Suspended Dielectric Mirrors at Deep Subwavelength Scale

Reduction in the thickness of air-suspended mirrors to the deep subwavelength scale can facilitate efficient optical and mechanical design. The thinner the mirror, the smaller is its mass, and the more excellent mechanical properties it presents. Thin mirrors are easily displaced by optical radiation pressure, and could present more intense light-mirror interactions than their thicker counterparts. Herein, we present this kind of ultraflat air-suspended mirrors that can reflect light at the telecom region, with a mirror thickness of approximately 25 nm and total thickness of 50 nm. This kind of mirrors shows many unique properties, e.g., the mirrors become increasingly transparent with diminishing film thickness at nonresonant wavelength; there is a strong evanescent field distribution outside the mirrors; the reflection wavelength is almost independent of the refractive index of the mirror materials, and nearly only depends on the lattice geometry at the deep subwavelength scale; moreover, their quality factor significantly improves, which is important for applications in laser, cavity optomechanics, and cavity quantum electrodynamics.