Nanopore tomography of a laser focus

Area of Science:

• Physics
• Physical Chemistry
• Nanotechnology

Background:

• Accurate characterization of laser focus is crucial for microscopy and nanofluidic applications.
• Existing methods for measuring laser intensity profiles often lack nanometer resolution or require optical elements.

Purpose of the Study:

• To demonstrate a novel technique for measuring the 3D laser focus intensity profile using ionic current in a nanopore.
• To quantitatively assess laser-induced temperature changes in aqueous solutions with high spatial resolution.

Main Methods:

• Utilizing a solid-state nanopore to detect changes in ionic current.
• Correlating ionic current variations with laser power to determine temperature increases.
• Reconstructing 3D temperature profiles via tomographic analysis of 2D measurements.

Main Results:

• Established a linear relationship between ionic current and laser power, indicating temperature-dependent current changes.
• Measured local temperature increases up to 20 K at the laser focus center (1064 nm wavelength).
• Achieved nanometer-resolution mapping of the 3D temperature distribution of the laser focus.

Conclusions:

• The ionic current through a nanopore provides a label-free, optical-element-free method for 3D laser focus characterization.
• This technique enables precise measurement of optical intensity and temperature distributions in aqueous environments.
• The method offers a new tool for fundamental studies in optics, nanofluidics, and laser-matter interactions.