Modeling Spontaneous Emission Control in Photonic Crystals by Ferromagnetic Resonance

The radiation dynamics of a magnetic dipole located inside a photonic crystal has been considered as an analogue for optical emission of a point-like emitter in such a crystal. We have experimentally realized this situation by fixing a single crystal yttrium iron garnet (YIG) sphere of 1.7 mm diameter inside a photonic crystal consisting of dielectric alumina rods. These rods form a woodpile structure of size 16 × 6 × 6 cm³ . The photonic crystal shows a band gap at microwave frequencies between 12.9 and 14.3 GHz as calculated and verified from the transmission characteristics of the crystal. The radiation feedback of the YIG sphere was probed by ferromagnetic resonance experiments covering a large frequency range from 8 to 17 GHz. Whereas outside the band gap the radiation-induced linewidth amounts up to 30 Oe, it is almost completely suppressed inside the gap. From the full analysis of linewidth and resonance shift, we could clearly prove the non-Markovian character of the radiation dynamics at the edges of the gap as expected from theory. The experimental control of spontaneous emission, as realized in our experiment, is a very promising step towards future optical applications in low threshold lasers, highly efficient light emitting diodes or photovoltaic solar modules.