Surface imaging in near-field optical microscopy by using the fluorescence decay rate: a theoretical study

Area of Science:

• Surface science and nanophotonics.
• Molecular spectroscopy and optical microscopy.

Background:

• Understanding molecular behavior near surfaces is crucial for advanced optical techniques.
• Corrugated interfaces significantly influence light-matter interactions.

Purpose of the Study:

• To investigate the fluorescence decay rate of molecules positioned above corrugated surfaces.
• To analyze how lateral molecular position affects fluorescence decay rates.
• To establish a link between surface topography and decay rate variations.

Main Methods:

• Utilized a perturbative Rayleigh method to calculate the diffracted field from a dipole source above a corrugated interface.
• Developed a transfer function to connect surface profile with fluorescence decay rate variations.
• Performed numerical calculations for dielectric and metallic samples.

Main Results:

• Demonstrated that fluorescence decay rate variations are directly related to the surface profile via a transfer function.
• Generated theoretical images of decay rate variations with up to 20% visibility.
• Achieved sufficient image resolution for potential application in life-time scanning near-field optical microscopy.

Conclusions:

• The fluorescence decay rate of molecules above corrugated interfaces is sensitive to lateral position and surface topography.
• The developed transfer function provides a quantitative link between surface features and molecular fluorescence.
• This method shows promise for high-resolution surface imaging using molecular fluorescence lifetime.