Surface modes in two-dimensional photonic crystal slabs with a flat dielectric margin

Area of Science:

• Photonics and optical engineering
• Condensed matter physics
• Materials science

Background:

• Photonic crystal slabs offer unique light manipulation properties.
• Surface modes within photonic band gaps are crucial for integrated optics.
• High-index-contrast materials enable compact photonic devices.

Purpose of the Study:

• To numerically simulate and characterize surface modes in 2D high-index-contrast photonic crystal slabs.
• To investigate the dispersion properties and transmission characteristics of these surface modes.
• To explore the sensing capabilities and potential applications of surface modes, such as in optical couplers.

Main Methods:

• Numerical simulations using the plane wave expansion method for band structure calculations.
• Finite-difference time-domain (FDTD) method for analyzing finite-length waveguide modes.
• Spatial Fourier transform for verifying surface mode dispersion curves.

Main Results:

• Multiple surface guided modes were identified within the photonic band gap.
• High-order modes exhibited relatively flat dispersion curves.
• Small changes in ambient refractive index (5 x 10(-3)) induced wavelength shifts of approximately 1 nm for lower-order modes.
• A 4-port, 3-channel bidirectional coupler was designed utilizing a multimode surface waveguide.

Conclusions:

• The study confirms the existence and properties of surface modes in 2D photonic crystal slabs.
• Surface modes demonstrate sensitivity to environmental refractive index changes, suitable for sensing applications.
• The designed coupler showcases the practical application of these surface waveguides in integrated photonic circuits.