Broadband plasmonic-enhanced forward and backward multiplex coherent anti-Stokes Raman scattering microscopy

Coherent anti-Stokes Raman scattering (CARS) microscopy is an attractive technique for label-free biochemical-specific characterization of biological specimens. However, it has very low sensitivity in monitoring and imaging molecules present in extremely low concentrations or at fast speeds. To improve this sensitivity, especially for multiplex CARS, the intensity of the pump beam and broadband Stokes beam should be enhanced simultaneously. Therefore, the gold shell particle and gold surface are demonstrated to enhance the forward and backward CARS, respectively. Results show that a signal enhancement factor of ∼25,000 can be achieved for the gold surface and an even higher enhancement factor can be achieved for the gold shell particles. Thus, we can obtain an enhanced CARS signal in a broad spectral range, which will substantially improve the detection sensitivity of hyperspectral CARS spectroscopy and imaging.