polaritons (SPPs) are electromagnetic waves confined to metal-dielectric interfaces.
• Controlling SPP propagation is crucial for developing integrated optical circuits.
• Existing methods for SPP manipulation often lack broadband efficiency or require large footprints.

Purpose of the Study:

• To propose and numerically investigate integrated high-contrast gratings (HCGs) for SPP manipulation.
• To demonstrate the potential of HCGs as broadband plasmonic mirrors.
• To explore methods for enhancing HCG efficiency and practical feasibility.

Main Methods:

• Numerical investigation of HCGs composed of silicon pillars on a gold surface.
• Analysis of SPP reflectance for both normal and oblique incidence.
• Implementation of a parasitic scattering suppression technique using two-layer grating pillars.

Main Results:

• HCGs function as broadband plasmonic mirrors with mean reflectance exceeding 85% over a 200-nm spectral range.
• The HCGs exhibit a subwavelength footprint in the SPP propagation direction.
• A two-layer grating pillar design effectively suppresses parasitic scattering and enhances efficiency.

Conclusions:

• Integrated HCGs offer a promising solution for efficient broadband SPP reflection.
• These HCGs are suitable for on-chip integration due to their compact size.
• The developed HCGs can be utilized in two-dimensional optical circuits for precise SPP steering.