Imaging properties of surface-enhanced coherent anti-Stokes Raman scattering microscopy on thin gold films

Abstract

In a wide-field surface-enhanced coherent anti-Stokes Raman scattering (SE-CARS) microscope, the sample is driven by surface plasmon polaritons supported on a thin gold film. Subsequent radiation at the anti-Stokes frequency is coupled through the gold layer onto a far-field camera, enabling the recording of surface-enhanced CARS images of structures in close proximity to the gold surface. The effective enhancement of the CARS signal can be as high as seven orders of magnitude, allowing CARS imaging at extraordinarily low light levels. In this work, we analyze the imaging properties of the SE-CARS microscope in detail, which are markedly different from the imaging properties of a point-scanning CARS microscope. Using a dipole model to describe the sample, we show that the strength of the signal and the appearance of coherent artifacts depend strongly on the geometry of the sample. We explain the observed radiation profile in the back focal plane and discuss representative imaging examples.