Passive waveguide device technologies — Building block of functionality and integration

Any function can be realized by passive waveguide devices, without emission and detection. Appropriate selection of device structure and material is needed, because optical functional devices are not the digital circuit but analogue devices. Integration is a natural consequence of the requirements of functionality, less connection points, compactness and stabilization. Appropriate selection of building blocks and technology is needed, together with a new approach and material (silicon photonics, InP-based photonics or something else?).