Simulation of nanoparticle enhanced diffraction grating biosensor using DDA

We present the discrete dipole approximation (DDA) simulation of light scattering from bead enhanced grating to determine the relationship between the number of beads forming the grating and diffraction intensities of first and zero orders. The models of grating are prepared by volume slicing and image processing while the spatial locations of the beads are randomly computed using discrete probability distribution. The effect of bead reduction on far-field scattering of 632.8 nm incident field, from fully occupied gratings to very coarse gratings, are studied for various bead materials. The results of simulations show excellent qualitative similarities with published experimental observations and establish that bead-based grating may be used for rapid detection of small amounts of biomolecules.