Low-loss optical channel drop filters based on high-contrast Si–air photonic crystals by wet anisotropic etching

Abstract

Fiber pigtailed optical channel drop filters based on high-contrast silicon (Si)–air photonic crystals (PCs) have been designed and fabricated. A low fiber-to-fiber insertion loss of 2.2 dB is achieved using lensed fiber pigtails inserted into alignment grooves fabricated along with the filter layers that have smooth vertical sidewalls obtained by the high-aspect-ratio crystallographic orientation-dependent wet anisotropic etching of (110) planar Si wafer. Four filters with varying defect widths have been fabricated to drop wavelengths in the 1520–1603 nm range. It is shown that a 2% to 8% change in the periodicity and the associated change in the filling factor introduced in the constituent PC mirrors leads to large photonic bandgaps.