In the last decades, designs of most incandescent sources have been realized by heating the whole device. Here we propose a novel approach consisting in taking advantage of hot nanoemitters that can be cooled in a few tens of nanoseconds. It offers a new opportunity for high speed modulation and for enhanced agility in the active control of polarization, direction and wavelength of emission. To compensate the weak thermal emission of isolated nanoemitters, we propose to insert them in some complex environments, such as e.g. the gap of cold nanoantenna, which allow a significant thermal emission enhancement of the hot nanovolume. In order to optimize this kind of device, a fully vectorial upper bound for the thermal emission of a hot nanoparticle in a cold environment is derived. This criterion is very general since it is equivalent to an absorption cross-section upper bound for the nanoparticle. Moreover, it is an intrinsic characteristic of the environment regardless of the nanoparticle, so it allows to decouple the design of the environment from the one of the hot nanovolume. It thus provides a good figure of merit to compare the ability of different systems to enhance thermal emission of hot nanoemitters.
Currently, there are no cheap and compact sources in the mid-infrared range that can be modulated at high frequencies. While hot membranes are common IR sources, their thermal inertia limit the modulation rates to a few tens of Hertz. Moreover, available thermal sources are unpolarized, isotropic, broadband and have a low efficiency. However, there is no fundamental limit that imposes these properties. It turns out that they can be strongly modified by using appropriate nanostructures. In this presentation, we report the design, fabrication and characterization of infrared incandescent sources, modulated faster than 10 MHz with a controlled spectrum and polarization.