On-chip natural assembly of silicon photonic bandgap crystals
Original Entry: Ian Bruce Burgess Fall 2009
1. Y.A. Vlasov, X.-Z. Bo, J.C. Sturm, D.J. Norris, Nature 414, 289-293 (2001).
2. A. Blanco et al., Nature 405, 437-440 (2000).
This paper describes the fabrication of a silicon 3D photonic crystal with sufficiently low defect densities to maintain the complete bandgap over a large volume. The structure is fabricated by infiltrating a thin-layer silica colloidal crystal with Si by low pressure chemical vapor deposition, and then removing the template of the colloidal crystal using buffered oxide etching. This additional step is required to achieve the refractive index contrast required for a complete 3D bandgap (>2.8:1). What allows improved crystal quality in the colloidal opals over previous work , is the use of the meniscus-driven vertical deposition technique as opposed to gravitationally-driven sedimentation. The figure below shows the colloidal crystal (left) and the inverted Si photonic crystal (right).
The photonic crystals were characterized by optical reflection spectroscopy in both the  and  directions. A region of 100% reflection was observed in both directions, confirming the prediction from modeling of an omnidirectional bandgap.