A Novel Integrated Optomechanical Transducer and Its Application in Atomic Force Microscopy

J. Zou, H. Miao, T. Michels, V. Aksyuk
National Institute of Standards and Technology, US

Keywords: MEMS, AFM, atomic force microscopy, nanofabrication, optomechanics, optical resonator

Summary:

Cavity optomechanics studies the coupling of optical and mechanical degrees of freedom in an optical cavity. It has made great progress in recent years and enabled quantum-limited measurement of mechanical motion. One important application is in the field of atomic force microscopy (AFM) where one uses a mechanical cantilever to image the surface of a sample. A proper-designed nanoscale cantilever not only leaves smaller footprints and saves cost, but may also provide higher scanning rates and resolution. However, when the dimensions of the cantilever become comparable or smaller than the optical wavelengths (hundreds of nanometers), traditional optical transduction schemes (e.g. beam deflection and laser interferometry) become ineffective because of diffraction. This prevents the application of the nanoscale cantilevers. Cavity optomechanics overcomes the diffraction limitation as it utilizes the near-field coupling, which is not limited by the wavelength. Combining a high-Q optical cavity and a nanoscale cantilever, we fabricate an integrated optomechanical transducer with a sharp tip overhanging on the chip edge and demonstrate it as an AFM probe working in the contact mode. Besides the benefits aforementioned, the integrated transducer does not require the time-consuming procedure of optical alignment, which is necessary in traditional optical transduction schemes.