Axion is the dark particle introduced to the quantum chromodynamics to solve the strong CP-problem. Because of its dark nature, there are many indirect evidences, but axion itself have not been registered till now. In the paper, we report the observation of dark axion-like particles formed by the polariton coupling in the resonant microcavity of a globular photonic crystal. To overcome the very small cross-section, we use the Bose-Einstein condensation of polaritons into the nearest-to-the-surface microcavity of an opal-like globular photonic crystal. This way, the synchronicity conditions are met and all polaritons have the same wavefunction to be coupled. Moreover, the giant density of states of a Bose-condensate makes polariton coupling not only allowed but stimulated. At the experiment, we observe “Light Shining through a Wall” Primakoff effect which proves dark particles. The additional spectral peak at the unitary polariton line of a maximal transparency of a crystal allows to differ bipolaritons from other particles. The results can be used not only to generate dark particles at a lab, but also to get a laboratory source of an optical-frequency gravitational waves.
Phase-resolved pulse propagation through metallic photonic crystal slabs: plasmonic slow light
