RT Journal Article SR Electronic T1 Experimental realization of deep-subwavelength confinement in dielectric optical resonators JF Science Advances JO Sci Adv FD American Association for the Advancement of Science SP eaat2355 DO 10.1126/sciadv.aat2355 VO 4 IS 8 A1 Hu, Shuren A1 Khater, Marwan A1 Salas-Montiel, Rafael A1 Kratschmer, Ernst A1 Engelmann, Sebastian A1 Green, William M. J. A1 Weiss, Sharon M. YR 2018 UL http://advances.sciencemag.org/content/4/8/eaat2355.abstract AB The ability to highly localize light with strong electric field enhancement is critical for enabling higher-efficiency solar cells, light sources, and modulators. While deep-subwavelength modes can be realized with plasmonic resonators, large losses in these metal structures preclude most practical applications. We developed an alternative approach to achieving subwavelength localization of the electric and displacement fields that is not accompanied by inhibitive losses. We experimentally demonstrate a dielectric bowtie photonic crystal structure that supports mode volumes commensurate with plasmonic elements and quality factors that reveal ultralow losses. Our approach opens the door to the extremely strong light-matter interaction regime with, simultaneously incorporating both an ultralow mode volume and an ultrahigh quality factor, that had remained elusive in optical resonators.