Mesoscopic optics

We introduce Mesoscopic Optics as a fundamentally new direction of research and innovation. Micro-nano-integration is central and at the heart of establishing this field. It will give access to previously unknown potential that can be harvested, e.g., in form of optical applications. The central starting point is thereby the strategy 'not smaller than necessary', rather than the often practiced 'as small as possible'. The building elements are mesoscopic optical devices such as optical microcavities. They are governed by the laws of mesoscopic physics that are relevant for the description of objects with typical dimensions in the micrometer scale. The fact that the relevant wavelengths are of the order of the system size implies a use of both a wave and a ray description of the system, and to relate them by the principle of ray-wave correspondence. Deviations between the two pictures arise typical from the onset of interference effects in small, coherent systems. They open the possibility to control and manipulate the system behaviour via the control of semiclassical corrections and geometric phases.