Electromagnetic theory of surface-enhanced Raman scattering for binary silver grating with nanometer dimensions

Grating-type substrates with nanometer dimensions offer the possibility of enhancing the electromagnetic field close to surface. Binary silver grating has been used to investigate the Surface-enhanced Raman Scattering (SERS). This paper describes the electromagnetic theory of SERS effect on the surface of a binary silver grating with nanometer dimension and discusses the TM-polarized incident light because surface plasmons excitation require this polarization . Laplacian's equation is given for this model in the grating region. We use the rigorous coupled wave analysis (RCWA) to solve the Maxwell differential equations in the grating region . The consideration of optimum incident angles for different gratings is also shown by analyzing the surface plasmon (SP) excitation . SERS enhancement factor is considered for binary grating with respect to the influence of angle incidence, grating depth and ratio of grating ridge width to grating period on both surface plasmon and SERS enhancement factor. Compared with the other SERS surface models, such as the isolated spheres model and other irregular models, this one-dimension regular model allows more quantitative estimates of the surface structures for the SERS effect.