Wide Stiffness Range Cavity Optomechanical Sensors for Atomic Force Microscopy

TL;DR

This paper presents a compact cavity optomechanical sensor capable of high displacement sensitivity across a wide range of cantilever stiffnesses, enabling versatile applications in atomic force microscopy from soft biological samples to high-resolution imaging.

Contribution

The development of a chip-integrated sensor that maintains high sensitivity over four orders of magnitude of cantilever stiffness, expanding AFM capabilities.

Findings

Achieved displacement sensitivity of ~1 fm/Hz^(1/2).

Supported a broad stiffness range from 0.01 N/m to 290 N/m.

Operated at high mechanical frequencies (>250 kHz).

Abstract

We report on progress in developing compact sensors for atomic force microscopy (AFM), in which the mechanical transducer is integrated with near-field optical readout on a single chip. The motion of a nanoscale, doubly-clamped cantilever was transduced by an adjacent high quality factor silicon microdisk cavity. In particular, we show that displacement sensitivity on the order of 1 fm/(Hz)^(1/2) can be achieved while the cantilever stiffness is varied over four orders of magnitude (\approx 0.01 N/m to \approx 290 N/m). The ability to transduce both very soft and very stiff cantilevers extends the domain of applicability of this technique, potentially ranging from interrogation of microbiological samples (soft cantilevers) to imaging with high resolution (stiff cantilevers). Along with mechanical frequencies (> 250 kHz) that are much higher than those used in conventional AFM probes of similar stiffness, these results suggest that our cavity optomechanical sensors may have application in a wide variety of high-bandwidth AFM measurements.