DNA optomechanics using a photonic cavity-on-tip

Nanoscale strings are unique mechanical structures that span size scales and can be particularly compliant to transverse deformations. This compliance sets them apart from top-down fabricated mechanical structures, providing an ideal platform for realizing nanomechanical force sensors as well as enabling a high level of resonance tunability. There is a storied history of using carbon nanotubes to achieve such unprecedented sensitivities and tunabilities, and in this work, we will discuss our use of DNA strings as new platform in this domain, with an eye towards tailoring the DNA structure using the tools of biology.

In our work, we suspend small DNA bundles over pillar arrays and measure their motion in vacuum with tapered-fiber-coupled nanobeam photonic cavities on a scannable probe tip. The in-situ nature of our probe tip enables us to interrogate multiple DNA molecules, map the cavity field profile, and to study motion in both transverse directions. With our platform, we measure the sub-nm broadband thermal vibration of a tensioned DNA bundle, and demonstrate a strong optical spring effect, tuning the mechanical frequency by over 20% of its bare frequency.