A photonic probe for atomic force microscopy includes: a cantilever including: a tip; a wing in mechanical communication with the tip; an extension interposed between the tip and the wing to synchronously communicate motion of the tip with the wing; an optical resonator disposed proximate to the cantilever and that: receives input light; and produces output light, such that: the cantilever is spaced by a gap distance from the optical resonator, wherein the gap distance varies as the cantilever moves relative to the optical resonator, and the output light differs from the input light in response to movement of the cantilever relative to the optical resonator; an optical waveguide in optical communication with the optical resonator and that: provides the input light to the optical resonator; and receives the output light from the optical resonator.
Atomic force microscopy probes with integrated photonic optomechanical cavity readout are new and provide improved sensitivity, increased measurement speed and reduced measurement noise in a variety of research and manufacturing metrology applications. While such probes have been recently demonstrated, they have not been commercialized. Commercialization, as well as further performance improvement by reducing the mechanical and photonic element size, are currently hindered by difficulty of manufacturing of the present probes designs, and specifically by the demanding tolerances for precise undercutting of the substrate edge to expose the probe tip, yet mechanically anchor the center of the microdisk optical cavity. NIST has solved this problem by incorporating the cavity at the end of a larger microfabricated cantilever extending over the substrate edge. Photonic crystal cavities are particularly suitable because in contrast with previously used microdisk cavities, they can be supported by their side(s) without loss of optical quality and are therefore much easier to form at the ends of cantilevers.
Because adding the cantilever relaxes the required accuracy of the substrate edge micromachining, the novel probes can be batch microfabricated with known micromachining techniques suitable to economic mass production.
The benefits of this technology are: nanoscale AFM cantilever interacts with sample; precise measurement of nano-cantilever motion; optical cavity waveguide-coupled to fibers for interrogation; and microdisk cavity.