Authors: E.M. Yeatman and A. Lipson
Affilation: Imperial College London, United Kingdom
Pages: 409 - 412
Keywords: photonic bandgap, tuneable filters, anisotropic etching
Photonic Bandgap (PBG) devices have been widely investigated because of their capabilities for manipulating light within highly constrained dimensions. Many PBG devices have been fabricated in III-V semiconductors to take advantage of their active optoelectronic properties. However, high scattering losses, resulting from poor surface quality, have typically resulted in unacceptable performance. We have explored silicon as an alternative PBG material, since far higher etched surface quality is achievable as a result of the quality of the crystalline material, and the better etch processes available. We have fabricated spectral filters using 1-D PBG cavities. Deep reactive ion etching (DRIE) allows projection of the photolithographic pattern into the substrate with high aspect ratio. Using (110) oriented wafers with vertical (111) planes, and following the DRIE step with a short anisotropic wet chemical etch, we polish the critical (111) surfaces to atomic precision. By this approach, we have obtained near-ideal filter bandwidth, as well as low insertion loss. Electrostatic MEMS actuation is included for tuning. This paper will explore the analysis and modelling of the structures, the nano-scale characterisation challenges, and the application possibilities for silicon PBG devices in optical sensing and signal processing.