Enhanced emission with angular confinement from photonic crystals
We consider the emission of dipoles embedded in a photonic crystal. We demonstrate that it is possible to obtain an angular confinement of the emission (i.e., a large coherence area) together with an enhancement of the emitted power. A simple geometrical construction gives us a very comprehensive guideline. We illustrate the developed ideas with a structure working at the band edge of an expanded cubic photonic crystal and we take advantage of the large value of the density of states at these wavelengths. Then, it is shown that both directivity and total emitted power can be improved simultaneously without requiring defect modes.