Combining grating-coupled illumination and image recognition for stable and localized optical scanning tunneling...

Area of Science:

• Atomic-scale physics
• Nanophotonics
• Surface science

Background:

• Combining scanning tunneling microscopy (STM) with optical excitation aims to study light-matter interactions at the atomic scale.
• Femtosecond laser systems enable high temporal resolution in these studies.
• Nanofocusing using optical antennas offers localized optical excitation but is limited by laser-induced thermal instabilities.

Purpose of the Study:

• To present a versatile solution for overcoming thermal instabilities in laser-excited STM experiments.
• To enable high-resolution STM under intense optical excitation with femtosecond pulses.

Main Methods:

• Actively coupling the laser and STM setup, bypassing traditional vibration-isolation systems.
• Utilizing optical image recognition to monitor the tunneling junction's position.
• Compensating for relative movement between the microscope and laser setup at up to 10 Hz by adjusting the beamline.

Main Results:

• Achieved stabilization of the optical focus position with high precision (<1 μm) over extended periods (>1 h).
• Successfully enabled high-resolution STM imaging under intense femtosecond laser excitation.
• Bypassed vibration-isolation without compromising its effectiveness.

Conclusions:

• The developed active coupling method provides a stable platform for nanoscale light-matter interaction studies.
• This approach overcomes previous limitations caused by thermal drift, paving the way for advanced atomic-scale optical experiments.