Controlling Radiative Decay Rates with Magnetic Metamaterials

Metamaterials are man-made composites which have been found to have exotic and interesting optical properties, such as negative refractive indices and invisibility cloaking. Actually, a lot of these properties come from the fact that these materials take parts in artificial magnetism. While the magnetic responses of conventional atomic and molecular media are too weak to be considered at the infrared and at the visible frequencies, metamaterials provide an effective route to create stronger magnetic responses at these frequencies. It also becomes interesting to ask whether the artificial magnetic response can have an influence back on the atomic dipole transitions including both the electric and the magnetic ones. Unlike using the conventional structures such as photonic crystals and common plasmonic structures without magnetic response, this will add an extra dimensionality in controlling the radiative decay rates. In this project, we are interested to use artificial magnetic metamaterials to control both electric and magnetic dipole transitions near optical frequencies. Such an approach has remained not much explored except for some simple structures like a metallic mirror or a nanoparticle. We need to first develop the corresponding theoretical and three-dimensional simulation tools in order to study the radiative decay rates with metamaterials. We will study the response of the metamaterials regarding the radiative decay rates at different levels of complexity, ranging from the individual artificial atoms to the whole metamaterial and the corresponding effective medium description. Such investigations will allow us to understand the interaction between the light, the metamaterials and the atom placed near or inside the metamaterials. To the end, these will help us to design realistic threedimensional magnetic metamaterials that can be used to enhance the magnetic dipole transitions and to suppress the electric dipole transitions at the same time. As metamaterials have already been proven to be very useful in dispersion engineering , subwavelength focusing and transformation optics, the same should also apply to the control of the photon density of states and hence the radiative decay rates which will be useful in considering processes like spontaneous emission and photoluminescence. These investigations will not only expose the interesting physics of magnetic metamaterials in controlling radiative decay rates but will also be important to develop future experiments and designs of many quantum optical devices, such as efficient light sources and sensitive magnetic probes.