Theoretical analysis of obliquely excited surface plasmon self-interference

Area of Science:

• Physics
• Optics
• Condensed Matter Physics

Background:

• Surface plasmon polaritons (SPPs) are crucial for nanoscale light manipulation.
• Understanding SPP behavior under oblique incidence is essential for advanced optical applications.
• Previous studies often focused on normal incidence, limiting insights into off-normal excitation dynamics.

Purpose of the Study:

• To theoretically analyze surface plasmon polaritons (SPPs) excited by a tightly focused light beam at oblique incidence.
• To introduce and define a critical oblique angle (θ(co)) governing SPP characteristics.
• To investigate the influence of obliquity direction (parallel and perpendicular to polarization) on SPP resonance.

Main Methods:

• Development of a geometrical model to describe SPP evolution with increasing obliquity.
• Derivation of integral expressions for transmitted SPP fields using angular spectrum representation.
• Application of rotation matrix transformations for analyzing oblique incidence effects.

Main Results:

• Introduction of the critical oblique angle (θ(co)) as a key parameter for SPP stability, efficiency, and lateral resolution.
• Demonstration of distinct SPP self-interference resonance behaviors at parallel and perpendicular obliquities relative to θ(co).
• Observation that resonance is lost at incident angles below θ(co) for parallel obliquity and above θ(co) for perpendicular obliquity.

Conclusions:

• The critical oblique angle (θ(co)) significantly dictates the excitation and behavior of SPPs under oblique incidence.
• The direction of obliquity relative to the polarization plane critically influences SPP resonance conditions.
• This theoretical framework provides a foundation for designing optical devices that utilize SPPs with controlled oblique excitation.