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. Building upon previous work in which the motion of a nanoscale, doubly-clamped cantilever (sub-pg effective mass, 2.2 MHz frequency, and stiffness ≈ 0.14 N/m) was transduced with sub-fm/Hz1/2 displacement sensitivity by an adjacent high quality factor silicon microdisk cavity, here, we show that simple modifications to the system geometry allow us to extend our sensing platform to a wide range of cantilever stiffness. In particular, we show that fm/Hz1/2 (or better) displacement sensitivity can be achieved while the cantilever stiffness is varied over four orders of magnitude (≈0.01 N/m to ≈290 N/m). The ability to transduce both very soft and very stiff cantilevers extends the range 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.
Citation: Optics Express
Pub Type: Journals
Lasers and laser optics: Microcavities, Microscopy: Scanning microscopy, Optical devices: optical microelectromechanical devices