کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1547125 | 997629 | 2008 | 6 صفحه PDF | دانلود رایگان |
In this paper, we propose an interpretation for an abnormal anti-Stokes Raman emission observed on nanometric thin films of different materials and in particular carbon nanotubes. We demonstrate that under a tight-focusing of the excitation light, a coherent anti-stokes Raman scattering (CARS) emission is produced, resulting from a wave mixing process between the incident laser light (ωl) and Stokes Raman light (ωs) generated by a surface enhanced Raman scattering (SERS) mechanism. Although the Stokes/anti-Stokes intensity ratio has been explained differently, we present here the results which corroborate the CARS emission. They can be summarized as follows: (i) a square relationship between the CARS signal intensity and the film thickness; (ii) a square relationship between the CARS signal intensity and the exciting laser intensity; (iii) a dependence of the CARS intensity on the numerical aperture (NA) of the microscope objective used for the detection of the anti-Stokes emission. Such effects are not specific to carbon nanotubes and have been observed with other materials accommodated in similar conditions on rough metallic surfaces acting as SERS supports.
Journal: Physica E: Low-dimensional Systems and Nanostructures - Volume 40, Issue 7, May 2008, Pages 2380–2385