Abstract : This thesis uses whispering gallery modes of optical microcavities. They result from total internal reflexion guidance and exibit very high quality factor and small mode volume. As a first step, this manuscript gives theoretical descriptions of silica microsphere and microtoroid modes. Then, their fabrication is presented. Some improvements, such as the production of sub-20 μm diameter spheres and the use of circular polarization to improve the symmetry of the toroid, are described. We present an in-depth study of their excitation by the taper coupler. We put the stress on the evanescent wave interference phenomenon occurring in the gap. This is responsible for resonance broadening and shifts I study theoretically and experimentally. The previous approach leads to a very powerful technique to determine the radial order. We observe also unexpected resonance lineshapes resulting in coupler modes interferences by analogy with a Mach-Zehnder interferometer. Finally, we raise the issue of Silicon nanocrystal (Si-nc) based microsource using these resonators. The emitters have a controlled size ranging from 0.6 to 6 nm. The CO2 laser reflow activates the Si-nc photoluminescence around 750 nm, but leads to coalescence of the material and a partial destruction. The optical filling factor and the defects in the matrix seem to be the main limitations for significant improvement of the performances. It has been possible to collect the emission from Si-nc coupled with microtoroids in the near and far fields.