Enhanced Raman scattering in colloidal photonic crystals: A theoretical analysis

We present a theoretical method that can be used to evaluate the relative intensity of Raman scattering in photonic crystals composed of dielectric spheres. This method employs the vector spherical wave expansion of the electromagnetic wave and the layer-by-layer S-matrix formalism. By evaluating the local electric field intensity inside the photonic crystal and the dipole radiation intensity at a far-field observation point, we can calculate the enhancement factor of Raman scattering in photonic crystals. We show that the Raman intensity can be greatly enhanced by exciting photonic band modes at high frequencies (typically, the vacuum wavelength is comparable to the lattice constant) where multiple photonic bands coexist.