This chapter focuses on experimental techniques in the micro/nanoscale thermal radiation. The contents in the chapter are divided into two parts based on either far- or near-field measurement. The contents mainly involve far-field Fourier transform infrared microscopes, near-filed scanning thermal microscopy, and near-field thermal radiation instrument. We will review some outstanding experiments performed by different research groups for measuring the properties of micro/nanoscale thermal radiation. This chapter can be served as a guideline for researchers to design the experimental setups.

These years, we have witnessed great progress in manipulating radiative properties of thermal radiation, including angular, spectral, and polarized responses, via tailoring the light–matter interaction by taking advantages of designed nanostructures, metamaterials or metasurfaces, novel 2D materials, or even anisotropic materials. This chapter will review and give a detailed introduction of several manipulating mechanisms based on different types of materials, giving a comprehensive view of recent progress of radiative property engineering.

This chapter will focus on some important theories in micro/nanoscale thermal radiation, which are the basis of this area and become the fundamentals of other chapters in the books. The contents mainly involve electromagnetic wave theory, fluctuation dissipation theorem, and near-field thermal radiation. Brief derivation, solving the process and analysis method will be presented.

This chapter will cover a variety of methods, especially numerical methods of rigorous coupled-wave analysis and finite-difference time-domain solution. These methods are widely used in solving the problems of the micro/nanoscale thermal radiation. It is important and will give students hands-on experience in numerical simulations.

With the great development of theory, experiment, and manipulation of micro/nanoscale thermal radiation, several advanced applications emerge and show promising prospects in high-efficiency energy harvest/conversion such as angular/spectral selective or wideband absorber, thermophotovoltaics, or heat management implements such as radiative cooling, thermal camouflage, cloaking, and illusion. This chapter will give a brief introduction of these state-of-art technologies on the basis of theory of micro/nanoscale thermal radiation.

In this chapter, a summary of numerical algorithms solving the radiative transfer equation (RTE) is presented. These algorithms could be roughly classified into two categories. The one is ray-tracing methods, including the Zone method, Monte Carlo method, and discrete transfer method. The stochastic approach of Monte Carlo codes is widely used, since its flexible applicability to arbitrary multidimensional configurations. The others are methods based on the discretization of the differential form of RTE, including the spherical harmonics method, discrete ordinates method, and finite volume method.

At micro/nanoscale, the general principles of the thermal radiation are failed to solve or explain the majority of radiative problems or phenomena. This chapter will first point out the limitations and reasons of the general principles of thermal radiation by introducing a typical example. Then, some basic concepts, including the role of energy carriers such as photons, electrons, and phonon will be introduced first, followed by the brief introduction of the corresponding governing equations and the influence mechanism in radiative properties. Next, we would like to give a fundamental framework and chart review from macro- to nanoscalethermal radiation, aiming to make the relation and difference between macro- and nanothermal radiation more distinct. Finally, the development of micro/nanoscale thermal radiation in the last decades will be summarized as well.

The radiative transfer equation (RTE) is the governing equation of radiation propagation in participating media, which plays a central role in the analysis of radiative transfer in gases, semitransparent liquids and solids, porous materials, and particulate media, and is important in many scientific and engineering disciplines. This chapter will give a detailed introduction of the RTE. The microphysical derivation and the physical meaning of the relating quantities will be given. Besides, the relationship between the RTE and Maxwell’s equation will also be discussed and deduced as well, to build a comprehensive understanding of the RTE.

Thermal radiation is a ubiquitous aspect of nature, and this subject has developed for several centuries. In order to build a framework of macroscale thermal radiation, this chapter will give brief introductions of some fundamental theories and definitions of basic concepts of thermal radiation, such as blackbody radiation, radiative interactions at a surface, and radiative exchange between two or more surfaces. Besides, gas radiation as an important direction of thermal radiation will be introduced, including the molecular radiation theory, some gas spectral models, and some useful results in engineering applications.

Macrothermal radiation theory and analysis methods have been widely used in several real applications, such as heat transfer processes in the industrial boiler, radiant heat exchanger design, solar-thermal conversion in solar power plants, and so on. This chapter will cover the applications associated with macrothermal properties control, and some typical application examples will be given, hoping to offer a guidance in engineering applications.