Controlling the speed of light

Interesting phenomena of photonic crystals (PhCs), like bandgaps and waveguiding, have lead to a tremendous increase of research interest in this area. High-end functionalities in electro-optical circuts urge to optimize these structures. So far mostly trial and error methods have been applied to improve the behaviour of the PhCs components, like, e.g., to maximize the bandgap of PhCs or to reduce the losses of waveguides in PhCs. Recently also topology optimization was applied to synthesize, e.g., high transmission waveguide bends and junctions. In this work we extend the topology optimization method to not only to create a bandgap around an a-priorily chosen guided mode, but also to control it's group-velocity under the light-line.