We report experimental data that indicate an anti-Stokes Raman emission, reminiscent of coherent anti-Stokes raman scattering. It originates from a wave mixing process between the incident laser light $\left({\omega }_l\right)$ and Stokes Raman light $\left({\omega }_s\right)$ generated by a surface enhanced Raman scattering (SERS) mechanism. The variation of anti-Stokes SERS spectra of single-walled carbon nanotubes, copper phthalocyanine, and poly(bithiophene) as a function of the film thickness, the laser excitation intensity, and the numerical aperture of the microscopic objective used for collecting the scattered light demonstrate the described phenomenon.

• Received 30 August 2005

DOI:https://doi.org/10.1103/PhysRevB.72.245402