Point Spread Function of Objective-Based Surface Plasmon Resonance Microscopy.

Area of Science:

• Optics and Photonics
• Materials Science
• Nanotechnology

Background:

• Surface Plasmon Resonance Microscopy (SPRM) is an optical imaging technique mapping refractive index using surface plasmon polaritons (SPPs).
• Nanosized objects in SPRM exhibit complex wave-like patterns, unlike the dot-like point spread functions (PSFs) of other microscopies.
• Quantitative interpretation of SPRM's wave-like PSF has been challenging due to its geometrical complexity.

Purpose of the Study:

• To develop a quantitative method for interpreting the complex wave-like point spread function (PSF) in objective-based Surface Plasmon Resonance Microscopy (SPRM).
• To establish a connection between the geometrical features of SPRM's frequency-domain patterns and experimental parameters.
• To advance the understanding of SPRM's PSF and explore its potential for future detection and sensing applications.

Main Methods:

• Applied a two-dimensional Fourier transform to SPRM's wave-like patterns, revealing dual rings in the frequency domain.
• Developed a novel ring-fitting method to extract geometrical features from these dual rings.
• Correlated extracted ring features (radius, orientation, center distance, broadening) with experimental parameters like SPP wavevector, propagation direction, incident light, and SPP propagation length.

Main Results:

• The radius of the frequency-domain rings directly corresponds to the wavevector of the surface plasmon polaritons (SPPs).
• The orientation of the rings indicates the propagation direction of the SPPs.
• The distance of the ring centers relates to the parallel component of the incident light's wavevector, controlled by the incident angle.
• The ring-broadening factor is reciprocally related to the SPP propagation length.

Conclusions:

• The developed ring-fitting method provides systematic and quantitative interpretations of SPRM's frequency-domain patterns.
• This work significantly advances the fundamental understanding of the PSF in SPRM.
• The established quantitative relationships open possibilities for utilizing SPRM's frequency-domain features in advanced detection and sensing technologies.