Nowadays, all optical devices based on nonlinear effects acquire a great importance in optical communications systems
and photonic processing. Particularly relevant are the devices that use low-level power pumping in the generation of
those effects. These optical devices can be implemented by means of different structures and materials. One of the most
significant structure, here described and presented, is the semiconductor semimagnetic microcavity, composed by a
Fabry-Perot microcavity with a semiconductor semimagnetic material and a quantum well in the middle. Inside these
media nonlinear effects such as four wave mixing and magneto-optical polarisation rotations can be observed and
utilised for developing optical amplifiers, wavelength converters and nonlinear magneto-optical based devices. In order
to reduce the pumping power needed for obtaining nonlinear effects new structures with different materials can be built.
For instance, Fabry-Perot vertical microcavities, whispering gallery based microcavities or hybrid system of photonic
crystal microcavities can improve their performance and so make possible a real implementation. A key point in the
design of such micro-resonators is the election of the appropriate material inside. A study of the influence of several
materials, with a high dispersion and able to provoke electromagnetically induced transparency is, also, presented. The
changes of the quality factor of these nonlinear micro-resonators are analysed. Potential applications for optical
computing are shown.