Observation of leaky slab modes in an air-bridged semiconductor waveguide with a two-dimensional photonic lattice

An air-bridged, 120-nm-thick semiconductor slab with a two-dimensional (2D) square array of through holes on a 480 nm pitch (Λ) was fabricated using selective wet etching techniques. The second order photonic resonances of the structure were studied by comparing broadband optical scattering data with numerical solutions of Maxwell's equations. Features observed in these spectra over a 1200 cm^-1 range, near 9500 cm^-1, indicate that the 2D texture splits the energy degeneracy of slab modes with propagation constants {±2π/Λ,0} and {0,±2π/Λ} by as much as 14%.