Coherence preservation during light-surface plasmon polaritons-light transformation

We constructed a four-layer system composed of a prism, a silver film, an air layer and a lithium niobate crystal. Initially we used two coherent light beams to excite surface plasmons. The surface plasmons were then decoupled into light in the photorefractive crystal where a holographic grating was recorded. The two beams remained coherent through light to surface plasmons to light transformation. Studying the characteristics of the holographic grating we found out that the thickness of the grating was to the order of hundreds of microns. The thick holographic grating suggests that the holographic recording in the photorefractive materials was induced by the leaky waves rather than by surface plasmon polaritons directly.