Silicon micromachined periodic structures for optical applications at λ=1.55 μm

In this letter, the authors report the design, fabrication, and characterization of a silicon micromachined periodic structure for optical applications at λ_c=1.55 μm. The microstructure, which can be envisioned as a one-dimensional photonic crystal, is composed of a periodic array of 1-μm-thick silicon walls and 2-μm-wide air gaps, each one corresponding to a different odd number of quarter wavelength at λ_c (hybrid quarter wavelength). The fabrication is based on the electrochemical etching of silicon, yielding parallel trenches with depths up to 100 μm. Preliminary reflectivity measurements show the presence of a band gap at λ_c=1.55 μm, as theoretically expected.