Very-high-frequency probes for atomic force microscopy with silicon optomechanics

Area of Science:

• Nanoscience and Nanotechnology
• Physics
• Engineering

Background:

• Atomic Force Microscopy (AFM) is crucial for nanosciences, enabling nanoscale force measurements.
• Existing AFM probes operate at frequencies significantly lower than 100 MHz.
• Cavity optomechanics and micro/nanoelectromechanical systems offer potential for enhanced AFM capabilities.

Purpose of the Study:

• To fabricate a novel sensor for dynamic mode AFM operating above 100 MHz.
• To achieve force measurements at unexplored timescales.
• To demonstrate AFM force-distance measurements with enhanced sensitivity and stability.

Main Methods:

• Fabrication of an optomechanical sensor using very-large-scale integration (VLSI) and photonic silicon circuits.
• Coupling an optomechanical ring cavity to a 1.55 μm laser.
• Utilizing a 130 MHz mechanical resonance mode with a quality factor of 900 in air.

Main Results:

• Achieved a displacement detection limit of 3 × 10⁻¹⁶ m/√Hz.
• Enabled detection of Brownian motion and picometer-range vibration amplitudes.
• Demonstrated stable closed-loop AFM operation with a 4 nN/nm setpoint and subpicometer amplitude.

Conclusions:

• The developed optomechanical sensor significantly surpasses commercial AFM probe frequencies.
• The sensor facilitates force sensing at unprecedented timescales and with high sensitivity.
• This technology paves the way for new AFM applications requiring picometer-level precision and dynamic measurements.