Confining light to the smallest possible volume has been a long-standing challenge for researchers. First, because it contributes to the understanding of optics and of how light behaves. Second, because confining light “concentrates” it – it makes light interact much more strongly with matter than it would otherwise. This accelerates various emission\absorption processes, with potential applications ranging from quantum computing to chemical sensing. In its extreme, strongly confined light can completely hybridize with matter (atoms, molecules) and create new phases of matter which do not exist otherwise.
However, so far, the quest to make smaller and smaller cavities has also faced a fundamental limitation – powerful optical absorption that occurs on the nanoscale and dramatically reduces cavity performance. Various approaches have been considered by researchers to reduce to size of cavities without increasing absorption, but so far it has not been possible to create cavities that are simultaneously small and high performing. Succeeding to do so is an important step towards realizing new applications and new and fundamentally interesting states of matter.