Ultra stable tuning fork sensor for low-temperature near-field spectroscopy

Area of Science:

• Physics
• Materials Science
• Nanotechnology

Background:

• Scanning near-field optical microscopy (SNOM) requires precise distance control for high-resolution imaging.
• Traditional SNOM systems often rely on complex piezoelectric actuators for distance control.
• Operating SNOM at cryogenic temperatures, especially in liquid helium, presents significant engineering challenges.

Purpose of the Study:

• To develop a novel, compact, and stable distance control system for low-temperature SNOM.
• To utilize a quartz tuning fork as a shear force sensor for precise distance control.
• To enable SNOM operation in liquid helium environments without proximity electronics.

Main Methods:

• A quartz tuning fork was configured with an optical fiber to act as a shear force sensor.
• The tuning fork was electrically dithered using an applied alternating voltage, eliminating the need for a separate driving piezo.
• The system's performance was evaluated in terms of approach sensitivity and quality factor at cryogenic temperatures.

Main Results:

• Achieved an approach sensitivity of 0.2 nm in the distance control system.
• Obtained high quality factors for the tuning fork sensor, reaching up to 2850.
• Demonstrated stable operation for several hours at 5 K, suitable for liquid helium environments.
• Confirmed the absence of required electronic components near the sensor, facilitating use in extreme conditions.

Conclusions:

• The developed quartz tuning fork-based distance control system offers a compact and effective solution for low-temperature SNOM.
• The system's design allows for operation in liquid helium, overcoming previous limitations.
• This advancement enables more accessible and stable high-resolution imaging in cryogenic SNOM applications.