As we saw in the historical introduction, optics is a field with a long and rich history, through which dozens of generations of scientists and engineers have passed, each contributing a little more to the understanding of and creative uses for light. As scientific and engineering developments have made the micro and nano worlds more accessible, new aspects of optics have come to light; nano-optics is thus a field whose physics and applications have only begun to be appreciated, but which has considerable promise for novel and still unknown science and engineering.

We conclude this text with a look at several aspects of micro-optics that employ nanometer-scale structures to achieve new forms of functionality. The nano-optics field profits from an extensive overlap of developments in basic physics, particularly quantum optics, classical and micro-optics, and advanced fabrication technology. In contrast to mainstream nanotechnology, the prefix “nano” for optics does not necessarily always imply the use of structures at nanometer-size scales, for which smaller is always better; the designation is frequently employed for optical systems with feature sizes smaller than the wavelength, sometimes thus also referred to as subwavelength optics. We consider here micro- and nano-optical concepts with size scales ranging from about a micrometer to a few nanometers; we will focus on devices rather than on fundamental physical effects, of which there is nevertheless a rich variety.