Wide cantilever stiffness range cavity optomechanical sensors for atomic force microscopy

Area of Science:

• Nanotechnology
• Optomechanics
• Microscopy

Background:

• Atomic force microscopy (AFM) traditionally uses micro-cantilevers for surface analysis.
• Existing AFM sensors face limitations in sensitivity and dynamic range for diverse sample types.
• Integrating mechanical transducers with optical readout offers potential for enhanced performance.

Purpose of the Study:

• To develop compact, chip-integrated sensors for atomic force microscopy (AFM).
• To demonstrate high displacement sensitivity across a wide range of cantilever stiffness.
• To explore the applicability of cavity optomechanical sensors in high-bandwidth AFM measurements.

Main Methods:

• Fabrication of a single chip integrating a nanoscale doubly-clamped cantilever with a silicon microdisk cavity.
• Utilizing the microdisk cavity for near-field optical readout of cantilever motion.
• Characterizing displacement sensitivity by varying cantilever stiffness over four orders of magnitude.

Main Results:

• Achieved displacement sensitivity on the order of 1 fm/(Hz)(1/2).
• Successfully transduced cantilever stiffness ranging from ≈0.01 N/m to ≈290 N/m.
• Demonstrated mechanical frequencies exceeding 250 kHz for various cantilever stiffnesses.

Conclusions:

• The developed cavity optomechanical sensors offer versatile application for both soft microbiological samples and high-resolution imaging.
• The high sensitivity and broad stiffness range extend the capabilities of AFM.
• These sensors show promise for a wide array of high-bandwidth AFM measurements.