Cambridge NanoTech Inc.

PHOTONIC CRYSTALS

Static photonic band tuning in a two-dimensional triangular lattice photonic crystal Si slab waveguide has been demonstrated by nanoscale modification of the dielectric contrast using atomic layer deposition of TiO2. For the case of a Si waveguide structure and TiO2 deposition, a tuning range of 12% with a precision of 0.005% has been demonstrated in the optical properties and photonic band structure. Greater control and finer scale tuning can be achieved by depositing a film with a lower refractive index than TiO2. Conversely, a larger range of frequency tuning can be achieved with higher index films, with the tuning precision determined by the deposition rate. It has been demonstrated that adjustments can be made not only to the band frequency but also to the dispersion, enabling precise tuning to achieve a zero group velocity for slow-light applications. The precision and uniform control of this technique enables unprecedented adjustment to the dispersion properties of any 2D photonic crystal. Additionally, by the application of multicomponent ALD, this technique facilitates the formation of layered and composite 2D PC waveguides thus opening new fabrication routes to control dispersion, propagation, and dielectric contrast. Also the technique can be used to add increased functionality and to fabricate active device structures for integration with electronic devices. This capability will enable structures to be tuned for specific purposes, such as beam guiding, dispersion, and slow light control, and may also impact the design of ultralow loss structures.