Two-Dimensional Photonic Crystals Fabricated in Monolithic Single-Crystal Silicon

We describe the fabrication of photonic crystals (PCs) in monolithic single-crystal Si on standard wafers without the need for silicon-on-insulator materials, and we demonstrate two types of PC devices based on this technology. The first is a PC mirror that exhibits broadband high reflectivity in the telecommunication wavelength band (> 90% from 1420 to 1520 nm). The second device shows large changes in reflectivity over narrow wavelength regions and has a sharp (3.5 nm wide) reflection minimum around 1550 nm, making the PC well suited for sensor applications. In both types of PC devices, guided resonances in the PC slab are exploited to obtain the desired reflection response. The PCs are fabricated in a process consisting of a series of oxidation and etch steps, with only one initial lithographic mask. The resulting PC slabs are monolithic structures, with the advantages of very thin and flat membranes with low internal stress, no temperature expansion coefficient mismatch, and compatibility with microelectromechanical systems and complementary metal-oxide-semiconductor processing.