POYNTING VECTORS AND ELECTRIC-FIELD DISTRIBUTIONS IN SIMPLE DIELECTRIC GRATINGS

We discuss, with illustrations drawn from the simple example of a diel ectric grating under total internal reflection illumination, the use o f electric field, energy density and Poynting vector as tools for unde rstanding phenomena associated with dielectric gratings. The electric field has greatest direct observational interest and exhibits patterns of nodes and antinodes that are both expected and intuitive. The ener gy density, although not directly linked with photoelectric response, has readily understood global patterns. The Poynting vector has more e laborate structure, involving patterns of curls, but the patterns are sensitive to small changes in illumination angle or groove depth. Plot s of Poynting vectors may not be as useful for dielectric structures a s they are for metals.