In this work, we studied variations of the spontaneous emission rate of internal sources used as probes of variations of the local photonic density of states. Materials as diverse as polymers or inorganic disordered media, photonic crystals and plasmonic nanostructures were characterized. Thus, we discuss successively i) changes of spontaneous emission rate of internal sources due to local density variations of the surrounding polymer medium, both below and above the glass transition temperature; ii) changes of the spontaneous emission rate as a result of conformational changes of fluorescent molecules due to movements of surrounding chains, iii) the study of the fluorescence inhibition /exaltation in photonic crystals and iv) the emission in plasmonic nanostructures. Finally, we describe some research perspectives such as i) the development of highly disordered materials to study the phenomena of light localization and random lasers; ii) the development of plasmonic nanostructures combining localized and propagating surface plasmons to generate high Purcell factors in a spectral range either very wide or very narrow and iii) the development of plasmonic structures sensitive to the optical Kerr effect to achieve optical bistables.
