Radiation properties of sources inside photonic crystals
The control of spontaneous emission is an important problem both in basic and applied physics. Two main problems arise in the control of emission: enhancement or suppression and angular confinement of radiation. In this work we studied the properties of emission of radiation from a localized microwave source embedded inside a photonic crystal. We showed that by using a photonic crystal it is possible to enhance the emitted power. We achieved up to 22 times enhancement of power at the band edge of the photonic crystal. We also studied the properties of emission of radiation from a source embedded inside a single defect structure and embedded inside a coupled defect structure. Enhanced emission for single defect and coupled defect structures was also observed. Moreover, angular distribution of power from a localized microwave source embedded inside a photonic crystal was studied. Angular confinement was achieved near the band edge of the photonic crystal. Half power beam widths as small as 6 degrees were obtained. This is the smallest half power beam width in the literature obtained by using photonic crystals. We also investigated frequency and size dependence of the angular distribution. We observed that the angular confinement strongly depends on frequency and on the size of the photonic crystal. In fact, we showed that angular confinement could be obtained just at the band edge frequency. In conclusion, our work showed that the problem of controlling the spontaneous emission could be solved at once by using photonic crystals.