Novel enhancement of interaction between light and matter in confined electron system

In physics, the light wave and the electronic excitation wave have been described in hierarchically different regimes,i.e., the macroscopic (classical) and the microscopic (quantum mechanical) regimes. In this conventional description, no spatial interplay between these waves appears. However, in the recent work, we observed a new class of light-matter coupling in an ultrahigh-quality semiconductor thin film with a couple of hundreds nanometer thickness, wherein these two waves form a harmonized wave-wave coupling over a range of multiple wavelengths. This novel light-matter coupling leads to a great enhancement of the performance of photo-functional materials. For example, the light-matter coupling becomes exceptionally strong and the optical response (radiative decay) time becomes less than one hundred femtoseconds. This response speed is three to four orders of magnitude faster than the typical high-speed radiative decay in nanostructures.
Our results provide a clear example showing that the straightforward control of the size and quality of conventional structured materials can interface hierarchically different (macroscopic and microscopic) spatial degrees of freedom, which considerably enhances the degree of freedom enabling the development of unconventional photo-functions.