3. Guides and cavities

The design of integrated devices is based on the engineering of simple or extended structural defects, inducing allowed states in the crystal's band gap. Typical examples are shown in Figure 2 . Depending on the desired goal, their optical behavior in the crystal plane will be studied by coupling these defects together, for example to create more complex filtering functions, or their out-of-plane behavior by introducing the third dimension into the design, whether for the study of cavity emission or the influence of radiation losses on guided propagation.