Surface Plasmon Resonance Angle Calculator
Kretschmann Surface Plasmon Resonance Stack
A thin Au film on a high-index BK7 prism couples p-polarized light into a surface plasmon at the Au/analyte interface, producing a sharp angular reflectance dip near 0.633 μm.
Why This Design Works
In the Kretschmann geometry, p-polarized light through a prism creates an evanescent field across a thin metal film. When the prism-side in-plane wavevector matches the surface-plasmon wavevector at the metal/analyte boundary, energy couples into the plasmon mode and p-reflectance drops. Changing analyte index shifts that matching angle, which is the sensing signal.
The left side is the parallel photon wavevector normalized by \(k_0\); the right side is the Au/analyte plasmon wavevector. With BK7, Au at 0.633 μm, and water-like analyte \(n_d = 1.33\), this estimate places the p-polarized resonance in the low-70-degree range; the finite Au film and loss set the exact dip depth.