A new photonic atom: Submicron silicon nanocavities with strong magnetic resonances in the optical region

The essence of electronic binding lies in the electromagnetic force resulting from the exchange of virtual photons. This constitutes the basis of chemistry. Similar effects appear in neighboring optical microcavities when shined with a laser beam. Following this analogy, the optical modes of a microcavity resemble to the electronic orbitals of an atom, then called photonic atom (PA). The photonic interaction of several PAs may form photonic molecules (PM). The PM concept, has allowed studying new properties of light-matter interaction. Also it has been applied to realize low threshold microlasers, enhanced directional light emission, high sensitivity sensors and even quantum information processes. The most typical examples of PAs range metallic nanoparticles, to low refractive index dielectric microspheres or microdisks. In the former case (metallic PAs), the high optical dissipation of metals is a big obstacle for developing devices. In the case of low refractive index PAs the whispering gallery modes (WGM) contributing to photonic binding are always localized at the cavity surface, so they would be equivalent to atoms excited into high-energy orbitals. Furthermore, as it happens for electronic orbitals, the electrical resonances of photonic PAs and PMs play a dominant role over the magnetic ones. Here, we show our recent experimental and theoretical results concerning: A) The optical properties of spherical nanocavities made of silicon in the submicron range. B) The strong interaction between silicon colloidal and its mirror image under perfect electric conductor.