Applied Digital Optics: From Micro-optics to Nanophotonics

7

Hybrid Digital Optics

7.1 Why Combine Different Optical Elements?

Combining different optical elements in different implementations might at first sight be a ubiquitous task, since optics with similar physical implementation might work better together than hybrid optics. There are three main reasons to do so:

• First, improvement of existing functionalities of standard optics when introducing other optical elements and mixing them in a single system. The first section of this chapter will review such elements, which are mainly hybrid refractive/diffractive elements. These will be labeled ‘elements’.
• Second, the generation of new optical functionalities that cannot be implemented with a single optical element, or multiplexed optical elements. Such elements are not simply spatially multiplexed but, rather, integrated together to produce the new functionality. Such typical elements are integrated waveguide gratings.
• Third and last, but not least, if no optical functionality is to be optimized or even generated, the reduction of the size, weight or cost of a given optical system by hybridizing various optical elements. The planar optical bench is one such example. Chapter 16 provides many more examples.

As most of these hybrid examples are linked to imaging systems [1–3], the various aberrations, expressed for thin lenses, diffractive surface-relief lenses and holographic lenses, will be reviewed. The various functionality enhancement applications using hybrid refractive/diffractive ...