Thermal Effects in Nano Optics

Thermal nearfield radiation and optical forces at the nanoscale have received considerable interest in recent years. Despite the importance of the topic, in this book we only provide a brief introduction and refer the interested reader to the rich literature on the subject. In Chap. 4 we have seen that electromagnetic fields transport energy and momentum, as described by the flow of the Poynting vector and Maxwell’s stress tensor. Similarly, in thermal equilibrium energy and momentum can be transported through field fluctuations, which give rise to effects such as heat transfer or Casimir and Casimir–Polder forces. The systems we have in mind consist of one or several dielectric or metallic bodies, in the following synonymously referred to as absorbing bodies or materials, which are in thermal equilibrium. Alternatively, we will also consider quantum emitters, such as molecules or quantum dots, that interact with these absorbing bodies. The theoretical description within the so-called field of fluctuational electrodynamics combines several concepts discussed in previous chapters, and builds on a linear-response relation between the electromagnetic field operators and the current noise operators of the absorbing materials.