Channel waveguides fabricated in 2D photonic crystals of Si nanopillars

Two-dimensional photonic crystal (PC) slabs were fabricated by arranging Si nanopillars into square lattices with period of 490 nm. The fabrication process of nanopillars used iron clusters as nuclei for self-formation of etching masks to obtain high-aspect-ratio structures. The PC slabs were embedded in grooves (1.2 μm deep×200 μm wide×4 mm long), sandwiched between the two silver layers whose refractive index is less than 1 for light confinement. Two kinds of line defects, a missing row of pillars and a reduced-diameter-pillar row, were introduced into the PC. The photonic band gap (PBG) was clearly observed in transmittance spectra for wavelength λ of 900–1000 nm. In the PBG, a sharp peak corresponding to the defect mode was observed at λ=935 nm, which indicates the line defect acted as an optical waveguide.