Radiative transfer in the near field

Summary form only given. The behaviour of systems that are supposed to be very well-known may reveal surprises when we look at them on a nanometric length scale. This is the case of light emission by a body at temperature T. A thermal source such as a blackbody or the incandescent filament of a light bulb is often presented as the typical example of an incoherent source as opposed to a laser. Indeed, whereas a laser is monochromatic and very directional, a thermal source has a broad spectrum and is usually quasi-isotropic. However, it has been shown recently that the field emitted by a thermal source made of a polar material at a distance of the order of 10 to 100 nm is enhanced by more than four orders of magnitude and is partially coherent. The purpose of this paper is to discuss the implications of these effects for the radiative heat transfer between objects separated by distances in the range of the nanometer.